Amphastar Pharmaceuticals (AMPH) 10-K29 Feb 242023 FY Annual reportFinancial data

Company Profile

Document And Entity Information

Document And Entity Information - USD ($)	12 Months Ended
Document And Entity Information - USD ($)	Dec. 31, 2023	Feb. 22, 2024	Jun. 30, 2023
Document and Entity Information [Abstract]
Document Type	10-K
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Document Transition Report	false
Entity File Number	001-36509
Entity Registrant Name	Amphastar Pharmaceuticals, Inc.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	33-0702205
Entity Address, Address Line One	11570 6th Street
Entity Address, City or Town	Rancho Cucamonga
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	91730
City Area Code	909
Local Phone Number	980-9484
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	AMPH
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	true
Document Financial Statement Error Correction [Flag]	false
Entity Shell Company	false
Entity Public Float			$ 1,487,116,593
Entity Common Stock, Shares Outstanding		48,095,862
Entity Central Index Key	0001297184
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	false
Auditor Name	Ernst & Young LLP
Auditor Firm ID	42
Auditor Location	Irvine, California

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Current assets:
Cash and cash equivalents	$ 144,296	$ 156,098
Restricted cash	235	235
Short-term investments	112,510	19,664
Restricted short-term investments	2,200	2,200
Accounts receivable, net	114,943	88,804
Inventories	105,833	103,584
Income tax refunds and deposits	526	171
Prepaid expenses and other assets	9,057	7,563
Total current assets	489,600	378,319
Property, plant, and equipment, net	282,746	238,266
Finance lease right-of-use assets	564	753
Operating lease right-of-use assets	32,333	25,554
Investment in unconsolidated affiliate	527	2,414
Goodwill and intangible assets, net	613,295	37,298
Long-term investments	14,685
Other assets	25,910	20,856
Deferred tax assets	53,252	38,527
Total assets	1,512,912	741,987
Current liabilities:
Accounts payable and accrued liabilities	93,366	84,242
Accrued payments for BAQSIMI	126,090
Income taxes payable	1,609	4,571
Current portion of long-term debt	436	3,046
Current portion of operating lease liabilities	3,906	3,003
Total current liabilities	225,407	94,862
Long-term reserve for income tax liabilities	6,066	7,225
Long-term debt, net of current portion and unamortized debt issuance costs	589,579	72,839
Long-term operating lease liabilities, net of current portion	29,721	23,694
Deferred tax liabilities		144
Other long-term liabilities	22,718	14,565
Total liabilities	873,491	213,329
Stockholders' equity:
Preferred stock: par value $0.0001; 20,000,000 shares authorized; no shares issued and outstanding
Common stock: par value $0.0001; 300,000,000 shares authorized; 59,390,194 and 48,068,881 shares issued and outstanding as of December 31, 2023 and 58,110,231 and 48,112,069 shares issued and outstanding as of December 31, 2022, respectively	6	6
Additional paid-in capital	486,056	455,077
Retained earnings	409,268	271,723
Accumulated other comprehensive loss	(8,478)	(8,624)
Treasury stock	(247,431)	(189,524)
Total equity	639,421	528,658
Total liabilities and stockholders' equity	$ 1,512,912	$ 741,987

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2023	Dec. 31, 2022
CONSOLIDATED BALANCE SHEETS
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock; shares authorized	300,000,000	300,000,000
Common stock; shares issued	59,390,194	58,110,231
Common stock; shares outstanding	48,068,881	48,112,069

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Net Revenues:
Total net revenues	$ 644,395	$ 498,987	$ 437,768
Cost of revenues	293,274	250,127	238,029
Gross profit	351,121	248,860	199,739
Operating expenses:
Selling, distribution, and marketing	28,853	21,531	17,486
General and administrative	51,540	45,061	51,434
Research and development	73,741	74,771	60,932
Total operating expenses	154,134	141,363	129,852
Income from operations	196,987	107,497	69,887
Non-operating income (expenses):
Interest income	5,459	1,321	601
Interest expense	(27,158)	(1,846)	(885)
Other income (expenses), net	(3,929)	9,068	14,536
Total non-operating income (expenses), net	(25,628)	8,543	14,252
Income before income taxes	171,359	116,040	84,139
Income tax provision	31,833	23,477	20,630
Income before equity in losses of unconsolidated affiliate	139,526	92,563	63,509
Equity in losses of unconsolidated affiliates	(1,981)	(1,177)	(208)
Net income attributable to Amphastar Pharmaceuticals, Inc.	137,545	91,386	63,301
Net income attributable to non-controlling interests			1,185
Net income attributable to Amphastar Pharmaceuticals, Inc.	$ 137,545	$ 91,386	$ 62,116
Net income per share
Basic (in Dollars per share)	$ 2.85	$ 1.88	$ 1.30
Diluted (in Dollars per share)	$ 2.60	$ 1.74	$ 1.25
Weighted-average shares used to compute net income per shares
Basic (in Shares)	48,265	48,551	47,777
Diluted (in Shares)	53,001	52,427	49,784
Product revenues, net
Net Revenues:
Total net revenues	$ 593,238	$ 498,987	$ 437,768
Other revenues
Net Revenues:
Total net revenues	$ 51,157

CONSOLIDATED STATEMENTS OF COMP

CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS)
Net income	$ 137,545	$ 91,386	$ 62,116
Other comprehensive income (loss), net of income taxes
Reclassification of adjustment for amounts included in net income			(362)
Foreign currency translation adjustment	298	(2,335)	(2,943)
Change in pension obligations	(152)	476	261
Total other comprehensive income (loss)	146	(1,859)	(3,044)
Total comprehensive income	$ 137,691	$ 89,527	$ 59,072

CONSOLIDATED STATEMENTS OF STOC

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Total Amphastar Stockholders' Equity [Member]	Non-controlling Interest [Member]	Total
Balance at Dec. 31, 2020	$ 5	$ 410,061	$ 117,773	$ (3,721)	$ (121,812)	$ 402,306	$ 46,417
Balance at Dec. 31, 2020								$ 448,723
Balance at Dec. 31, 2020	54,760,922				(7,265,483)
Changes in Stockholders' Equity
Net income			62,116			62,116		62,116
Other comprehensive income (loss)								(3,044)
Other comprehensive income (loss) attributable to Amphastar Pharmaceuticals, Inc.				(2,682)		(2,682)		(2,682)
Proceeds from the private placement of ANP		(22,162)	448	(362)		(22,076)	(46,641)	(68,717)
Net income (loss) attributable to non-controlling interest							1,185	1,185
Purchase of treasury stock					$ (28,873)	(28,873)		(28,873)
Purchase of treasury stock (in Shares)					(1,477,305)
Issuance of treasury stock in connection with the Company's equity plans		(206)			$ 206
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					17,498
Issuance of common stock in connection with the Company's equity plans	$ 1	15,924				15,925		15,925
Issuance of common stock in connection with the Company's equity plans (in Shares)	1,679,280
Share-based compensation expense		18,806				18,806	$ (961)	17,845
Balance at Dec. 31, 2021	$ 6	422,423	180,337	(6,765)	$ (150,479)	445,522
Balance at Dec. 31, 2021								445,522
Balance at Dec. 31, 2021	56,440,202				(8,725,290)
Changes in Stockholders' Equity
Net income			91,386			91,386		91,386
Other comprehensive income (loss)				(1,859)		(1,859)		(1,859)
Purchase of treasury stock					$ (39,909)	(39,909)		(39,909)
Purchase of treasury stock (in Shares)					(1,335,528)
Issuance of treasury stock in connection with the Company's equity plans		(864)			$ 864
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					62,656
Issuance of common stock in connection with the Company's equity plans		15,658				15,658		15,658
Issuance of common stock in connection with the Company's equity plans (in Shares)	1,670,029
Share-based compensation expense		17,860				17,860		17,860
Balance at Dec. 31, 2022	$ 6	455,077	271,723	(8,624)	$ (189,524)	528,658
Balance at Dec. 31, 2022								$ 528,658
Balance at Dec. 31, 2022	58,110,231				(9,998,162)			48,112,069
Changes in Stockholders' Equity
Net income			137,545			137,545		$ 137,545
Other comprehensive income (loss)				146		146		146
Purchase of treasury stock					$ (58,144)	(58,144)		(58,144)
Purchase of treasury stock (in Shares)					(1,338,757)
Issuance of treasury stock in connection with the Company's equity plans		(237)			$ 237
Issuance of treasury stock in connection with the Company's equity plans (in Shares)					15,606
Issuance of common stock in connection with the Company's equity plans		10,974				10,974		10,974
Issuance of common stock in connection with the Company's equity plans (in Shares)	1,279,963
Share-based compensation expense		20,242				20,242		20,242
Balance at Dec. 31, 2023	$ 6	$ 486,056	$ 409,268	$ (8,478)	$ (247,431)	$ 639,421
Balance at Dec. 31, 2023								$ 639,421
Balance at Dec. 31, 2023	59,390,194				(11,321,313)			48,068,881

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash Flows From Operating Activities:
Net income attributable to Amphastar Pharmaceuticals, Inc.	$ 137,545	$ 91,386	$ 63,301
Reconciliation to net cash provided by operating activities:
Loss (gain) on disposal of assets	475	141	348
Impairment of long-lived assets	2,700
Gain on deconsolidation of subsidiary			(13,587)
Gain on interest rate swaps and foreign currency transactions, net	5,330	(2,196)	27
Depreciation of property, plant, and equipment	25,205	23,815	22,196
Amortization of product rights, trademarks, and patents	12,830	954	1,071
Operating lease right-of-use asset amortization	3,742	3,506	3,266
Amortization of discounts, premium, and debt issuance costs	11,399	466	219
Equity in losses of unconsolidated affiliate	1,981	1,177	208
Share-based compensation	20,242	17,860	18,687
Changes in reserve for uncertain tax positions	(1,159)	694	1,821
Changes in deferred taxes, net	(12,578)	(16,445)	2,388
Changes in operating assets and liabilities:
Accounts receivable, net	(26,086)	(10,132)	(14,921)
Inventories	(1,724)	(11,746)	1,258
Prepaid expenses and other assets	(2,728)	(1,854)	2,927
Income tax refunds, deposits, and payable, net	(3,319)	(4,555)	8,349
Operating lease liabilities	(3,589)	(3,154)	(3,198)
Accounts payable and accrued liabilities	13,237	(736)	3,634
Net cash provided by operating activities	183,503	89,181	97,994
Cash Flows From Investing Activities:
BAQSIMI acquisition	(506,406)
Purchases and construction of property, plant, and equipment	(38,166)	(24,034)	(27,456)
Proceeds from the sale of property, plant and equipment		421
Purchase of investments	(144,556)	(35,761)	(17,375)
Maturity of investments	38,622	27,969	18,771
Deposits and other assets	(1,390)	1,372	2,612
Net cash used in investing activities	(649,116)	(32,777)	(28,672)
Cash Flows From Financing Activities:
ANP restructuring (see Note 3)			(53,592)
Proceeds from equity plans, net of withholding tax payments	10,974	15,658	15,925
Purchase of treasury stock	(58,144)	(39,909)	(28,873)
Settlement of ANP equity awards			(839)
Debt issuance costs	(25,079)	(407)	(1,738)
Repayments under lines of credit			(1,161)
Proceeds from issuance of long-term debt	845,000		70,000
Principal payments on long-term debt	(318,658)	(1,781)	(36,740)
Net cash provided by financing activities	454,093	(26,439)	(37,018)
Effect of exchange rate changes on cash	(282)	(220)	(223)
Net (decrease) increase in cash, cash equivalents, and restricted cash	(11,802)	29,745	32,081
Cash, cash equivalents, and restricted cash at beginning of period	156,333	126,588	94,507
Cash, cash equivalents, and restricted cash at end of period	144,531	156,333	126,588
Noncash Investing and Financing Activities:
Deferred payment for BAQSIMI acquisition	121,699
Capital expenditures included in accounts payable	4,454	5,256	9,488
Operating lease right-of-use assets in exchange for operating lease liabilities	10,521	2,166	11,041
Equipment acquired under finance leases		642	107
Supplemental Disclosures of Cash Flow Information:
Interest paid, net of capitalized interest	17,573	3,023	2,109
Income taxes paid	$ 49,001	$ 44,442	$ 8,096

Business

Business	12 Months Ended
Business	Dec. 31, 2023
Business
Business	Note 1. Business Amphastar Pharmaceuticals, Inc., a Delaware corporation (together with its subsidiaries, hereinafter referred to as the “Company”) is a bio-pharmaceutical company that focuses primarily on developing, manufacturing, marketing, and selling technically challenging generic and proprietary injectable, inhalation, and intranasal products, including products with high technical barriers to market entry. Additionally, the Company sells insulin active pharmaceutical ingredient, or API, products. Most of the Company’s products are used in hospital or urgent care clinical settings and are primarily contracted and distributed through group purchasing organizations and drug wholesalers. The Company’s insulin API products are sold to other pharmaceutical companies for use in their own products and are being used by the Company in the development of injectable finished pharmaceutical products. The Company’s inhalation product, Primatene MIST ®

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2023
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	Note 2. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements include the accounts of the Company and its subsidiaries, and are prepared in accordance with United States generally accepted accounting principles, or GAAP. Certain prior period amounts have been reclassified within the operating activities of the consolidated statements of cash flows to conform to the current period presentation. All intercompany activity has been eliminated in the preparation of the consolidated financial statements. In the opinion of management, the accompanying consolidated financial statements include all adjustments, which are of a normal recurring nature, necessary to present fairly the consolidated financial position, results of operations, and cash flows of the Company. The Company’s subsidiaries include: (1) International Medication Systems, Limited, or IMS, (2) Armstrong Pharmaceuticals, Inc., or Armstrong, (3) Amphastar Nanjing Pharmaceuticals Inc., or ANP, (4) Amphastar France Pharmaceuticals, S.A.S., or AFP, (5) Amphastar UK Ltd., or AUK, (6) International Medication Systems (UK) Limited, or IMS UK, and (7) Amphastar Medication Co., LLC, or Amphastar Medication. Investment in Unconsolidated Affiliate The Company applies the equity method of accounting for investments when it has significant influence, but not controlling interest in the investee. Judgment regarding the level of influence over each equity method investment includes key factors such as ownership interest, representation on the board of directors, participation in policy-making decisions and material intercompany transactions. The Company’s proportionate share of the earnings or losses resulting from these investments is reported as “Equity in losses of unconsolidated affiliate” in the accompanying consolidated statements of operations. Investments accounted for using the equity method may be reported on a lag of up to three months if financial statements of the investee are not available in sufficient time for the investor to apply the equity method as of the current reporting date. The determination of whether an investee’s results are recorded on a lag is made on an investment-by-investment basis. The carrying value of equity method investments is reported as “Investment in unconsolidated affiliate” in the accompanying consolidated balance sheets. The Company’s equity method investments are reported at cost and adjusted each period for the Company’s share of the investee’s earnings or losses and dividends paid, if any. The Company assesses equity method investments for impairment whenever events or changes in circumstances indicate that the carrying value of an investment may not be recoverable. If the decline in value is considered to be other than temporary, the investment is written down to its estimated fair value, which establishes a new cost basis in the investment. No such impairment was identified for any of the periods presented. Use of Estimates The preparation of the consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: fair value of acquired assets, determination of allowances for credit losses, fair value of financial instruments, allowance for discounts, provision for chargebacks and rebates, provision for product returns, adjustment of inventory to its net realizable value, impairment of investments, long-lived and intangible assets and goodwill, accrual for workers’ compensation liabilities, litigation reserves, stock price volatility for share-based compensation expense, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions. Foreign Currency The functional currency of the Company, its domestic subsidiaries, its Chinese subsidiary ANP, and its U.K. subsidiary, AUK, is the U.S. Dollar, or USD. ANP maintains its books of record in Chinese yuan. These books are remeasured into the functional currency of USD using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign currency exchange gains and losses are reflected in the Company’s accompanying consolidated statements of operations. The Company’s French subsidiary, AFP, maintains its book of record in euros. AUK’s subsidiary, IMS UK, maintains its book of record in British pounds. These local currencies have been determined to be the subsidiaries’ respective functional currencies. Activities in the statements of operations are translated to USD using average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature are reported in other comprehensive income (loss). The unrealized gains and losses of intercompany foreign currency transactions that are of a long-term investment nature for the years ended December 31, 2023, 2022, and 2021 were a $1.1 million gain, a $1.8 million loss, and a $2.6 million loss, respectively. Comprehensive Income (loss) The Company’s comprehensive income (loss) includes its foreign currency translation gains and losses, changes in pension obligations as well as its share of other comprehensive income from its equity method investments. Acquisitions The Company evaluates acquisitions and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and substantive processes that have the ability to create outputs, which would meet the definition of a business. Acquisitions meeting the definition of business combinations are accounted for using the acquisition method of accounting, which requires that the purchase price be allocated to the net assets acquired at their respective fair values. In a business combination, any excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. For asset acquisitions, a cost accumulation model is used to determine the cost of an asset acquisition. Direct transaction costs are recognized as part of the cost of an asset acquisition. The cost of an asset acquisition, including transaction costs, is allocated to identifiable assets acquired and liabilities assumed based on a relative fair value basis, with the exception of non-qualifying assets. Goodwill is not recognized in an asset acquisition. When a transaction accounted for as an asset acquisition includes an in-process research and development, or IPR&D, asset, the IPR&D asset is only capitalized if it has an alternative future use other than in a particular research and development project. Asset acquisitions may include contingent consideration arrangements that encompass obligations to make future payments to sellers contingent upon the achievement of future financial targets. Contingent consideration, including assumed contingent considerations, is not recognized until all contingencies are resolved and the consideration is paid or becomes payable (unless contingent considerations meets the definition of a derivative, in which case the amount becomes part of the basis in the asset acquired), at which point the consideration is allocated to the assets acquired based on their relative fair values at the acquisition date, with the exception of non-qualifying assets. Judgments are used in determining estimates of useful lives of long-lived assets. Useful life estimates are based on, among other factors, estimates of expected future net cash flows, the assessment of each asset’s life cycle, and the impact of competitive trends on each asset’s life cycle and other factors. These judgments can materially impact the estimates used to allocate purchase consideration to assets acquired and liabilities assumed, and the resulting timing and amounts charged to or recognized in current and future operating results. For these and other reasons, actual results may vary significantly from estimated results. Shipping and Handling Costs For the years ended December 31, 2023, 2022, and 2021, the Company included shipping and handling costs of approximately $7.0 million, $7.4 million and $4.3 million, respectively, in selling, distribution and marketing expenses in the accompanying consolidated statements of operations. Advertising Expense Advertising expenses, primarily associated with Primatene MIST ® Research and Development Costs Research and development costs are charged to expense as incurred and consist of costs incurred to further the Company’s research and development activities. These include salaries and related employee benefits, costs associated with clinical trials, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers. The Company may produce or purchase inventories prior to or with the expectation of receiving regulatory approval in the near term, based on operational decisions about the most effective use of existing resources. This inventory is referred to as pre-launch inventory. It is the Company’s accounting policy that the pre-launch inventory is capitalized if it has a probable future economic benefit at the time it is purchased or manufactured. If regulatory approval is received and previously expensed pre-launch inventory is sold, such sales may contribute up to a 100% margin to the Company’s operating results. Pre-launch inventory costs include cost of work in process, materials, and finished drug products. For the years ended December 31, 2023, 2022, and 2021, the Company did not have material capitalized pre-launch inventory. Financial Instruments The Company’s accompanying consolidated balance sheets include the following financial instruments: cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued expenses, short-term borrowings and long-term obligations. The Company considers the carrying amounts of current assets and liabilities on the consolidated balance sheets to approximate the fair value of these financial instruments due to the short maturity of these items. The carrying value of the Company’s long-term obligations, with the exception of the convertible debt (See Note 15) approximates their fair value, as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. Investments and short-term investments are recorded at fair value based on quoted prices from recognized security exchanges and other methods (See Note 9). The Company at times enters into interest rate swap contracts to manage its exposure to interest rate changes and its overall cost of long-term debt. The Company’s interest rate swap contracts exchange the variable interest rates for fixed interest rates. From time to time, the Company may enter into forward currency contracts to lock in currency exchange rates to manage its foreign currency exchange rate exposure. The Company’s interest rate swaps and forward currency contracts have not been designated as hedging instruments and, therefore are recorded at their fair values at the end of each reporting period with changes in fair value recorded in other income (expenses) on the consolidated statements of operations. As of December 31, 2023, the Company did not have any unsettled forward currency contracts to purchase foreign currency. As of December 31, 2022, the Company had an unsettled forward currency contract to purchase foreign currency with a fair value of approximately $0.2 million based on Level 2 inputs, which was recorded as a liability in accounts payable and accrued liabilities in the accompanying consolidated balance sheets. Cash and Cash Equivalents Cash and cash equivalents consist of cash, money market accounts, certificates of deposit and highly liquid investments with original maturities of three months or less. Investments Investments as of December 31, 2023 and 2022 consisted of certificates of deposit and investment grade corporate, agency, and municipal bonds with original maturity dates between three and fifteen months. Restricted Cash Restricted cash is collateral required for the Company to guarantee certain vendor payments in France. As of December 31, 2023 and 2022, the restricted cash balance was $0.2 million. Restricted Short-Term Investments Restricted short-term investments consist of certificates of deposit that are collateral for standby letters of credit to qualify for workers’ compensation self-insurance. The certificates of deposit have original maturities greater than three months, but less than one year. As of December 31, 2023 and 2022, the balance of restricted short-term investments was $2.2 million. Allowance for Credit Losses The Company evaluates the collectability of accounts receivable based on a combination of factors. When the Company is aware of circumstances that may impair a customer’s ability to pay subsequent to the original sale, the Company records a specific allowance to reduce the amounts receivable to the amount that the Company reasonably believes to be collectable. For all other customers, the Company recognizes an allowance for credit losses based on factors that include the length of time the receivables are past due, industry and geographic concentrations, the current economic conditions and historical collection experience. As of December 31, 2023 and 2022, the Company's allowance for credit losses was $2.8 million and $2.7 million, respectively. Inventories Inventories consist of currently marketed products and products manufactured under contract. Inventories are stated using the first-in, first-out method, on a consistent basis. The Company states inventory at the lower of cost or net realizable value. Provisions are made for slow moving, unsellable, or obsolete items. Net realizable value is determined using the estimated selling price, in the ordinary course of business, less estimated costs to complete and dispose. Property, Plant and Equipment Property, plant and equipment are stated at cost or, in the case of assets acquired in a business combination, at fair value on the purchase date. Depreciation and amortization expense is computed using the straight-line method over the estimated useful lives of the related assets as follows: Buildings 20 - 31 years Machinery and equipment 3 - 12 years Furniture and fixtures 3 - 7 years Automobiles 4 - 5 years Leasehold improvements Lesser of remaining lease term or useful life Intangible Assets Intangible assets with finite lives are amortized using the straight-line method over the period the asset is expected to contribute directly or indirectly to the future cash flows of the Company as follows: Product rights 10 - 24 years Patents 10 - 20 years Land-use rights 37 - 50 years Impairment of Long-Lived Assets, including Identifiable Definite-Lived Intangible Assets The Company assesses long-term and identifiable definite-lived intangible assets or asset groups for impairment when events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. If the sum of the expected future undiscounted cash flows is less than the carrying amount of the asset or an asset group, further impairment analysis is performed. An impairment loss is measured as the amount by which the carrying amount of the asset or asset groups exceeds the fair value (assets to be held and used) or fair value less cost to sell (assets to be disposed of). The Company also assesses the useful lives of its assets periodically to determine whether events and circumstances warrant a revision to the remaining useful life. Changes in the useful life are adjusted prospectively by revising the remaining period over which the asset is amortized. Deferred Income Taxes The Company utilizes the liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized. Debt Issuance Costs Debt issuance costs related to non-revolving debt are recognized as a reduction to the related debt balance in the accompanying consolidated balance sheets and amortized to interest expense over the contractual term of the related debt using the effective interest method. Debt issuance costs associated with revolving debt are capitalized within other long-term assets on the consolidated balance sheets and are amortized to interest expense over the term of the related revolving debt. Convertible Debt The Company accounts for its convertible debt instruments as a single unit of accounting, a liability, because the Company concluded that the conversion features do not require bifurcation as a derivative under Accounting Standards Codification, or ASC, 815-15, Derivatives and Hedging In accordance with ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) Debt with Conversion and Other Options Impairment of Indefinite-Lived Intangible Asset and Goodwill The Company assesses indefinite lived intangible asset and goodwill for impairment in the fourth quarter of each year or more frequently if indicators of impairment are present. When the Company chooses to perform a qualitative assessment, it evaluates economic, industry and company-specific factors as an initial step. If the Company determines it is more likely than not that the indefinite-lived intangible asset is impaired or the fair value of a reporting unit is less than its carrying amount, further quantitative impairment testing is then performed; otherwise, no further testing is required. An impairment loss is recorded if the asset’s fair value is less than its carrying value. The Company also periodically assesses its indefinite-lived intangible asset to determine if events and circumstances continue to support an indefinite useful life. If the life is no longer indefinite, the asset is tested for impairment. The carrying value, after recognition of any impairment loss, is amortized over its remaining useful life. Self-Insured Claims The Company is self-insured, up to certain limits, for workers’ compensation claims. The Company has purchased stop-loss insurance, which will reimburse the Company for individual claims in excess of $350,000 or aggregate minimum attachment of $4.8 million annually. The cost of claims reported and an estimate of claims incurred but not reported are charged to operating expenses. A liability for unpaid claims and the associated claim expenses, including incurred but not reported losses, is actuarially determined and reflected in accrued liabilities in the accompanying consolidated balance sheets. Total expense under the program was approximately $1.7 million, $0.3 million, and $0.5 million, for the years ended December 31, 2023, 2022 and 2021, respectively. The self-insured claims liability was $4.3 million and $3.7 million at December 31, 2023 and 2022, respectively. The determination of such claims and expenses and the appropriateness of the related liability is reviewed periodically and updated, as necessary. Changes in estimates are recorded in the period identified. Litigation, Commitments and Contingencies Litigation, commitments and contingencies are accrued when management, after considering the facts and circumstances of each matter as then known to management, has determined it is probable a liability will be found to have been incurred and the amount of the loss can be reasonably estimated. When only a range of amounts is reasonably estimable and no amount within the range is more likely than another, the low end of the range is recorded. Legal fees are expensed as incurred. Due to the inherent uncertainties surrounding gain contingencies, the Company generally does not recognize potential gains until they are realized. In 2021, the Company settled a legal dispute with an unaffiliated third party and subsequently received a settlement payment, net of contingent legal fees, in the amount of $2.7 million. The net amount of $2.7 million was recorded as other income in other income (expense), net in the consolidated statements of operations for the year ended December 31, 2021. Recent Accounting Pronouncements In November 2023, the Financial Accounting Standards Board, or FASB, issued Accounting Standard Update 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures In December 2023, the FASB issued Accounting Standard Update 2023-09, Income taxes (Topic 740): Improvements to Income Tax Disclosures

ANP Restructuring

ANP Restructuring	12 Months Ended
ANP Restructuring	Dec. 31, 2023
ANP Restructuring
ANP Restructuring	Note 3. ANP Restructuring As a result of the ANP restructuring that was completed during the third quarter of 2021, and subsequent investments by other equity holders of Hanxin Pharmaceutical Technology Co., Ltd, or Hanxin, the Company has a 11.5% noncontrolling investment in Hanxin as of December 31, 2023. In addition to the retained noncontrolling investment in Hanxin, the Company maintains a seat on Hanxin’s board of directors, and Henry Zhang, a relative of Dr. Jack Zhang, the Company’s Chief Executive Officer and Dr. Mary Luo, the Company’s Chief Operating Officer, is an equity holder, general manager, and chairman of the board of directors of Hanxin. As a result, it was determined that the Company has significant influence over Hanxin and as such the retained noncontrolling investment in Hanxin is accounted for as an equity method investment. Hanxin continues to be a related party after the deconsolidation.

BAQSIMI Acquisition

BAQSIMI Acquisition	12 Months Ended
BAQSIMI Acquisition	Dec. 31, 2023
BAQSIMI Acquisition
BAQSIMI Acquisition	Note 4. BAQSIMI ® Acquisition On June 30, 2023, the Company completed its acquisition of BAQSIMI ® ® closing. The Company is also required to pay Lilly $4.0 million upon the assignment of certain contracts to the Company after the first anniversary of the Closing, but no later than 18 months after the Closing. The Company may also be required to pay additional contingent consideration of up to $450.0 million to Lilly based on the achievement of certain milestones. The Purchase Agreement provides that the contingent consideration that may become payable to Lilly would be achieved as follows: (i) a one-time payment of $100.0 million if the Company achieves annual net sales of $175.0 million or more of BAQSIMI ® and certain related products, or the Milestone Products, in any one year during the first five years after the Closing; (ii) up to two payments of $100.0 million each if the Company achieves annual net sales of $200.0 million or more of Milestone Products in any one year during the first five years after the Closing; and (iii) a one-time payment of $150.0 million if the Company achieves total cumulative net sales of $950.0 million or more of the Milestone Products for the first five years after the Closing. In addition, the Company assumed certain contingent consideration of Lilly, which would require the Company to pay up to an aggregate of $125.0 million based on the achievement of annual net sales milestones of $350.0 million, $400.0 million and $600.0 million. The Company has accounted for the BAQSIMI ® Business Combination ® ® ® The relative fair values of identifiable assets from the acquisition of BAQSIMI ® Manufacturing Services Agreement In connection with the Closing, the Company entered into a Manufacturing Services Agreement, or the MSA, with Lilly, pursuant to which Lilly has agreed, for a period of time not to exceed 18 months , to provide certain manufacturing, packaging, labeling and supply services for BAQSIMI ® directly or through third-party contractors to the Company in connection with its operation of the development, manufacture, and commercialization of BAQSIMI ® . Upon termination of the MSA, the Company will be obligated to purchase all API, components, and finished goods on hand at prices agreed upon in the MSA. Transition Services Agreement In connection with the Closing, the Company entered into a Transition Services Agreement, or the TSA, with Lilly pursuant to which Lilly has agreed, for a period of time not to exceed 18 months , to provide certain services to the Company to support the transition of BAQSIMI ® operations to the Company, including with respect to the conduct of certain clinical, regulatory, medical affairs, and commercial sales channel activities. The following table summarizes the aggregate amount paid for the assets acquired by the Company in connection with the acquisition of BAQSIMI ® Fair Value (in thousands) Cash payment $ 500,000 Fair value of deferred cash payments 121,699 Transaction costs 6,406 Total purchase price $ 628,105 The total purchase price was allocated to the acquired assets based on their relative fair values, as follow: Fair Value (in thousands) Property, plant, and equipment $ 34,426 BAQSIMI ® 591,338 Deferred tax assets 2,341 Total assets acquired $ 628,105 The Company is amortizing the acquired intangible asset on a straight line basis over its estimated useful life of 24 years (See Note 11 for additional information). The fair value of the deferred cash payment is being accreted to the full $129.0 million amount over a one-year period through interest expense. During the year ended December 31, 2023 $3.7 million of interest expense was recognized related to accretion of the deferred cash payments. Credit Agreement On June 30, 2023, in conjunction with the Company’s acquisition of BAQSIMI ® The Credit Agreement provides for a senior secured term loan, or the Wells Fargo Term Loan in an aggregate principal amount of $500.0 million. The Wells Fargo Term Loan matures on the June 30, 2028. The Credit Agreement also provides a senior secured revolving credit facility, or the Revolving Credit Facility, in an aggregate principal amount of $200.0 million. The Revolving Credit Facility matures on June 30, 2028. As of December 31, 2023, the Company had no borrowings outstanding under the Revolving Credit Facility. Proceeds from the Term Loan were used to finance the acquisition of BAQSIMI ®

Revenue Recognition

Revenue Recognition	12 Months Ended
Revenue Recognition	Dec. 31, 2023
Revenue Recognition
Revenue Recognition	Note 5. Revenue Recognition Product revenues, net In accordance with ASC 606 Revenue from Contracts with Customers Generally, revenue is recognized at the time of product delivery to the Company’s customers. In some cases, revenue is recognized at the time of shipment when stipulated by the terms of the sale agreements. The consideration the Company receives in exchange for its goods or services is only recognized when it is probable that a significant reversal will not occur. The consideration to which the Company expects to be entitled includes a stated list price, less various forms of variable consideration. The Company makes significant estimates for related variable consideration at the point of sale, including chargebacks, rebates, product returns, other discounts and allowances. The Company’s payment terms vary by types and locations of customers and the products or services offered. Payment terms differ by jurisdiction and customers, but payment is generally required in a term ranging from 30 to 75 days from date of shipment or satisfaction of the performance obligation. For certain products or services and certain customer types, the Company may require payment before products are delivered or services are rendered to customers. Provisions for estimated chargebacks, rebates, discounts, product returns and credit losses are made at the time of sale and are analyzed and adjusted, if necessary, at each balance sheet date. Revenues derived from contract manufacturing services are recognized when third-party products are shipped to customers. The Company’s accounting policy is to review each agreement involving contract development and manufacturing services to determine if there are multiple revenue-generating activities that constitute more than one unit of accounting. Revenues are recognized for each unit of accounting based on revenue recognition criteria relevant to that unit. The Company does not have any revenue arrangements with multiple performance obligations. Service revenues derived from research and development contracts are recognized over time based on progress toward satisfaction of the performance obligation. For each performance obligation satisfied over time, the Company assesses the proper method to be used for revenue recognition, either an input method to measure progress toward the satisfaction of services or an output method of determining the progress of completion of performance obligation. Revenue from research and development services at ANP was $4.5 million, $4.3 million and $5.1 million for the years ended December 31, 2023, 2022 and 2021, respectively. Other revenues Revenues related to sales of BAQSIMI ® Provision for Chargebacks and Rebates The provision for chargebacks and rebates is a significant estimate used in the recognition of revenue. Wholesaler chargebacks relate to sales terms under which the Company agrees to reimburse wholesalers for differences between the gross sales prices at which the Company sells its products to wholesalers and the actual prices of such products that wholesalers resell under the Company’s various contractual arrangements with third parties such as hospitals and group purchasing organizations in the United States. Rebates include primarily amounts paid to retailers, payers, and providers in the United States, including those paid to state Medicaid programs, and are based on contractual arrangements or statutory requirements. The Company estimates chargebacks and rebates using the expected value method at the time of sale to wholesalers based on wholesaler inventory stocking levels, historic chargeback and rebate rates, and current contract pricing. The provision for chargebacks and rebates is reflected as a component of net revenues. The following table is an analysis of the chargeback and rebate provision: Year Ended December 31, 2023 2022 (in thousands) Beginning balance $ 26,606 $ 20,167 Provision for chargebacks and rebates 257,219 208,081 Credits and payments issued to third parties (255,905) (201,642) Ending balance $ 27,920 $ 26,606 Changes in the chargeback provision from period to period are primarily dependent on the Company’s sales to its wholesalers, the level of inventory held by wholesalers, and the wholesalers’ customer mix. Changes in the rebate provision from period to period are primarily dependent on retailers’ and other indirect customers’ purchases. The approach that the Company uses to estimate chargebacks has been consistently applied for all periods presented. Variations in estimates have been historically small. The Company continually monitors the provision for chargebacks and rebates and makes adjustments when it believes that the actual chargebacks and rebates may differ from the estimates. The settlement of chargebacks and rebates generally occurs within 20 days to 60 days after the sale to wholesalers. Accounts receivable and/or accounts payable and accrued liabilities are reduced and/or increased by the chargebacks and rebate amounts depending on whether the Company has the right to offset with the customer. The provision for chargebacks and rebates is included in the following balance sheet accounts: December 31, 2023 2022 (in thousands) Reduction to accounts receivable, net $ 21,861 $ 20,460 Accounts payable and accrued liabilities 6,059 6,146 Total $ 27,920 $ 26,606 Accrual for Product Returns The Company offers most customers the right to return qualified excess or expired inventory for partial credit; however, API product sales are generally non-returnable. The Company’s product returns primarily consist of the returns of expired products from sales made in prior periods. Returned products cannot be resold. At the time product revenue is recognized, the Company records an accrual for product returns estimated using the expected value method. The accrual is based, in part, upon the historical relationship of product returns to sales and customer contract terms. The Company also assesses other factors that could affect product returns including market conditions, product obsolescence, and new competition. Although these factors do not normally give the Company’s customers the right to return products outside of the regular return policy, the Company realizes that such factors could ultimately lead to increased returns. The Company analyzes these situations on a case-by-case basis and makes adjustments to the product return reserve as appropriate. The provision for product returns is reflected as a component of net revenues. The following table is an analysis of the product return liability: Year Ended December 31, 2023 2022 (in thousands) Beginning balance $ 19,451 $ 21,677 Provision for product returns 4,275 4,405 Credits issued to third parties (6,547) (6,631) Ending balance $ 17,179 $ 19,451 The provision for product returns is included in the following balance sheet accounts: December 31, 2023 2022 (in thousands) Accounts payable and accrued liabilities $ 12,263 $ 14,867 Other long-term liabilities 4,916 4,584 Total $ 17,179 $ 19,451 For the years ended December 31, 2023 and 2022, the Company’s aggregate product return rate was 1.1% and 1.4% of qualified sales, respectively.

Income per Share Attributable t

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders	12 Months Ended
	Dec. 31, 2023
Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders
Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders	Note 6. Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders Basic net income per share attributable to Amphastar Pharmaceuticals Inc. stockholders is calculated based upon the weighted-average number of shares outstanding during the period. Diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders gives effect to all potentially dilutive shares outstanding during the period, such as stock options, non-vested restricted stock units, and shares issuable under the Company’s Employee Stock Purchase Plan, or ESPP, and potential common shares issued upon the conversion of Convertible Notes of the Company, due March 2029, or the 2029 Convertible Notes. For the year ended December 31, 2023, the Company did not have any options that were excluded in the computation of diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders because the effect would be anti-dilutive. The 2029 Convertible Notes had no impact on the computation of diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders, as the average stock price during the period was less than the conversion price. For the year ended December 31, 2022, options to purchase 704,483 shares of stock with a weighted-average exercise price of $34.79 per share were excluded from the computation of diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders because their effect would be anti-dilutive. For the year ended December 31, 2021, options to purchase 1,906,029 shares of stock with a weighted-average exercise price of $20.82 per share and the reallocation of net income attributable to non-controlling interest were excluded from the computation of diluted net income per common share attributable to Amphastar Pharmaceuticals, Inc. stockholders because their effect would be anti-dilutive. The following table provides the calculation of basic and diluted net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders for each of the periods presented: Year Ended December 31, 2023 2022 2021 (in thousands, except per share data) Basic and dilutive numerator: Net income attributable to Amphastar Pharmaceuticals, Inc. stockholders $ 137,545 $ 91,386 $ 62,116 Denominator: Weighted-average shares outstanding — basic 48,265 48,551 47,777 Net effect of dilutive securities: Incremental shares from equity awards 4,736 3,876 2,007 Weighted-average shares outstanding — diluted 53,001 52,427 49,784 Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — basic $ 2.85 $ 1.88 $ 1.30 Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — diluted $ 2.60 $ 1.74 $ 1.25

Segment Reporting

Segment Reporting	12 Months Ended
Segment Reporting	Dec. 31, 2023
Segment Reporting
Segment Reporting	Note 7. Segment Reporting The Company’s business is the development, manufacture, and marketing of pharmaceutical products. The Company has identified two reporting segments that each report to the Chief Operating Decision Maker, or CODM, as defined in ASC 280, Segment Reporting ● Finished pharmaceutical products ● APIs The finished pharmaceutical products segment manufactures, markets and distributes Primatene MIST ® Other revenues from the sale of BAQSIMI ® Selected financial information by reporting segment is presented below: Year Ended December 31, 2023 2022 2021 (in thousands) Net revenues: Finished pharmaceutical products $ 630,273 $ 486,505 $ 419,570 API 14,122 12,482 18,198 Total net revenues 644,395 498,987 437,768 Gross profit (loss): Finished pharmaceutical products 367,325 256,710 209,715 API (16,204) (7,850) (9,976) Total gross profit 351,121 248,860 199,739 Operating expenses 154,134 141,363 129,852 Income from operations 196,987 107,497 69,887 Non-operating (expenses) income (25,628) 8,543 14,252 Income before income taxes $ 171,359 $ 116,040 $ 84,139 The Company manages its business segments to the gross profit level and manages its operating and other costs on a company-wide basis. The Company does not identify total assets by segment for internal purposes, as the Company’s CODM does not assess performance, make strategic decisions, or allocate resources based on assets. The amount of net revenues in the finished pharmaceutical product segment is presented below: Year Ended December 31, 2023 2022 2021 (in thousands) Finished pharmaceutical products segment net revenues: Glucagon $ 113,684 $ 55,322 $ 47,639 Primatene MIST ® 89,321 84,309 73,113 Epinephrine 81,650 74,204 57,530 Lidocaine 58,162 52,539 44,413 Phytonadione 44,939 49,500 45,498 Enoxaparin 31,533 34,950 35,962 Naloxone 19,004 26,269 27,540 Other finished pharmaceutical products 140,823 109,412 87,875 Total finished pharmaceutical products net revenues 579,116 486,505 419,570 BAQSIMI ® 51,157 — — Total finished pharmaceutical products segment net revenues $ 630,273 $ 486,505 $ 419,570 The amount of depreciation and amortization expense included in cost of revenues by reporting segment is presented below: Year Ended December 31, 2023 2022 2021 (in thousands) Depreciation and amortization expense Finished pharmaceutical products $ 21,794 $ 8,884 $ 6,003 API 3,943 3,713 4,222 Total depreciation and amortization expense $ 25,737 $ 12,597 $ 10,225 Net revenues and carrying values of long-lived assets by geographic regions are as follows: Net Revenue Long-Lived Assets Year Ended December 31, December 31, 2023 2022 2021 2023 2022 (in thousands) United States (1) $ 635,192 $ 486,833 $ 419,869 $ 765,102 $ 136,328 China 4,505 4,697 6,020 91,913 88,647 France 4,698 7,457 11,879 37,647 39,598 Total $ 644,395 $ 498,987 $ 437,768 $ 894,662 $ 264,573 (1) Includes revenue from the sales of BAQSIMI ®

Customer and Supplier Concentra

Customer and Supplier Concentration	12 Months Ended
Customer and Supplier Concentration	Dec. 31, 2023
Customer and Supplier Concentration
Customer and Supplier Concentration	Note 8. Customer and Supplier Concentration Customer Concentrations Three large wholesale drug distributors, Cencora Inc., formally AmerisourceBergen, or Cencora, Cardinal Health, Inc., or Cardinal, and McKesson Corporation, or McKesson, are all distributors of the Company’s products, as well as suppliers of a broad range of health care products. Lilly currently manufactures and sells BAQSIMI ® % of Total Accounts % of Net Receivable Revenue December 31, December 31, Year Ended December 31, 2023 2022 2023 2022 2021 McKesson 26 % 32 % 25 % 22 % 21 % Cencora 16 % 16 % 20 % 23 % 24 % Cardinal Health 13 % 19 % 15 % 17 % 16 % Lilly 20 % — 8 % — — Supplier Concentrations The Company depends on suppliers for raw materials, APIs, and other components that are subject to stringent FDA requirements. Some of these materials may only be available from one or a limited number of sources. Establishing additional or replacement suppliers for these materials may take a substantial period of time, as suppliers must be approved by the FDA. Furthermore, a significant portion of raw materials may only be available from foreign sources. If the Company is unable to secure, on a timely basis, sufficient quantities of the materials it depends on to manufacture and market its products, it could have a materially adverse effect on the Company’s business, financial condition, and results of operations.

Fair Value Measurements

Fair Value Measurements	12 Months Ended
Fair Value Measurements	Dec. 31, 2023
Fair Value Measurements
Fair Value Measurements	Note 9. Fair Value Measurements GAAP defines fair value as the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants in the principal or most advantageous market for the asset or liability at the measurement date (an exit price). These standards also establish a hierarchy that prioritizes observable and unobservable inputs used in measuring fair value of an asset or liability, as described below: ● Level 1 – Inputs to measure fair value are based on quoted prices (unadjusted) in active markets on identical assets or liabilities; ● Level 2 – Inputs to measure fair value are based on the following: a) quoted prices in active markets on similar assets or liabilities, b) quoted prices for identical or similar instruments in inactive markets, or c) observable (other than quoted prices) or collaborated observable market data used in a pricing model from which the fair value is derived; and ● Level 3 – Inputs to measure fair value are unobservable and the assets or liabilities have little, if any, market activity; these inputs reflect the Company’s own assumptions about the assumptions that market participants would use in pricing the assets or liabilities based on best information available in the circumstances. As of December 31, 2023, cash equivalents include money market accounts and corporate and municipal bonds with original maturities of less than three months. Investments consist of certificates of deposit as well as investment-grade corporate, agency and municipal bonds with original maturity dates between three and fifteen months. The certificates of deposit are carried at amortized cost in the Company’s consolidated balance sheets, which approximates their fair value determined based on Level 2 inputs. The corporate, agency and municipal bonds are classified as held-to-maturity and are carried at amortized cost net of allowance for credit losses. The fair value of such bonds is disclosed in Note 10 and was determined based on Level 2 inputs. The restrictions on restricted cash and investments have an immaterial effect on the fair value of these financial assets. The fair values of the Company’s financial assets and liabilities measured on a recurring basis as of December 31, 2023 and 2022, are as follows: Total (Level 1) (Level 2) (Level 3) (in thousands) Cash equivalents $ 116,441 $ 116,441 $ — $ — Restricted cash 235 235 — — Short-term investments 37,142 — 37,142 — Restricted short-term investments 2,200 — 2,200 — Interest rate swaps related to variable rate loans (5,243) — (5,243) — Total assets and liabilities measured at fair value as of December 31, 2023 $ 150,775 $ 116,676 $ 34,099 $ — Total (Level 1) (Level 2) (Level 3) Assets: (in thousands) Cash equivalents $ 130,199 $ 130,199 $ — $ — Restricted cash 235 235 — — Short-term investments 4,600 — 4,600 — Restricted short-term investments 2,200 — 2,200 — Interest rate swaps related to variable rate loans 6,048 — 6,048 — Total assets measured at fair value as of December 31, 2022 $ 143,282 $ 130,434 $ 12,848 $ — The Company does not hold any Level 3 instruments that are measured at fair value on a recurring basis. Nonfinancial assets and liabilities are not measured at fair value on a recurring basis but are subject to fair value adjustments in certain circumstances. These items primarily include investments in unconsolidated affiliates, long-lived assets, goodwill, and intangible assets for which the fair value is determined as part of an impairment test. As of December 31, 2023 and 2022, there were no significant adjustments to fair value for nonfinancial assets or liabilities. The Company’s deferred compensation plan assets are valued using the cash surrender value of the life insurance policies and are not included in the table above.

Investments

Investments	12 Months Ended
Investments	Dec. 31, 2023
Investments
Investments	Note 10. Investments The following is a summary of the Company’s investments that are classified as held-to-maturity: Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (in thousands) Corporate and agency bonds (due within 1 year) $ 73,815 $ 7 $ (21) $ 73,801 Corporate bonds (due within 1 to 3 years) 14,621 56 (1) 14,676 Municipal bonds (due within 1 year) 1,081 1 — 1,082 Total investments as of December 31, 2023 $ 89,517 $ 64 $ (22) $ 89,559 Corporate and agency bonds (due within 1 year) $ 21,612 $ — $ (60) $ 21,552 Municipal bonds (due within 1 year) 1,903 — (2) 1,901 Total investments as of December 31, 2022 $ 23,515 $ — $ (62) $ 23,453 At each reporting period, the Company evaluates securities for impairment when the fair value of the investment is less than its amortized cost. The Company evaluated the underlying credit quality and credit ratings of the issuers, identifying neither a significant deterioration since purchase nor any other factors that would indicate a material credit loss. The Company measures expected credit losses on held-to-maturity investments on a collective basis. All the Company’s held-to-maturity investments were considered to be one pool. The estimate for credit losses considers historical loss information that is adjusted for current conditions and reasonable and supportable forecasts. Expected credit losses on held-to-maturity investments were not material to the consolidated financial statements. Investment in unconsolidated affiliate The Company accounts for its share of the earnings or losses of its unconsolidated affiliate Hanxin with a reporting lag of three months, as the financial statements of Hanxin are not completed on a basis that is sufficient for the Company to apply the equity method on a current basis. The Company’s share of Hanxin’s losses for the years ended December 31, 2023, 2022 and 2021 was $2.0 million, $1.2 million and $0.2 million, respectively, which was recorded in “equity in losses of unconsolidated affiliate” on the accompanying consolidated statement of operations.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
Goodwill and Intangible Assets	Dec. 31, 2023
Goodwill and Intangible Assets
Goodwill and Intangible Assets	Note 11. Goodwill and Intangible Assets The table below shows the weighted-average life, original cost, accumulated amortization, and net book value by major intangible asset classification: Weighted-Average Accumulated Life (Years) Original Cost Amortization Net Book Value (in thousands) Definite-lived intangible assets BAQSIMI ® (1) 24 $ 591,338 $ 12,319 $ 579,019 IMS (UK) international product rights (2) 10 8,462 8,462 — Patents 12 486 376 110 Land-use rights 39 2,540 815 1,725 Subtotal 23 602,826 21,972 580,854 Indefinite-lived intangible assets Trademark * 29,225 — 29,225 Goodwill - Finished pharmaceutical products * 3,216 — 3,216 Subtotal * 32,441 — 32,441 As of December 31, 2023 * $ 635,267 $ 21,972 $ 613,295 Weighted-Average Accumulated Life (Years) Original Cost Amortization Net Book Value (in thousands) Definite-lived intangible assets IMS (UK) international product rights (2) 10 $ 8,462 $ 5,430 $ 3,032 Patents 12 486 362 124 Land-use rights 39 2,540 749 1,791 Subtotal 11 11,488 6,541 4,947 Indefinite-lived intangible assets Trademark * 29,225 — 29,225 Goodwill - Finished pharmaceutical products * 3,126 — 3,126 Subtotal * 32,351 — 32,351 As of December 31, 2022 * $ 43,839 $ 6,541 $ 37,298 * Intangible assets with indefinite lives have an indeterminable average life. (1) See Note 4. (2) In June 2023, the Company recorded an impairment related to its IMS (UK) international product rights in the amount of $2.7 million. The Company recorded the impairment in the cost of revenue in its consolidated statement of operations for the year ended December 31, 2023 Goodwill The changes in the carrying amounts of goodwill are as follows: December 31, 2023 2022 (in thousands) Beginning balance $ 3,126 $ 3,313 Currency translation 90 (187) Ending balance $ 3,216 $ 3,126 Primatene ® Trademark In January 2009, the Company acquired the exclusive rights to the trademark, domain name, website and domestic marketing, distribution and selling rights related to Primatene MIST ® The trademark was determined to have an indefinite life. In determining its indefinite life, the Company considered the following: the expected use of the intangible; the longevity of the brand; the legal, regulatory and contractual provisions that affect their maximum useful life; the Company’s ability to renew or extend the asset’s legal or contractual life without substantial costs; effects of the regulatory environment; expected changes in distribution channels; maintenance expenditures required to obtain the expected future cash flows from the asset; and considerations for obsolescence, demand, competition and other economic factors. BAQSIMI ® Product Rights As discussed in Note 4, in June 2023, the Company acquired the BAQSIMI ® ® ® . ® Amortization Included in cost of revenues for the years ended December 31, 2023, 2022 and 2021 is product rights amortization expense of $15.5 million, $0.9 million, and $1.0 million, respectively. As of December 31, 2023, the expected amortization expense for all amortizable intangible assets during the next five fiscal years ended December 31 and thereafter is as follows: (in thousands) 2024 $ 24,718 2025 24,718 2026 24,718 2027 24,718 2028 24,718 Thereafter 457,264 Total amortizable intangible assets 580,854 Indefinite-lived intangibles 32,441 Total intangibles (net of accumulated amortization) $ 613,295

Inventories

Inventories	12 Months Ended
Inventories	Dec. 31, 2023
Inventories
Inventories	Note 12. Inventories Inventories consist of the following: December 31, 2023 2022 (in thousands) Raw materials and supplies $ 50,082 $ 47,607 Work in process 30,822 37,090 Finished goods 24,929 18,887 Total inventories $ 105,833 $ 103,584 Charges of $18.8 million, $17.2 million, and $24.6 million were included in the cost of revenues in the Company’s consolidated statements of operations for the years ended December 31, 2023, 2022, and 2021, respectively, to adjust the Company’s inventory and related firm purchase commitments to their net realizable value. For the year ended December 31, 2023, these charges included $9.1 million in the cost of revenues to adjust the Company’s enoxaparin inventory and related firm purchase commitments to their net realizable value. Additionally, as a result of amending the MannKind RHI Supply Agreement in December 2023, the Company booked a $3.6 million adjustment to reduce RHI inventory to its net realizable value. For the year ended December 31, 2022, the charge included $14.9 million in the cost of revenues to adjust the Company’s enoxaparin inventory and related firm purchase commitments to their net realizable value. For the year ended December 31, 2021, the charge included $20.7 million as a result of an increase in the price of heparin as well as a decrease in the forecasted average selling price of enoxaparin. Losses on firm purchase commitments related to raw materials on order as of December 31, 2023 and 2022 were $1.0 million and $2.7 million, respectively, which are recorded in cost of revenues in the Company’s consolidated statement of operations.

Property, Plant, and Equipment

Property, Plant, and Equipment	12 Months Ended
Property, Plant, and Equipment	Dec. 31, 2023
Property, Plant, and Equipment.
Property, Plant, and Equipment	Note 13. Property, Plant, and Equipment Property, plant, and equipment consist of the following: December 31, 2023 2022 (in thousands) Buildings $ 168,771 $ 130,726 Leasehold improvements 41,686 31,535 Land 7,484 7,451 Machinery and equipment 259,484 208,068 Furniture, fixtures, and automobiles 31,943 29,674 Construction in progress 18,676 50,842 Total property, plant, and equipment 528,044 458,296 Less accumulated depreciation (245,298) (220,030) Total property, plant, and equipment, net $ 282,746 $ 238,266 The Company incurred depreciation expense of $25.2 million, $23.8 million, and $22.2 million for the years ended December 31, 2023, 2022, and 2021, respectively. Interest expense capitalized was approximately $2.0 million, $1.4 million, and $1.4 million, for the years ended December 31, 2023, 2022, and 2021, respectively.

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	12 Months Ended
Accounts Payable and Accrued Liabilities	Dec. 31, 2023
Accounts Payable and Accrued Liabilities.
Accounts Payable and Accrued Liabilities	Note 14. Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities consisted of the following: December 31, 2023 2022 (in thousands) Accrued customer fees and rebates $ 16,702 $ 14,198 Accrued payroll and related benefits 25,203 22,847 Accrued product returns, current portion 12,263 14,867 Accrued loss on firm purchase commitments 918 2,686 Other accrued liabilities 12,842 9,143 Total accrued liabilities 67,928 63,741 Accounts payable 25,438 20,501 Total accounts payable and accrued liabilities $ 93,366 $ 84,242

Debt

Debt	12 Months Ended
Debt	Dec. 31, 2023
Debt
Debt	Note 15. Debt Debt consists of the following: December 31, 2023 2022 (in thousands) Convertible Debt 2029 Convertible Notes $ 345,000 $ — Term Loan Wells Fargo Term Loan due June 2028 250,000 — Capital One N.A. Term Loan paid off June 2023 — 68,250 Mortgage Loans Mortgage payable with East West Bank due June 2027 8,016 8,188 Other Loans and Payment Obligations French government loans due December 2026 158 204 Line of Credit Facilities Line of credit facility with China Merchant Bank due October 2026 — — Wells Fargo Revolving line of credit facility due June 2028 — — Capital One N.A. Revolving line of credit facility closed in June 2023 — — Equipment under Finance Leases 616 790 Total debt 603,790 77,432 Less current portion of long-term debt 436 3,046 Less: Loan issuance costs 13,775 1,547 Long-term debt, net of current portion and unamortized debt issuance costs $ 589,579 $ 72,839 Credit Agreement 2029 Convertible Notes In September 2023, the Company issued the 2029 Convertible Notes, in the aggregate principal amount of $345.0 million in a private offering pursuant to Section 4(a)(2) and Rule 144A under the Securities Act of 1933, as amended. The Company used portions of the net proceeds from the 2029 Convertible Notes to (i) repay approximately $200.0 million of the Company’s borrowings under the Wells Fargo Term Loan and (ii) repurchase $50.0 million of the Company’s common stock. In connection with the issuance of the 2029 Convertible Notes, the Company incurred approximately $10.8 million of debt issuance costs, which primarily consisted of underwriting, legal and other professional fees. Unamortized debt issuance costs related to the 2029 Convertible Notes were $10.3 million as of December 31, 2023. The fair value of the 2029 convertible notes was approximately $418.8 million as of December 31, 2023 based on level 2 inputs. The 2029 Convertible Notes are general senior, unsecured obligations and bear an interest rate of 2.0% per year. The 2029 Convertible Notes were issued pursuant to an indenture, dated September 15, 2023, or the Indenture, between the Company and U.S. Bank Trust Company, National Association, as trustee. The 2029 Convertible Notes will rank senior in right of payment to all of the Company’s indebtedness that is expressly subordinated in right of payment to the 2029 Convertible Notes; equal in right of payment to all of the Company’s unsecured indebtedness that is not so subordinated; effectively junior to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness, including any amount outstanding under the Company’s credit facilities; and structurally junior to all indebtedness and other liabilities of the Company’s current or future subsidiaries, including trade payables. Interest will be payable semi-annually in arrears on March 15 and September 15 of each year, beginning on March 15, 2024. The 2029 Convertible Notes may bear additional interest under specified circumstances relating to the Company’s failure to comply with its reporting obligations under the Indenture or if the 2029 Convertible Notes are not freely tradeable as required by the Indenture. The 2029 Convertible Notes will mature on March 15, 2029, unless earlier converted, repurchased or redeemed. Conversions of the 2029 Convertible Notes will be settled in cash up to the aggregate principal amount of the 2029 Convertible Notes to be converted, and cash, shares of common stock or a combination of cash and shares of common stock, at the Company’s election, with respect to the remainder, if any, of the Company’s conversion obligation in excess of the aggregate principal amount. Holders may convert their 2029 Convertible Notes at their option prior to the close of business on the business day immediately preceding December 15, 2028, in multiples of $1,000 principal amount, only under the following circumstances; (i) during any calendar quarter commencing after the calendar quarter ending on December 31, 2023 (and only during such calendar quarter), if the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on and including, the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price for the 2029 Convertible Notes on each applicable trading day, (ii) during the five business day period after any five consecutive trading day period in which the trading price, as defined in the Indenture, per $1,000 principal amount of the 2029 Convertible Notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of the Company’s common stock and the conversion rate on each such trading day, (iii) if the Company calls the 2029 Convertible Notes for redemption, at any time prior to the close of business on the second scheduled trading day immediately preceding the redemption date, and (iv) upon the occurrence of specified corporate events defined in the Indenture. On or after December 15, 2028, until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert all or any portion of their 2029 Convertible Notes, in multiples of $1,000 principal amount, at the option of the holder regardless of the foregoing circumstances. The Company may redeem the 2029 Convertible Notes, at its option, in whole or in part (subject to certain limitations), on or after September 20, 2026 and prior to the 41 st The initial conversion rate is 15.8821 shares of the Company’s common stock per $1,000 principal amount of the 2029 Convertible Notes, which represents an initial conversion price of approximately $62.96 per share of common stock. The initial conversion price of $62.96 represents a premium of approximately 35.0% over the last reported sale price of the Company’s common stock on Nasdaq Global Select Market on September 12, 2023. The conversion rate is subject to adjustment under certain circumstances in accordance with the terms of the Indenture. If a fundamental change, as defined in the Indenture, occurs at any time prior to the maturity date, then, subject to certain conditions, holders of the 2029 Convertible Notes may require the Company to repurchase for cash all or any portion of their 2029 Convertible Notes at a repurchase price equal to 100% of the principal amount of the 2029 Convertible Notes to be repurchased, plus any accrued and unpaid interest. In addition, following certain specified corporate events or if the Company issues a notice of redemption, the Company will, under certain circumstances, increase the conversion rate for holders who convert their 2029 Convertible Notes in connection with such corporate event or during a redemption period. Syndicated Credit Agreement with Wells Fargo Bank, National Association - Due June 2028 In June 2023, in connection with the BAQSIMI ® ® The Wells Fargo Term Loan requires principal payments of $12.5 million for the first year, which increases to $25.0 million during the second year, and $37.5 million during the third, fourth and fifth years, with the remaining balance due at maturity. The loan is secured by substantially all of the Company’s and certain of its subsidiaries’ assets, subject to certain exceptions and limitations. In the third quarter of 2023, the Company repaid approximately $200.0 million of the borrowings under the Wells Fargo term Loan with the proceeds from the 2029 Convertible Notes, thereby satisfying all of the current and future loan amortization payments required by the Wells Fargo Term Loan until maturity. In the fourth quarter of 2023, the Company made a principal payment of $50.0 million, reducing the balance to $250.0 million. The Credit Agreement also provides for a $200.0 million Revolving Credit Facility and bears the same interest rate as the Wells Fargo Term Loan. In conjunction with the Credit Agreement, the Company entered into an interest rate swap agreement with Wells Fargo, with a notional amount of $250.0 million to exchange the variable rate on the Wells Fargo Term Loan for a fixed rate of 4.04%. The interest swap agreement had a fair value of $5.4 million liability as of December 31, 2023. For lenders that were part of the previous credit agreement with Capital One N.A. as well as the new Credit Agreement, the transaction was accounted for as a modification under ASC 470-50, Debt Modifications and Extinguishments The Company incurred approximately $14.3 million in issuance costs in connection with the Credit Agreement, of which $3.0 million represented debt modification costs and were charged to interest expense in the Company’s consolidated statement of operations for year ended December 31, 2023. Debt issuance costs associated with the Credit Agreement (other than its Revolving Credit Facility component) are presented as a reduction to the carrying value of the related debt, while debt issuance costs associated with the Revolving Credit Facility are capitalized within other long-term assets on the consolidated balance sheets. Unamortized debt issuance costs related to the Credit Agreement as of December 31, 2023 were $7.8 million which are being amortized over the term of the Credit Agreement using the effective interest rate method. As a result of the $250.0 million repayment of the principal balance of the Wells Fargo Term Loan, approximately $3.8 million of unamortized debt issuance costs were written off during the year ended December 31, 2023. Syndicated Credit Agreement with Capital One N.A. – Paid off June 2023 In August 2021, the Company entered into a $140.0 million credit agreement with Capital One N.A. acting as a lender and as agent for other lenders. Under the terms of the credit agreement, the Company borrowed $70.0 million in the form of a term loan, or the Capital One N.A. Term Loan. Proceeds from the loan were used to pay down certain of the Company’s outstanding loans and revolving lines of credit with Cathay Bank and East West Bank. The interest rate on the Capital One N.A. Term Loan was based on a variable interest rate, plus an applicable margin rate ranging between 0.5% and 2.5%, determined based on the Company’s net leverage ratio as defined by the terms of the agreement. In June 2023, the Company repaid all amounts outstanding under the Capital One N.A. Term Loan. Mortgage Loans Mortgage Payable with East West Bank — Due June 2027 In May 2017, the Company entered into a mortgage term loan with East West Bank in the principal amount of $9.0 million, which matures in June 2027. The loan is payable in monthly installments with a final balloon payment of $7.4 million plus interest. The loan is secured by one of the buildings at the Company’s Rancho Cucamonga, California, headquarters complex and two buildings at the Company’s Chino, California, facility. The loan bears a variable interest rate at the one-month SOFR rate plus 2.6%. The Company entered into a fixed interest rate swap contract on this loan to exchange the variable interest rate for a fixed interest rate of 4.79% until June 2024. Line of Credit Facilities Line of Credit Facility with China Merchant Bank – Due October 2026 In March 2020, the Company entered into a credit agreement with China Merchant Bank. The credit agreement allows the Company to borrow up to $14.6 million secured by buildings and land use rights held by ANP. The interest rate and other terms will be determined at the time of the borrowing, depending on the type of loan requested. The credit period is for 36 months and expired in March 2023. In October 2023, the Company renewed the credit agreement with China Merchant Bank, and allows the Company to borrow up to $4.1 million. The credit period is for 36 months and expires in October 2026. Interest Rate Swap Contracts As of December 31, 2023, the fair value of the loans listed above approximated their carrying amount based on Level 2 inputs. For the mortgage loan with East West Bank, as well as the Wells Fargo Term Loan, the Company has entered into fixed interest rate swap contracts to exchange the variable interest rates for fixed interest rates. The interest rate swap contracts are recorded at fair value in the other assets line in the consolidated balance sheets. Changes in the fair values of interest rate swaps were $5.9 million and $5.5 million for the years ended December 31, 2023 and 2022, respectively. Covenants At December 31, 2023 and 2022, the Company was in compliance with all of its debt covenants. Long-Term Debt Maturities As of December 31, 2023, the principal amounts of long-term debt maturities during each of the next five fiscal years ending December 31 are as follows: Long-term Debt (in thousands) 2024 $ 234 2025 245 2026 254 2027 7,441 2028 250,000 Thereafter 345,000 $ 603,174

Income Taxes

Income Taxes	12 Months Ended
Income Taxes	Dec. 31, 2023
Income Taxes
Income Taxes	Note 16. Income Taxes The Company’s income before income taxes generated from its operations were: Year Ended December 31, 2023 2022 2021 (in thousands) Income before income taxes: United States $ 181,922 $ 127,204 $ 86,236 Foreign (10,563) (11,164) (2,097) Total income before income taxes $ 171,359 $ 116,040 $ 84,139 The Company’s provision for income taxes consisted of the following: Year Ended December 31, 2023 2022 2021 (in thousands) Current provision: Federal $ 42,689 $ 37,626 $ 14,088 State 1,912 732 1,182 Foreign 1,089 998 1,676 Total current provision 45,690 39,356 16,946 Deferred provision (benefit): Federal (13,134) (16,119) 2,657 State 1,537 816 110 Foreign (2,260) (576) 917 Total deferred provision (13,857) (15,879) 3,684 Total provision for income taxes $ 31,833 $ 23,477 $ 20,630 For tax years beginning after December 31, 2021, certain research and development costs are required to be capitalized and amortized over a five or fifteen-year period under the Tax Cuts and Jobs Act of 2017. The Company has reviewed and incorporated this change, which increases the current U.S. federal and state tax expense and cash taxes to be paid for the tax year ending December 31, 2023. A reconciliation of the statutory federal income tax rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2023 2022 2021 Statutory federal income tax 21.0 % 21.0 % 21.0 % State tax expense, net of federal tax benefit 1.6 1.1 1.2 Foreign tax rate differences (0.1) (0.3) (2.0) Foreign valuation allowance 0.1 2.6 5.5 Research and development credits (4.2) (3.1) (3.2) Share-based compensation (3.2) (3.5) (0.2) Executive compensation 2.4 2.3 2.3 Employee-related expenses — 0.2 0.1 Intercompany transfer of assets other than inventory 0.6 — — Other 0.4 (0.1) (0.2) Effective tax rate 18.6 % 20.2 % 24.5 % The Company’s effective tax rate for 2023 decreased in comparison to 2022 primarily due to differences in pre-tax income positions, including jurisdictions where the Company maintains valuation allowance reserves against its deferred tax assets, and additional research and development credit benefit. Deferred Tax Assets and Liabilities Deferred income taxes reflect the tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes, tax credit carryforwards, and the tax effects of net operating loss carryforwards. The significant components of the Company’s deferred tax assets and liabilities are as follows: December 31, 2023 2022 (in thousands) Deferred tax assets: Research and development credits $ 12,759 $ 15,418 Net operating loss carryforward 20,156 20,019 Inventory capitalization and reserve 12,381 9,598 Share-based compensation 5,464 5,208 Operating leases 8,360 6,684 Accrued expenses 5,970 4,956 Accrued chargebacks 5,441 5,125 Product return allowance 4,927 5,464 Intangibles 2,124 2,124 Research and development capitalization 34,036 17,988 Total deferred tax assets 111,618 92,584 Deferred tax liabilities: Depreciation/amortization 21,630 13,272 Intangibles 4,367 8,564 Operating leases 8,037 6,398 Federal impact of state deferred taxes 3,577 3,800 Other 260 2,467 Total deferred tax liabilities 37,871 34,501 Valuation allowance (20,495) (19,700) Net deferred tax assets $ 53,252 $ 38,383 Net Operating Loss Carryforwards and Tax Credits At December 31, 2023, the Company had no material U.S. federal or state net operating loss carryforwards, or NOL carryforwards. The Company had France and United Kingdom foreign NOL carryforwards of approximately $76.2 million and $2.8 million, respectively. The France and United Kingdom NOL carryforwards can be used annually with certain limitations and have an indefinite carryforward. At December 31, 2023, the Company had California research and development tax credit carryforwards of approximately $20.2 million. The California research and development tax credit has an indefinite carryforward period. Valuation Allowance In assessing the need for a valuation allowance, management considers whether it is more likely than not that some portion or all of the deferred income tax assets will be realized. Ultimately, realization depends on the existence of future taxable income. Management considers sources of taxable income such as income in prior carryback periods, future reversal of existing deferred taxable temporary differences, tax-planning strategies, and projected future taxable income. During the year ended December 31, 2023, the Company determined its U.K. subsidiaries, AUK and IMS UK, more likely than not would not realize the benefits of their deferred tax assets. Therefore, the Company recorded a valuation allowance expense of an immaterial amount and will discontinue recognizing income tax benefits until sufficient taxable income is generated to realize their deferred tax assets. The Company continues to record a full valuation allowance on AFP’s net deferred income tax assets and will continue to do so until AFP generates sufficient taxable income to realize its deferred income tax assets. As of December 31, 2023 and 2022, the Company had a full valuation allowance against the net deferred tax assets of AFP, which totaled $19.0 million and $18.9 million, respectively. The Company records a valuation allowance on net deferred income tax assets in states where it files separately and will continue to do so until sufficient taxable income is generated to realize these state deferred income tax assets. Undistributed Earnings from Foreign Operations As of December 31, 2023 and 2022, deferred income taxes have not been provided for any undistributed earnings from foreign operations. The foreign subsidiaries have significant accumulated losses, and as such there are no earnings in which to provide taxes. It is the Company’s plan not to repatriate future foreign earnings to the U.S. and indefinitely reinvest such earnings in the foreign jurisdiction. Uncertain Income Tax Positions A reconciliation of the beginning and ending balances of unrecognized tax benefits is as follows: December 31, 2023 2022 2021 (in thousands) Balance at the beginning of the year $ 12,895 $ 11,796 $ 10,053 Deductions based on tax positions related to prior year — (41) — Additions based on tax positions related to the current year 2,074 1,643 1,754 Deductions based on statute of limitations (2,476) (503) (11) Balance at the end of the year $ 12,493 $ 12,895 $ 11,796 Included in the balance of unrecognized tax benefits as of December 31, 2023 and 2022, was $11.7 million and $12.2 million, respectively that represents the portion that would impact the effective income tax rate if recognized. The Company recognizes interest and penalties related to unrecognized tax benefits in its income tax provision. For the years ended December 31, 2023, 2022 and 2021, the Company accrued interest of approximately $1.0 million, $0.8 million and $0.5 million, respectively, related to its uncertain tax positions. The Company and/or one or more of its subsidiaries files income tax returns in the U.S. federal jurisdiction and various U.S. states and foreign jurisdictions. As of December 31, 2023, the Company is under examination in California for the 2019-2021 tax years, but does not have a tax examination in progress for federal, Massachusetts, other states, or foreign jurisdictions. The Company is subject to income tax audit by tax authorities for tax years 2020 to 2022 for federal, 2019 to 2022 for states, and 2013 to 2022 for foreign.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
Stockholders' Equity	Dec. 31, 2023
Stockholders' Equity
Stockholders' Equity	Note 17. Stockholders' Equity Equity Plans As of December 31, 2023, the Company has two equity plans: the Amended and Restated 2015 Equity Incentive Plan, or 2015 Plan, and the 2014 Employee Stock Purchase Plan or ESPP. Prior to the adoption of these plans, the Company granted options pursuant to the Amended and Restated 2005 Equity Incentive Award Plan. Upon termination of the predecessor plans, the shares available for grant at the time of termination, and shares subsequently returned to the plans upon forfeiture or option termination, were transferred to the successor plan in effect at the time of share return. The Company issues new shares of common stock upon exercise of stock options, vesting of restricted stock units, or RSU, and settlement of ESPP, with the exception of the awards granted to employees at AFP, which are settled through re-issuance of the Company’s treasury shares. Amended and Restated 2015 Equity Incentive Plan In March 2015, the Board of Directors adopted the Company’s 2015 Equity Incentive Plan, or the 2015 Plan, which was approved by the Company’s stockholders in May 2015 and is set to expire in March 2025. The 2015 Plan is designed to meet the needs of a publicly traded company, including the requirements for granting “performance based compensation” under Section 162(m) of the Internal Revenue Code. The 2015 Plan provides for the grant of incentive stock options, nonstatutory stock options, restricted stock, restricted stock units, stock appreciation rights, performance units, performance shares, and other stock or cash awards to employees of the Company and its subsidiaries, members of the Board of Directors and consultants. In November 2020, the Board of Directors approved the Amendment and Restated 2015 Equity Incentive Plan to provide that at least 95% of the shares awarded under the plan will be subject to a minimum vesting requirement of at least one year . The Company initially reserved 5,000,000 shares of common stock for issuance under the 2015 Plan. This number will be increased by the number of shares available for issuance under the Company’s prior equity incentive plans or arrangements that are not subject to options or other awards, plus the number of shares of common stock related to options or other awards granted under the Company’s prior equity incentive plans or arrangements that are repurchased, forfeited, expired, or cancelled on or after the effective date of the 2015 Plan. The 2015 Plan also contains an “evergreen provision” that allows for an annual increase in the number of shares available for issuance on January 1 of each year during the 10 year term of the 2015 Plan, beginning January 1, 2016. The annual increase in the number of shares shall be the lesser of (i) 3,000,000 shares, (ii) two and one-half percent ( 2.5% ) of the outstanding shares on the last day of the immediately preceding fiscal year, or (iii) such number of shares as determined by the Board of Directors. As of the effective date of the 2015 Plan, there were 5,300,296 shares available for grant under the 2015 Plan. As of December 31, 2023, the Company reserved an aggregate of 6,777,943 shares of common stock for future issuance under the Amended and Restated 2015 Equity Incentive Plan, or the 2015 Plan, including 1,201,722 shares, which were reserved in January 2024 pursuant to the evergreen provision in the 2015 Plan. Amended and Restated 2005 Equity Incentive Award Plan The Amended and Restated 2005 Equity Incentive Award Plan, or 2005 Plan, provided for the grant of incentive stock options, or ISOs, nonqualified stock options, or NQSOs, restricted stock awards, restricted stock unit awards, stock appreciation rights, or SARs, dividend equivalents and stock payments to the Company’s employees, members of the Board of Directors and consultants. Stock options under the 2005 Plan were granted with a term of up to ten years and at prices no less than the fair market value of the Company’s common stock on the date of grant. To date, stock options granted to existing employees generally vest over three to five years and stock options granted to new employees vest over four years . Stock options granted to Board of Directors and consultants generally vested over one year . 2014 Employee Stock Purchase Plan In June 2014, the Company adopted the ESPP in connection with its initial public offering. A total of 2,000,000 shares of common stock are reserved for issuance under this plan. The Company’s ESPP permits eligible employees to purchase common stock at a discount through payroll deductions during defined offering periods. Under the ESPP, the Company may specify offerings with durations of not more than 27 months, and may specify shorter purchase periods within each offering. Each offering will have one or more purchase dates on which shares of its common stock will be purchased for employees participating in the offering. An offering may be terminated under certain circumstances. The price at which the stock is purchased is equal to 85% of the lower of the fair market value of the common stock at the beginning of an offering period or on the date of purchase. As of December 31, 2023, the Company has issued 1,192,134 shares of common stock under the ESPP and 807,866 shares of its common stock remains available for issuance under the ESPP. For the years ended December 31, 2023, 2022, and 2021, the Company recorded ESPP expense of $1.1 million, $0.9 million, and $0.7 million, respectively. Share Buyback Program As of December 31, 2023, the Company’s Board of Directors have authorized a total of $285.0 million in the share buyback program. The primary goal of the program is to offset dilution created by the Company’s equity compensation programs. The Company’s share buyback program is expected to continue for an indefinite period of time. Purchases are made through open market and private block transactions pursuant to Rule 10b5-1 plans, privately negotiated transactions or other means as determined by the Company’s management and in accordance with the requirements of the SEC and applicable laws. The timing and actual number of treasury share purchases will depend on a variety of factors including price, corporate and regulatory requirements, and other conditions. These treasury share purchases are accounted for under the cost method and are included as a component of treasury stock in the Company’s consolidated balance sheets. Pursuant to the Company’s existing share buyback program, the Company purchased 1,338,757 shares, 1,335,528 shares, and 1,477,305 shares of its common stock during the years ended December 31, 2023, 2022 and 2021, for total consideration of $58.1 million, $39.9 million, and $28.9 million, respectively. Share-Based Award Activity and Balances (excluding the ANP Equity Plan) The Company accounts for share-based compensation payments in accordance with ASC 718, which requires measurement and recognition of compensation expense at fair value for all share-based payment awards made to employees and directors. Under these standards, the fair value of option awards and the option components of the ESPP awards are estimated at the grant date using the Black-Scholes option-pricing model. The fair value of RSUs is estimated at the grant date using the Company’s common share price. Compensation cost for all share-based payments granted with service-based graded vesting schedules is recognized using the straight-line method over the requisite service period. Options issued under the Company’s 2015 Plan and 2005 Plan are granted at exercise prices equal to or greater than the fair value of the underlying common shares on the date of grant and vest based on continuous service. There have been no awards with performance conditions and no awards with market conditions. The options have a contractual term of five three five The significant assumptions used in the Black-Scholes option-pricing are as follows: ● Determination of Fair Value of the Underlying Common Stock. For options and ESPP awards granted, the fair value for its underlying common stock is determined using the closing price on the date of grant as reported on the Nasdaq Global Select Market, or Nasdaq, with consideration of whether there is material nonpublic information that could impact that estimated fair value when it is released. ● Expected Volatility. The Company estimates its volatility based on the historical volatility of its stock price since IPO. ● Expected Term. The expected term represents the period of time in which the options granted are expected to be outstanding. The Company estimates the expected term of options with consideration of vesting date, contractual term, and historical experience for exercise and post-vesting employment or contractual termination behavior after its common stock has been publicly traded. The expected term of “plain vanilla” options is estimated (using the simplified method as outlined in SAB Topic 14 due to a lack of sufficient historical exercise data) based on the midpoint between the vesting date and the end of the contractual term under the simplified method permitted by the SEC implementation guidance. ● Risk- Free Rate. The risk-free interest rate is selected based upon the implied yields in effect at the time of the option grant on U.S. Treasury zero-coupon issues with a term approximately equal to the expected life of the option being valued. ● Dividends. The Company does not anticipate paying cash dividends in the foreseeable future. Consequently, the Company uses an expected dividend yield rate of zero. The Company estimates forfeitures at the time of grant and revises those estimates in subsequent periods if actual experience differs from those estimates. For the years ended December 31, 2023, 2022 and 2021, the Company estimated an average overall forfeiture rate of approximately 7%, 7%, and 6%, respectively, based on historical experience. Forfeiture rates are separately estimated for its (1) directors and officers, (2) management personnel and (3) other employees. Share-based compensation is recorded net of expected forfeitures. The Company periodically assesses the forfeiture rate and the amount of expense recognized based on estimated historical forfeitures as compared to actual forfeitures. Changes in estimates are recorded in the period they are identified. Tax benefits resulting from tax deductions in excess of the share-based compensation cost recognized (excess tax benefits) are recorded in the statements of cash flows as financing activities. The weighted-averages for key assumptions used in determining the fair value of options granted are as follows: Year Ended December 31, 2023 2022 2021 Average volatility 41.4 % 41.0 % 42.1 % Average risk-free interest rate 4.1 % 2.3 % 1.2 % Weighted-average expected life in years 6.2 6.1 6.1 Dividend yield rate — % — % — % Stock Options A summary of option activity under all plans for the year ended December 31, 2023, is presented below: Weighted-Average Weighted-Average Remaining Aggregate Exercise Contractual Intrinsic Options Price Term (Years) Value (1) (in thousands) Outstanding as of December 31, 2022 7,929,150 $ 17.66 Options granted 759,820 35.84 Options exercised (920,817) 15.40 Options forfeited (5,312) 30.82 Options expired (543) 16.25 Outstanding as of December 31, 2023 7,762,298 $ 19.70 4.54 $ 327,155 Exercisable as of December 31, 2023 5,685,943 $ 16.55 3.25 $ 257,560 Vested and expected to vest as of December 31, 2023 7,601,023 $ 19.46 4.46 $ 322,203 (1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the estimated fair value of the Company’s stock for those awards that have an exercise price below the estimated fair value at December 31, 2023. During the years ended December 31, 2023, 2022, and 2021, the Company recorded expense of $9.6 million, $8.5 million, and $8.0 million, respectively, related to stock options granted under all plans. Information relating to option grants and exercises is as follows: Year Ended December 31, 2023 2022 2021 (in thousands, except per share data) Weighted-average grant date fair value per share $ 16.76 $ 14.75 $ 7.62 Intrinsic value of options exercised 29,918 21,279 7,906 Cash received from options exercised 14,172 19,202 16,757 Total fair value of the options vested during the period 8,890 8,174 8,177 A summary of the status of the Company’s non-vested options as of December 31, 2023, and changes during the year ended December 31, 2023, are presented below: Weighted-Average Grant Date Options Fair Value Non-vested as of December 31, 2022 2,378,453 $ 9.48 Options granted 759,820 16.76 Options vested (1,056,606) 8.41 Options forfeited (5,312) 13.94 Non-vested as of December 31, 2023 2,076,355 12.68 As of December 31, 2023, there was $17.1 million of total unrecognized compensation cost, net of forfeitures, related to non-vested stock option based compensation arrangements granted under all plans. The cost is expected to be recognized over a weighted-average period of 2.5 years and will be adjusted for future changes in estimated forfeitures. Restricted Stock Units The Company grants restricted stock units, or RSUs, to certain employees and members of the Board of Directors with a vesting period of up to five years. The grantee receives one share of common stock at a specified future date for each RSU awarded. The RSUs may not be sold or otherwise transferred until vested. The RSUs do not have any voting or dividend rights prior to the issuance of underlying common stock. The share-based expense associated with these grants was based on the Company’s common stock fair value at the time of grant and is amortized over the requisite service period, which generally is the vesting period, using the straight-line method. During the years ended December 31, 2023, 2022, and 2021, the Company recorded expenses of $9.5 million, $8.4 million, and $8.1 million, respectively, related to RSU awards granted under all plans. As of December 31, 2023, there was $18.1 million of total unrecognized compensation cost, net of forfeitures, related to non-vested RSU-based compensation arrangements granted under all plans. The cost is expected to be recognized over a weighted-average period of 2.5 years and will be adjusted for future changes in estimated forfeitures. Information relating to RSU grants and deliveries is as follows: Total Fair Market Total RSUs Value of RSUs Issued Issued (1) (in thousands) RSUs outstanding at December 31, 2022 1,007,052 RSUs granted 356,176 $ 12,725 RSUs forfeited (2,368) RSUs vested (2) (440,484) RSUs outstanding at December 31, 2023 920,376 (1) The total FMV is derived from the number of RSUs granted times the current stock price on the date of grant. (2) Of the vested RSUs, 168,067 shares of common stock were surrendered to fulfil tax withholding obligations. The 2018 ANP Equity Incentive Plan In December 2018, ANP’s board of directors approved the 2018 Plan, which was set to expire in December 2023. The 2018 Plan permitted the grant of stock options and other equity awards in ANP shares to ANP employees. During the second quarter of 2021, in connection with the ANP restructuring, the 2018 Plan was terminated. At the time the 2018 Plan was terminated, the number of stock options outstanding under the 2018 Plan was 5,018,880. As part of the termination, ANP cash settled 4,091,080 stock options, of which 1,944,771 stock options were vested and 2,146,309 stock options were unvested, for $0.8 million which approximated the fair value of these awards at the time of the settlement. The cash settlement of these awards was recorded as a reduction in equity. For the remaining 927,800 stock option awards that were outstanding under the 2018 Plan at the time the 2018 Plan was terminated, of which 56,925 stock options were vested and 870,875 were unvested, the Company cancelled these awards and issued replacement awards under the 2015 Plan. The modified awards vest over periods ranging from 1 to 2 years and have a 10-year contractual term. The cancellation and replacement of the awards was accounted for as a modification in accordance with ASC 718. As a result of the modification, the cost to the Company was $2.3 million, of which $1.8 million was recorded as share-based compensation within general and administrative expenses in the consolidated statement of operations for the year ended December 31, 2021, and the remaining $0.5 million which will be recognized over the vesting period of the modified awards. Prior to the termination of the 2018 Plan, for the year ended December 31, 2021, the Company recorded expense of $0.5 million related to stock options issued by ANP under the 2018 Plan. Share-based Compensation Expense The Company recorded share-based compensation expense, which is included in the Company’s consolidated statement of operations as follows: Year Ended December 31, 2023 2022 2021 (in thousands) Cost of revenues $ 4,891 $ 4,179 $ 3,778 Operating expenses: Selling, distribution, and marketing 870 726 596 General and administrative 12,269 11,180 12,622 Research and development 2,212 1,775 1,691 Total share-based compensation $ 20,242 $ 17,860 $ 18,687

Employee Benefits

Employee Benefits	12 Months Ended
Employee Benefits	Dec. 31, 2023
Employee Benefits
Employee Benefits	Note 18. Employee Benefits 401(k) Plan The Company has a defined contribution 401(k) plan, or the Plan, whereby eligible employees voluntarily contribute up to a defined percentage of their annual compensation. The Company matches contributions at a rate of 50% on the first 6% of employee contributions, and pays the administrative costs of the Plan. Total employer contributions for the years ended December 31, 2023, 2022, and 2021 were approximately $2.3 million, $2.2 million, and $2.0 million, respectively. Defined Benefit Pension Plan The Company’s subsidiary, AFP, has an obligation associated with a defined-benefit plan for its eligible employees. This plan provides benefits to the employees from the date of retirement and is based on the employee’s length of time employed by the Company. The calculation is based on a statistical calculation combining a number of factors that include the employee’s age, length of service, and AFP employee turnover rate. The liability under the plan is based on a discount rate of 3.25% and 3.75% as of December 31, 2023 and 2022, respectively. The liability is included in other long-term liabilities in the accompanying consolidated balance sheets. The plan is currently unfunded, and the benefit obligation under the plan was $2.6 million and $2.2 million at December 31, 2023 and 2022, respectively. The Company recorded an immaterial amount of expense under the plan for each of the years ended December 31, 2023, 2022 and 2021. Gain or loss due to change in actuarial valuation of the Company’s defined benefit pension plan is recorded in other comprehensive income (loss). Non-qualified Deferred Compensation Plan In December 2019, the Company established a non-qualified deferred compensation plan. The plan allows certain eligible participants to defer a portion of their cash compensation and provides a matching contribution at the discretion of the Company. The plan obligations are payable upon retirement, termination of employment and/or certain other times in a lump-sum distribution or in installments, as elected by the participant in accordance with the plan. Participants can allocate their deferred compensation amongst various investment options with earnings accruing to the participant. The Company has established a Rabbi Trust to fund the plan obligations and to hold the plan assets. Eligible participants began contributing to the plan in January 2020. The plan assets were valued at approximately $6.8 million and $4.5 million as of December 31, 2023 and 2022, respectively. The plan liabilities were valued at approximately $7.1 million and $4.6 million as of December 31, 2023 and 2022, respectively. The plan assets and liabilities are included in other long-term assets and other long-term liabilities, respectively, on the Company’s consolidated balance sheets.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
Commitments and Contingencies	Dec. 31, 2023
Commitments and Contingencies
Commitments and Contingencies	Note 19. Commitments and Contingencies Lease Liabilities Right-of-Use, or ROU, assets represent the Company’s right to control an underlying asset for the lease term and lease liabilities represent the Company’s obligation to make lease payments arising from the lease. ROU assets and liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. Lease terms are generally based on their initial non-cancelable terms, unless there is a renewal option that is reasonably certain to be exercised. Various factors, including economic incentives, intent, past history, and business needs are considered to determine if a renewal option is reasonably certain to be exercised. As most of its leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the discount rate used to present value the lease payments. The Company has lease agreements with both lease and non-lease components, which are accounted for as a single component for all asset classes. The Company leases real and personal property, in the normal course of business, under various non-cancelable operating leases. The Company, at its option, can renew a substantial portion of its leases, at the market rate, for various renewal periods ranging from one to six years . The components of lease costs were as follows: Year Ended December 31, 2023 2022 2021 (in thousands) Operating lease costs $ 5,267 $ 4,709 $ 4,328 Short-term lease costs 332 300 518 Finance lease costs Amortization of right-of-use assets 189 237 384 Interest on lease liabilities 45 26 26 Total finance lease costs $ 234 $ 263 $ 410 Total lease costs $ 5,833 $ 5,272 $ 5,256 Other information pertaining to leases is as follows: Year Ended December 31, 2023 2022 2021 (in thousands, except lease term and discount rate) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows paid for operating leases $ 5,106 $ 4,329 $ 4,446 Operating cash flows paid for finance leases 40 18 25 Financing cash flows paid for finance leases 154 233 310 Right-of use assets obtained in exchange for lease liabilities Operating leases 10,521 2,166 11,041 Finance leases — 642 110 Weighted-average remaining lease term (years) Operating leases 7.7 8.7 9.5 Finance leases 3.4 4.3 2.4 Weighted-average discount rate Operating leases 5.5 % 4.4 % 4.5 % Finance leases 6.7 % 6.7 % 5.2 % Future minimum rental payments under leases that have initial or remaining non-cancelable lease terms in excess of 12 months as of December 31, 2023, are as follows: Operating Finance Leases Leases Total (in thousands) 2024 $ 5,611 $ 236 $ 5,847 2025 5,536 190 5,726 2026 5,586 158 5,744 2027 5,359 104 5,463 2028 4,605 — 4,605 Thereafter 14,805 — 14,805 Total lease payments $ 41,502 $ 688 $ 42,190 Less: interest 7,875 72 7,947 Total $ 33,627 $ 616 $ 34,243 Purchase Commitments As of December 31, 2023, the Company has entered into commitments to purchase equipment and raw materials for an aggregate amount of approximately $93.3 million.

Related-Party Transactions

Related-Party Transactions	12 Months Ended
Related-Party Transactions	Dec. 31, 2023
Related-Party Transactions
Related-Party Transactions	Note 20. Related-Party Transactions ANP Restructuring and Investment in Hanxin Subsequent to the ANP restructuring discussed in Note 3, which involved various related parties, Hanxin is no longer a wholly-owned subsidiary of the Company and was deconsolidated in the third quarter of 2021. The Company determined that it has significant influence over Hanxin as a result of its 11.5% ownership interest, its seat on Hanxin’s board of directors, and Henry Zhang’s position as an equity holder, general manager, and chairman of the board of directors of Hanxin, given he is the son of Dr. Jack Zhang. Additionally, Dr. Mary Luo and Dr. Jack Zhang, through an affiliated entity, have an ownership interest in Hanxin and as such Hanxin continues to be a related party after the restructuring. Contract manufacturing agreement with Hanxin In April 2022, ANP, entered into a contract manufacturing agreement with Hanxin, whereby Hanxin will develop several active pharmaceutical ingredients and finished products for the Chinese market and will engage ANP to manufacture the products on a cost-plus basis. Hanxin will commit to purchase certain quantities from ANP subject to the terms and conditions set forth in the agreement, including Hanxin filing for and obtaining any required marketing authorizations. During the years ended December 31, 2023 and 2022, the Company recognized $0.1 million and $0.4 million of revenue from manufacturing services provided to Hanxin, respectively. As of December 31, 2023, the Company did not have any receivables from Hanxin. Contract Research Agreement with Hanxin In July 2022, the Company entered into a three-year contract research agreement with Hanxin, a related party, whereby Hanxin will develop Recombinant Human Insulin Research Cell Banks, or RCBs, for the Company and license the RCBs to the Company subject to a fully paid, exclusive, perpetual, transferable, sub-licensable worldwide license. The RCBs will be used by the Company to make Master Cell Banks for one of its product candidates. Per the terms of the agreement with Hanxin, all title to the RCBs developed, prepared and produced by Hanxin in conducting research and development will belong to the Company. The Company will also own any confidential and proprietary information, technology regarding development and manufacturing of the RCBs, which shall include engineering, scientific and practical information and formula, research data, design, and procedures and others to develop and manufacture the RCBs, in use or developed by Hanxin. The total cost of the agreement to the Company shall not exceed approximately $2.2 million, with payments adjusted based on the then current exchange rates. Any additional work or changes to the scope of work requested by the Company will be charged by Hanxin to the Company on a cost-plus basis, plus any applicable taxes. In March 2023, the Company amended the agreement with Hanxin, whereby Hanxin will perform scale-up manufacturing process development using the RCBs for the Company. Per the terms of the amended agreement the Company will own any confidential and proprietary information and technology produced during the scale-up manufacturing, which shall include engineering, scientific and practical information and formula, research data design and procedures and others to develop and manufacture the RCBs. The amendment agreement will remain in full force and effect until July 5, 2025. The total cost of the amended agreement to the Company shall not exceed approximately $0.5 million in additional payments beyond the $2.2 million in payments under the contract research agreement, with payments adjusted based on actual currency exchange rates. Any additional work or changes to the scope of work requested by the Company will be charged by Hanxin to the Company on a cost-plus basis, plus any applicable taxes. During the years ended December 31, 2023 and 2022, the Company paid $1.6 million and $0.6 million, respectively, under this agreement. Supply Agreement with Letop In November 2022, ANP entered in to a supply agreement with Nanjing Letop Biotechnology Co., Ltd., or Letop, which is considered a related-party due to an ownership stake by Henry Zhang. Under the terms of the supply agreement Letop will manufacture and deliver chemical intermediates for ANP on a cost-plus basis. The agreement is effective for three years and the total cost of the agreement shall not exceed approximately $1.5 million, with payments adjusted based on the then current exchange rates. During the years ended December 31, 2023 and 2022, ANP paid $0.7 million and $0.2 million, respectively, under this agreement. As of December 31, 2023, the Company did not have any additional accruals payable to Letop.

Litigation

Litigation	12 Months Ended
Litigation	Dec. 31, 2023
Litigation
Litigation	Note 21. Litigation Amphastar Pharmaceuticals, Inc. v Aventis Pharma, SA In January 2009, the Company filed a qui tam ® On November 13, 2020, the Court issued an Order (“November Order”) awarding Aventis $12.1 million in attorneys’ fees and $0.7 million in costs and expenses. The Company recorded $12.8 million in other income (expenses) in the consolidated statement of operations for the year ended December 31, 2020. On May 3, 2021, the Court issued a further Order based upon supplemental application to the Court seeking fees, expenses, and interest for the period after, and not covered by, the November Order. The Court awarded Aventis an additional $4.4 million bringing the total amount awarded to Aventis to $17.2 million. On June 30, 2021, the Company and Aventis entered into a settlement agreement to settle the attorney fees’ and expenses claim for $14.5 million. The additional $1.7 million was recorded in other income (expenses), in the consolidated statement of operations. The settlement was paid in full in the third quarter of 2021. Hatch-Waxman Litigation Regadenoson (0.4 mg/5 mL, 0.08 mg/mL) Patent Litigation On February 25, 2020, Astellas US LLC, Astellas Pharma US, Inc., and Gilead Sciences, Inc. (collectively, “Astellas-Gilead”) filed a Complaint in the United States District Court for the District of Delaware against IMS for infringement of U.S. Patent Nos. 8,106,183 (the “‘183 patent”), RE47,301 (the “‘301 patent”), and 8,524,883 (the “‘883 patent”) (collectively, “Astellas-Gilead Patents”) with regard to IMS’s ANDA No. 214,252 for approval to manufacture and sell 0.4 mg/5 mL (0.08 mg/mL) intravenous solution of Regadenoson. On January 26, 2022, the Company and Astellas-Gilead reached an agreement to resolve the lawsuit. Under the terms of the agreement, the Company received $5.4 million from Astellas constituting saved litigation expenses. The Company recorded the settlement amount in other income (expenses) in its consolidated statement of operations for the year ended December 31, 2022. Employee Litigations In 2021 the Company settled employee litigations relating to alleged violations of various California labor laws pertaining to wage and hour against the Company. For the year ended December 31, 2021, the Company recorded $1.0 million, related to the settlement of employment litigation, in general and administrative expense in the Company’s consolidated statements of operations. Other Litigation The Company is also subject to various other claims, arbitrations, investigations, and lawsuits from time to time arising in the ordinary course of business. In addition, third parties may, from time to time, assert claims against the Company in the forms of letters and other communications. The Company records a provision for contingent losses when it is both probable that a liability has been incurred and the amount of the loss can be reasonably estimated. In the opinion of management, the ultimate resolution of any such matters is not expected to have a material adverse effect on its financial position, results of operations, or cash flows; however, the results of litigation and claims are inherently unpredictable and the Company’s view of these matters may change in the future. Regardless of the outcome, litigation can have an adverse impact on the Company because of defense and settlement costs, diversion of management resources, and other factors.

Subsequent Events

Subsequent Events	12 Months Ended
Subsequent Events	Dec. 31, 2023
Subsequent Events
Subsequent Events	Note 22. Subsequent Events Syndicated Line of Credit Facility with ICBC Bank – Due June 2033 In January 2024, the Company entered into a credit agreement with ICBC Bank acting as a lender and as agent for other lenders. The credit agreement allows the Company to borrow up to $40.0 million secured by equipment and buildings at ANP. The interest rate and other terms will be determined at the time of the borrowing, depending on the type of loan requested. The credit agreement expires in November 2033.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2023
Summary of Significant Accounting Policies
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of the Company and its subsidiaries, and are prepared in accordance with United States generally accepted accounting principles, or GAAP. Certain prior period amounts have been reclassified within the operating activities of the consolidated statements of cash flows to conform to the current period presentation. All intercompany activity has been eliminated in the preparation of the consolidated financial statements. In the opinion of management, the accompanying consolidated financial statements include all adjustments, which are of a normal recurring nature, necessary to present fairly the consolidated financial position, results of operations, and cash flows of the Company. The Company’s subsidiaries include: (1) International Medication Systems, Limited, or IMS, (2) Armstrong Pharmaceuticals, Inc., or Armstrong, (3) Amphastar Nanjing Pharmaceuticals Inc., or ANP, (4) Amphastar France Pharmaceuticals, S.A.S., or AFP, (5) Amphastar UK Ltd., or AUK, (6) International Medication Systems (UK) Limited, or IMS UK, and (7) Amphastar Medication Co., LLC, or Amphastar Medication.
Investment in Unconsolidated Affiliates	Investment in Unconsolidated Affiliate The Company applies the equity method of accounting for investments when it has significant influence, but not controlling interest in the investee. Judgment regarding the level of influence over each equity method investment includes key factors such as ownership interest, representation on the board of directors, participation in policy-making decisions and material intercompany transactions. The Company’s proportionate share of the earnings or losses resulting from these investments is reported as “Equity in losses of unconsolidated affiliate” in the accompanying consolidated statements of operations. Investments accounted for using the equity method may be reported on a lag of up to three months if financial statements of the investee are not available in sufficient time for the investor to apply the equity method as of the current reporting date. The determination of whether an investee’s results are recorded on a lag is made on an investment-by-investment basis. The carrying value of equity method investments is reported as “Investment in unconsolidated affiliate” in the accompanying consolidated balance sheets. The Company’s equity method investments are reported at cost and adjusted each period for the Company’s share of the investee’s earnings or losses and dividends paid, if any. The Company assesses equity method investments for impairment whenever events or changes in circumstances indicate that the carrying value of an investment may not be recoverable. If the decline in value is considered to be other than temporary, the investment is written down to its estimated fair value, which establishes a new cost basis in the investment. No such impairment was identified for any of the periods presented.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in accordance with GAAP requires management to make estimates and assumptions that affect the amounts reported in the consolidated financial statements and accompanying notes. Actual results could differ from those estimates. The principal accounting estimates include: fair value of acquired assets, determination of allowances for credit losses, fair value of financial instruments, allowance for discounts, provision for chargebacks and rebates, provision for product returns, adjustment of inventory to its net realizable value, impairment of investments, long-lived and intangible assets and goodwill, accrual for workers’ compensation liabilities, litigation reserves, stock price volatility for share-based compensation expense, valuation allowances for deferred tax assets, and liabilities for uncertain income tax positions.
Foreign Currency	Foreign Currency The functional currency of the Company, its domestic subsidiaries, its Chinese subsidiary ANP, and its U.K. subsidiary, AUK, is the U.S. Dollar, or USD. ANP maintains its books of record in Chinese yuan. These books are remeasured into the functional currency of USD using the current or historical exchange rates. The resulting currency remeasurement adjustments and other transactional foreign currency exchange gains and losses are reflected in the Company’s accompanying consolidated statements of operations. The Company’s French subsidiary, AFP, maintains its book of record in euros. AUK’s subsidiary, IMS UK, maintains its book of record in British pounds. These local currencies have been determined to be the subsidiaries’ respective functional currencies. Activities in the statements of operations are translated to USD using average exchange rates during the period. Assets and liabilities are translated at the rate of exchange prevailing on the balance sheet date. Equity is translated at the prevailing rate of exchange at the date of the equity transactions. Translation adjustments are reflected in stockholders’ equity and are included as a component of other comprehensive income (loss). The unrealized gains or losses of intercompany foreign currency transactions that are of a long-term investment nature are reported in other comprehensive income (loss). The unrealized gains and losses of intercompany foreign currency transactions that are of a long-term investment nature for the years ended December 31, 2023, 2022, and 2021 were a $1.1 million gain, a $1.8 million loss, and a $2.6 million loss, respectively.
Comprehensive Income (loss)	Comprehensive Income (loss) The Company’s comprehensive income (loss) includes its foreign currency translation gains and losses, changes in pension obligations as well as its share of other comprehensive income from its equity method investments.
Acquisitions	Acquisitions The Company evaluates acquisitions and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to determine if substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If the screen is met, the transaction is accounted for as an asset acquisition. If the screen is not met, further determination is required as to whether or not the Company has acquired inputs and substantive processes that have the ability to create outputs, which would meet the definition of a business. Acquisitions meeting the definition of business combinations are accounted for using the acquisition method of accounting, which requires that the purchase price be allocated to the net assets acquired at their respective fair values. In a business combination, any excess of the purchase price over the estimated fair values of the net assets acquired is recorded as goodwill. For asset acquisitions, a cost accumulation model is used to determine the cost of an asset acquisition. Direct transaction costs are recognized as part of the cost of an asset acquisition. The cost of an asset acquisition, including transaction costs, is allocated to identifiable assets acquired and liabilities assumed based on a relative fair value basis, with the exception of non-qualifying assets. Goodwill is not recognized in an asset acquisition. When a transaction accounted for as an asset acquisition includes an in-process research and development, or IPR&D, asset, the IPR&D asset is only capitalized if it has an alternative future use other than in a particular research and development project. Asset acquisitions may include contingent consideration arrangements that encompass obligations to make future payments to sellers contingent upon the achievement of future financial targets. Contingent consideration, including assumed contingent considerations, is not recognized until all contingencies are resolved and the consideration is paid or becomes payable (unless contingent considerations meets the definition of a derivative, in which case the amount becomes part of the basis in the asset acquired), at which point the consideration is allocated to the assets acquired based on their relative fair values at the acquisition date, with the exception of non-qualifying assets. Judgments are used in determining estimates of useful lives of long-lived assets. Useful life estimates are based on, among other factors, estimates of expected future net cash flows, the assessment of each asset’s life cycle, and the impact of competitive trends on each asset’s life cycle and other factors. These judgments can materially impact the estimates used to allocate purchase consideration to assets acquired and liabilities assumed, and the resulting timing and amounts charged to or recognized in current and future operating results. For these and other reasons, actual results may vary significantly from estimated results.
Shipping and Handling Costs	Shipping and Handling Costs For the years ended December 31, 2023, 2022, and 2021, the Company included shipping and handling costs of approximately $7.0 million, $7.4 million and $4.3 million, respectively, in selling, distribution and marketing expenses in the accompanying consolidated statements of operations.
Advertising Expense	Advertising Expense Advertising expenses, primarily associated with Primatene MIST ®
Research and Development Costs	Research and Development Costs Research and development costs are charged to expense as incurred and consist of costs incurred to further the Company’s research and development activities. These include salaries and related employee benefits, costs associated with clinical trials, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers. The Company may produce or purchase inventories prior to or with the expectation of receiving regulatory approval in the near term, based on operational decisions about the most effective use of existing resources. This inventory is referred to as pre-launch inventory. It is the Company’s accounting policy that the pre-launch inventory is capitalized if it has a probable future economic benefit at the time it is purchased or manufactured. If regulatory approval is received and previously expensed pre-launch inventory is sold, such sales may contribute up to a 100% margin to the Company’s operating results. Pre-launch inventory costs include cost of work in process, materials, and finished drug products. For the years ended December 31, 2023, 2022, and 2021, the Company did not have material capitalized pre-launch inventory.
Financial Instruments	Financial Instruments The Company’s accompanying consolidated balance sheets include the following financial instruments: cash and cash equivalents, restricted cash, accounts receivable, accounts payable, accrued expenses, short-term borrowings and long-term obligations. The Company considers the carrying amounts of current assets and liabilities on the consolidated balance sheets to approximate the fair value of these financial instruments due to the short maturity of these items. The carrying value of the Company’s long-term obligations, with the exception of the convertible debt (See Note 15) approximates their fair value, as the stated borrowing rates are comparable to rates currently offered to the Company for instruments with similar maturities. Investments and short-term investments are recorded at fair value based on quoted prices from recognized security exchanges and other methods (See Note 9). The Company at times enters into interest rate swap contracts to manage its exposure to interest rate changes and its overall cost of long-term debt. The Company’s interest rate swap contracts exchange the variable interest rates for fixed interest rates. From time to time, the Company may enter into forward currency contracts to lock in currency exchange rates to manage its foreign currency exchange rate exposure. The Company’s interest rate swaps and forward currency contracts have not been designated as hedging instruments and, therefore are recorded at their fair values at the end of each reporting period with changes in fair value recorded in other income (expenses) on the consolidated statements of operations. As of December 31, 2023, the Company did not have any unsettled forward currency contracts to purchase foreign currency. As of December 31, 2022, the Company had an unsettled forward currency contract to purchase foreign currency with a fair value of approximately $0.2 million based on Level 2 inputs, which was recorded as a liability in accounts payable and accrued liabilities in the accompanying consolidated balance sheets.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash, money market accounts, certificates of deposit and highly liquid investments with original maturities of three months or less.
Investments	Investments Investments as of December 31, 2023 and 2022 consisted of certificates of deposit and investment grade corporate, agency, and municipal bonds with original maturity dates between three and fifteen months.
Restricted Cash	Restricted Cash Restricted cash is collateral required for the Company to guarantee certain vendor payments in France. As of December 31, 2023 and 2022, the restricted cash balance was $0.2 million.
Restricted Short-Term Investments	Restricted Short-Term Investments Restricted short-term investments consist of certificates of deposit that are collateral for standby letters of credit to qualify for workers’ compensation self-insurance. The certificates of deposit have original maturities greater than three months, but less than one year. As of December 31, 2023 and 2022, the balance of restricted short-term investments was $2.2 million.
Allowance for Credit Losses	Allowance for Credit Losses The Company evaluates the collectability of accounts receivable based on a combination of factors. When the Company is aware of circumstances that may impair a customer’s ability to pay subsequent to the original sale, the Company records a specific allowance to reduce the amounts receivable to the amount that the Company reasonably believes to be collectable. For all other customers, the Company recognizes an allowance for credit losses based on factors that include the length of time the receivables are past due, industry and geographic concentrations, the current economic conditions and historical collection experience. As of December 31, 2023 and 2022, the Company's allowance for credit losses was $2.8 million and $2.7 million, respectively.
Inventories	Inventories Inventories consist of currently marketed products and products manufactured under contract. Inventories are stated using the first-in, first-out method, on a consistent basis. The Company states inventory at the lower of cost or net realizable value. Provisions are made for slow moving, unsellable, or obsolete items. Net realizable value is determined using the estimated selling price, in the ordinary course of business, less estimated costs to complete and dispose.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment are stated at cost or, in the case of assets acquired in a business combination, at fair value on the purchase date. Depreciation and amortization expense is computed using the straight-line method over the estimated useful lives of the related assets as follows:
Intangible Assets	Intangible Assets Intangible assets with finite lives are amortized using the straight-line method over the period the asset is expected to contribute directly or indirectly to the future cash flows of the Company as follows:
Impairment of Long Lived Assets, including Identifiable Definite-Lived Intangible Assets	Impairment of Long-Lived Assets, including Identifiable Definite-Lived Intangible Assets The Company assesses long-term and identifiable definite-lived intangible assets or asset groups for impairment when events or changes in circumstances indicate that the carrying amount of an asset or asset group may not be recoverable. If the sum of the expected future undiscounted cash flows is less than the carrying amount of the asset or an asset group, further impairment analysis is performed. An impairment loss is measured as the amount by which the carrying amount of the asset or asset groups exceeds the fair value (assets to be held and used) or fair value less cost to sell (assets to be disposed of). The Company also assesses the useful lives of its assets periodically to determine whether events and circumstances warrant a revision to the remaining useful life. Changes in the useful life are adjusted prospectively by revising the remaining period over which the asset is amortized.
Deferred Income Taxes	Deferred Income Taxes The Company utilizes the liability method of accounting for income taxes, under which deferred taxes are determined based on the temporary differences between the financial statements and the tax basis of assets and liabilities using enacted tax rates. A valuation allowance is recorded when it is more likely than not that the deferred tax assets will not be realized.
Debt Issuance Costs	Debt Issuance Costs Debt issuance costs related to non-revolving debt are recognized as a reduction to the related debt balance in the accompanying consolidated balance sheets and amortized to interest expense over the contractual term of the related debt using the effective interest method. Debt issuance costs associated with revolving debt are capitalized within other long-term assets on the consolidated balance sheets and are amortized to interest expense over the term of the related revolving debt.
Convertible Debt	Convertible Debt The Company accounts for its convertible debt instruments as a single unit of accounting, a liability, because the Company concluded that the conversion features do not require bifurcation as a derivative under Accounting Standards Codification, or ASC, 815-15, Derivatives and Hedging In accordance with ASU 2020-06, Debt—Debt with Conversion and Other Options (Subtopic 470-20) and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815-40) Debt with Conversion and Other Options
Impairment of Indefinite-Lived Intangible Asset and Goodwill	Impairment of Indefinite-Lived Intangible Asset and Goodwill The Company assesses indefinite lived intangible asset and goodwill for impairment in the fourth quarter of each year or more frequently if indicators of impairment are present. When the Company chooses to perform a qualitative assessment, it evaluates economic, industry and company-specific factors as an initial step. If the Company determines it is more likely than not that the indefinite-lived intangible asset is impaired or the fair value of a reporting unit is less than its carrying amount, further quantitative impairment testing is then performed; otherwise, no further testing is required. An impairment loss is recorded if the asset’s fair value is less than its carrying value. The Company also periodically assesses its indefinite-lived intangible asset to determine if events and circumstances continue to support an indefinite useful life. If the life is no longer indefinite, the asset is tested for impairment. The carrying value, after recognition of any impairment loss, is amortized over its remaining useful life.
Self-Insured Claims	Self-Insured Claims The Company is self-insured, up to certain limits, for workers’ compensation claims. The Company has purchased stop-loss insurance, which will reimburse the Company for individual claims in excess of $350,000 or aggregate minimum attachment of $4.8 million annually. The cost of claims reported and an estimate of claims incurred but not reported are charged to operating expenses. A liability for unpaid claims and the associated claim expenses, including incurred but not reported losses, is actuarially determined and reflected in accrued liabilities in the accompanying consolidated balance sheets. Total expense under the program was approximately $1.7 million, $0.3 million, and $0.5 million, for the years ended December 31, 2023, 2022 and 2021, respectively. The self-insured claims liability was $4.3 million and $3.7 million at December 31, 2023 and 2022, respectively. The determination of such claims and expenses and the appropriateness of the related liability is reviewed periodically and updated, as necessary. Changes in estimates are recorded in the period identified.
Litigation, Commitments and Contingencies	Litigation, Commitments and Contingencies Litigation, commitments and contingencies are accrued when management, after considering the facts and circumstances of each matter as then known to management, has determined it is probable a liability will be found to have been incurred and the amount of the loss can be reasonably estimated. When only a range of amounts is reasonably estimable and no amount within the range is more likely than another, the low end of the range is recorded. Legal fees are expensed as incurred. Due to the inherent uncertainties surrounding gain contingencies, the Company generally does not recognize potential gains until they are realized. In 2021, the Company settled a legal dispute with an unaffiliated third party and subsequently received a settlement payment, net of contingent legal fees, in the amount of $2.7 million. The net amount of $2.7 million was recorded as other income in other income (expense), net in the consolidated statements of operations for the year ended December 31, 2021.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In November 2023, the Financial Accounting Standards Board, or FASB, issued Accounting Standard Update 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures In December 2023, the FASB issued Accounting Standard Update 2023-09, Income taxes (Topic 740): Improvements to Income Tax Disclosures

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
Summary of Significant Accounting Policies (Tables)	Dec. 31, 2023
Summary of Significant Accounting Policies
Schedule of estimated useful life of property, plant and equipment	Buildings 20 - 31 years Machinery and equipment 3 - 12 years Furniture and fixtures 3 - 7 years Automobiles 4 - 5 years Leasehold improvements Lesser of remaining lease term or useful life
Schedule of estimated useful life of intangible assets	Product rights 10 - 24 years Patents 10 - 20 years Land-use rights 37 - 50 years

BAQSIMI Acquisition (Tables)

BAQSIMI Acquisition (Tables)	12 Months Ended
BAQSIMI Acquisition (Tables)	Dec. 31, 2023
BAQSIMI Acquisition
Summary of aggregate amount paid for assets acquired	Fair Value (in thousands) Cash payment $ 500,000 Fair value of deferred cash payments 121,699 Transaction costs 6,406 Total purchase price $ 628,105
Schedule of purchase price allocated to acquired assets	Fair Value (in thousands) Property, plant, and equipment $ 34,426 BAQSIMI ® 591,338 Deferred tax assets 2,341 Total assets acquired $ 628,105

Revenue Recognition (Tables)

Revenue Recognition (Tables)	12 Months Ended
Revenue Recognition (Tables)	Dec. 31, 2023
Revenue Recognition
Schedule of chargeback and rebates provision analysis	Year Ended December 31, 2023 2022 (in thousands) Beginning balance $ 26,606 $ 20,167 Provision for chargebacks and rebates 257,219 208,081 Credits and payments issued to third parties (255,905) (201,642) Ending balance $ 27,920 $ 26,606
Schedule of provision of chargebacks and rebates as reflected in the balance sheets	December 31, 2023 2022 (in thousands) Reduction to accounts receivable, net $ 21,861 $ 20,460 Accounts payable and accrued liabilities 6,059 6,146 Total $ 27,920 $ 26,606
Schedule of product return liability analysis	Year Ended December 31, 2023 2022 (in thousands) Beginning balance $ 19,451 $ 21,677 Provision for product returns 4,275 4,405 Credits issued to third parties (6,547) (6,631) Ending balance $ 17,179 $ 19,451
Schedule of provision for product returns as reflected in the balance sheets	December 31, 2023 2022 (in thousands) Accounts payable and accrued liabilities $ 12,263 $ 14,867 Other long-term liabilities 4,916 4,584 Total $ 17,179 $ 19,451

Income per Share Attributable_2

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders (Tables)	12 Months Ended
	Dec. 31, 2023
Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders
Schedule of basic and diluted net income (loss) per share calculation	Year Ended December 31, 2023 2022 2021 (in thousands, except per share data) Basic and dilutive numerator: Net income attributable to Amphastar Pharmaceuticals, Inc. stockholders $ 137,545 $ 91,386 $ 62,116 Denominator: Weighted-average shares outstanding — basic 48,265 48,551 47,777 Net effect of dilutive securities: Incremental shares from equity awards 4,736 3,876 2,007 Weighted-average shares outstanding — diluted 53,001 52,427 49,784 Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — basic $ 2.85 $ 1.88 $ 1.30 Net income per share attributable to Amphastar Pharmaceuticals, Inc. stockholders — diluted $ 2.60 $ 1.74 $ 1.25

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
Segment Reporting (Tables)	Dec. 31, 2023
Segment Reporting
Schedule of financial information by reporting segment	Year Ended December 31, 2023 2022 2021 (in thousands) Net revenues: Finished pharmaceutical products $ 630,273 $ 486,505 $ 419,570 API 14,122 12,482 18,198 Total net revenues 644,395 498,987 437,768 Gross profit (loss): Finished pharmaceutical products 367,325 256,710 209,715 API (16,204) (7,850) (9,976) Total gross profit 351,121 248,860 199,739 Operating expenses 154,134 141,363 129,852 Income from operations 196,987 107,497 69,887 Non-operating (expenses) income (25,628) 8,543 14,252 Income before income taxes $ 171,359 $ 116,040 $ 84,139
Schedule of net revenues in the finished pharmaceutical products segment	Year Ended December 31, 2023 2022 2021 (in thousands) Finished pharmaceutical products segment net revenues: Glucagon $ 113,684 $ 55,322 $ 47,639 Primatene MIST ® 89,321 84,309 73,113 Epinephrine 81,650 74,204 57,530 Lidocaine 58,162 52,539 44,413 Phytonadione 44,939 49,500 45,498 Enoxaparin 31,533 34,950 35,962 Naloxone 19,004 26,269 27,540 Other finished pharmaceutical products 140,823 109,412 87,875 Total finished pharmaceutical products net revenues 579,116 486,505 419,570 BAQSIMI ® 51,157 — — Total finished pharmaceutical products segment net revenues $ 630,273 $ 486,505 $ 419,570
Schedule of depreciation and amortization expense by reporting segment	Year Ended December 31, 2023 2022 2021 (in thousands) Depreciation and amortization expense Finished pharmaceutical products $ 21,794 $ 8,884 $ 6,003 API 3,943 3,713 4,222 Total depreciation and amortization expense $ 25,737 $ 12,597 $ 10,225
Schedule of net revenues and carrying values of long-lived assets by geographic region	Net Revenue Long-Lived Assets Year Ended December 31, December 31, 2023 2022 2021 2023 2022 (in thousands) United States (1) $ 635,192 $ 486,833 $ 419,869 $ 765,102 $ 136,328 China 4,505 4,697 6,020 91,913 88,647 France 4,698 7,457 11,879 37,647 39,598 Total $ 644,395 $ 498,987 $ 437,768 $ 894,662 $ 264,573

Customer and Supplier Concent_2

Customer and Supplier Concentration (Tables)	12 Months Ended
Customer and Supplier Concentration (Tables)	Dec. 31, 2023
Customer and Supplier Concentration
Schedule of accounts receivable and net revenues by major customer	% of Total Accounts % of Net Receivable Revenue December 31, December 31, Year Ended December 31, 2023 2022 2023 2022 2021 McKesson 26 % 32 % 25 % 22 % 21 % Cencora 16 % 16 % 20 % 23 % 24 % Cardinal Health 13 % 19 % 15 % 17 % 16 % Lilly 20 % — 8 % — —

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
Fair Value Measurements (Tables)	Dec. 31, 2023
Fair Value Measurements
Schedule of financial assets and liabilities measured on a recurring basis	Total (Level 1) (Level 2) (Level 3) (in thousands) Cash equivalents $ 116,441 $ 116,441 $ — $ — Restricted cash 235 235 — — Short-term investments 37,142 — 37,142 — Restricted short-term investments 2,200 — 2,200 — Interest rate swaps related to variable rate loans (5,243) — (5,243) — Total assets and liabilities measured at fair value as of December 31, 2023 $ 150,775 $ 116,676 $ 34,099 $ — Total (Level 1) (Level 2) (Level 3) Assets: (in thousands) Cash equivalents $ 130,199 $ 130,199 $ — $ — Restricted cash 235 235 — — Short-term investments 4,600 — 4,600 — Restricted short-term investments 2,200 — 2,200 — Interest rate swaps related to variable rate loans 6,048 — 6,048 — Total assets measured at fair value as of December 31, 2022 $ 143,282 $ 130,434 $ 12,848 $ —

Investments (Tables)

Investments (Tables)	12 Months Ended
Investments (Tables)	Dec. 31, 2023
Investments
Schedule of securities classified as held-to-maturity	Gross Gross Amortized Unrealized Unrealized Fair Cost Gains Losses Value (in thousands) Corporate and agency bonds (due within 1 year) $ 73,815 $ 7 $ (21) $ 73,801 Corporate bonds (due within 1 to 3 years) 14,621 56 (1) 14,676 Municipal bonds (due within 1 year) 1,081 1 — 1,082 Total investments as of December 31, 2023 $ 89,517 $ 64 $ (22) $ 89,559 Corporate and agency bonds (due within 1 year) $ 21,612 $ — $ (60) $ 21,552 Municipal bonds (due within 1 year) 1,903 — (2) 1,901 Total investments as of December 31, 2022 $ 23,515 $ — $ (62) $ 23,453

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
Goodwill and Intangible Assets (Tables)	Dec. 31, 2023
Goodwill and Intangible Assets
Schedule of weighted-average life, original cost, accumulated amortization and net book value by major class	Weighted-Average Accumulated Life (Years) Original Cost Amortization Net Book Value (in thousands) Definite-lived intangible assets BAQSIMI ® (1) 24 $ 591,338 $ 12,319 $ 579,019 IMS (UK) international product rights (2) 10 8,462 8,462 — Patents 12 486 376 110 Land-use rights 39 2,540 815 1,725 Subtotal 23 602,826 21,972 580,854 Indefinite-lived intangible assets Trademark * 29,225 — 29,225 Goodwill - Finished pharmaceutical products * 3,216 — 3,216 Subtotal * 32,441 — 32,441 As of December 31, 2023 * $ 635,267 $ 21,972 $ 613,295 Weighted-Average Accumulated Life (Years) Original Cost Amortization Net Book Value (in thousands) Definite-lived intangible assets IMS (UK) international product rights (2) 10 $ 8,462 $ 5,430 $ 3,032 Patents 12 486 362 124 Land-use rights 39 2,540 749 1,791 Subtotal 11 11,488 6,541 4,947 Indefinite-lived intangible assets Trademark * 29,225 — 29,225 Goodwill - Finished pharmaceutical products * 3,126 — 3,126 Subtotal * 32,351 — 32,351 As of December 31, 2022 * $ 43,839 $ 6,541 $ 37,298 * Intangible assets with indefinite lives have an indeterminable average life. (1) See Note 4. (2) In June 2023, the Company recorded an impairment related to its IMS (UK) international product rights in the amount of $2.7 million. The Company recorded the impairment in the cost of revenue in its consolidated statement of operations for the year ended December 31, 2023
Schedule of changes in carrying amounts of goodwill	December 31, 2023 2022 (in thousands) Beginning balance $ 3,126 $ 3,313 Currency translation 90 (187) Ending balance $ 3,216 $ 3,126
Schedule of finite-lived intangible assets, future amortization expense	(in thousands) 2024 $ 24,718 2025 24,718 2026 24,718 2027 24,718 2028 24,718 Thereafter 457,264 Total amortizable intangible assets 580,854 Indefinite-lived intangibles 32,441 Total intangibles (net of accumulated amortization) $ 613,295

Inventories (Tables)

Inventories (Tables)	12 Months Ended
Inventories (Tables)	Dec. 31, 2023
Inventories
Schedule of inventories	December 31, 2023 2022 (in thousands) Raw materials and supplies $ 50,082 $ 47,607 Work in process 30,822 37,090 Finished goods 24,929 18,887 Total inventories $ 105,833 $ 103,584

Property, Plant, and Equipment

Property, Plant, and Equipment (Tables)	12 Months Ended
Property, Plant, and Equipment (Tables)	Dec. 31, 2023
Property, Plant, and Equipment.
Schedule of property, plant, and equipment	December 31, 2023 2022 (in thousands) Buildings $ 168,771 $ 130,726 Leasehold improvements 41,686 31,535 Land 7,484 7,451 Machinery and equipment 259,484 208,068 Furniture, fixtures, and automobiles 31,943 29,674 Construction in progress 18,676 50,842 Total property, plant, and equipment 528,044 458,296 Less accumulated depreciation (245,298) (220,030) Total property, plant, and equipment, net $ 282,746 $ 238,266

Accounts Payable and Accrued _2

Accounts Payable and Accrued Liabilities (Tables)	12 Months Ended
Accounts Payable and Accrued Liabilities (Tables)	Dec. 31, 2023
Accounts Payable and Accrued Liabilities.
Schedule of accounts payable and accrued liabilities	December 31, 2023 2022 (in thousands) Accrued customer fees and rebates $ 16,702 $ 14,198 Accrued payroll and related benefits 25,203 22,847 Accrued product returns, current portion 12,263 14,867 Accrued loss on firm purchase commitments 918 2,686 Other accrued liabilities 12,842 9,143 Total accrued liabilities 67,928 63,741 Accounts payable 25,438 20,501 Total accounts payable and accrued liabilities $ 93,366 $ 84,242

Debt (Tables)

Debt (Tables)	12 Months Ended
Debt (Tables)	Dec. 31, 2023
Debt
Schedule of debt	December 31, 2023 2022 (in thousands) Convertible Debt 2029 Convertible Notes $ 345,000 $ — Term Loan Wells Fargo Term Loan due June 2028 250,000 — Capital One N.A. Term Loan paid off June 2023 — 68,250 Mortgage Loans Mortgage payable with East West Bank due June 2027 8,016 8,188 Other Loans and Payment Obligations French government loans due December 2026 158 204 Line of Credit Facilities Line of credit facility with China Merchant Bank due October 2026 — — Wells Fargo Revolving line of credit facility due June 2028 — — Capital One N.A. Revolving line of credit facility closed in June 2023 — — Equipment under Finance Leases 616 790 Total debt 603,790 77,432 Less current portion of long-term debt 436 3,046 Less: Loan issuance costs 13,775 1,547 Long-term debt, net of current portion and unamortized debt issuance costs $ 589,579 $ 72,839
Schedule of Maturities of Long-term Debt	Long-term Debt (in thousands) 2024 $ 234 2025 245 2026 254 2027 7,441 2028 250,000 Thereafter 345,000 $ 603,174

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
Income Taxes (Tables)	Dec. 31, 2023
Income Taxes
Schedule of income (loss) before income taxes	Year Ended December 31, 2023 2022 2021 (in thousands) Income before income taxes: United States $ 181,922 $ 127,204 $ 86,236 Foreign (10,563) (11,164) (2,097) Total income before income taxes $ 171,359 $ 116,040 $ 84,139
Summary of provision (benefit) for income taxes	Year Ended December 31, 2023 2022 2021 (in thousands) Current provision: Federal $ 42,689 $ 37,626 $ 14,088 State 1,912 732 1,182 Foreign 1,089 998 1,676 Total current provision 45,690 39,356 16,946 Deferred provision (benefit): Federal (13,134) (16,119) 2,657 State 1,537 816 110 Foreign (2,260) (576) 917 Total deferred provision (13,857) (15,879) 3,684 Total provision for income taxes $ 31,833 $ 23,477 $ 20,630
Schedule of reconciliation of the statutory federal income tax rate	Year Ended December 31, 2023 2022 2021 Statutory federal income tax 21.0 % 21.0 % 21.0 % State tax expense, net of federal tax benefit 1.6 1.1 1.2 Foreign tax rate differences (0.1) (0.3) (2.0) Foreign valuation allowance 0.1 2.6 5.5 Research and development credits (4.2) (3.1) (3.2) Share-based compensation (3.2) (3.5) (0.2) Executive compensation 2.4 2.3 2.3 Employee-related expenses — 0.2 0.1 Intercompany transfer of assets other than inventory 0.6 — — Other 0.4 (0.1) (0.2) Effective tax rate 18.6 % 20.2 % 24.5 %
Summary of deferred tax assets and liabilities	December 31, 2023 2022 (in thousands) Deferred tax assets: Research and development credits $ 12,759 $ 15,418 Net operating loss carryforward 20,156 20,019 Inventory capitalization and reserve 12,381 9,598 Share-based compensation 5,464 5,208 Operating leases 8,360 6,684 Accrued expenses 5,970 4,956 Accrued chargebacks 5,441 5,125 Product return allowance 4,927 5,464 Intangibles 2,124 2,124 Research and development capitalization 34,036 17,988 Total deferred tax assets 111,618 92,584 Deferred tax liabilities: Depreciation/amortization 21,630 13,272 Intangibles 4,367 8,564 Operating leases 8,037 6,398 Federal impact of state deferred taxes 3,577 3,800 Other 260 2,467 Total deferred tax liabilities 37,871 34,501 Valuation allowance (20,495) (19,700) Net deferred tax assets $ 53,252 $ 38,383
Schedule of unrecognized tax benefits	December 31, 2023 2022 2021 (in thousands) Balance at the beginning of the year $ 12,895 $ 11,796 $ 10,053 Deductions based on tax positions related to prior year — (41) — Additions based on tax positions related to the current year 2,074 1,643 1,754 Deductions based on statute of limitations (2,476) (503) (11) Balance at the end of the year $ 12,493 $ 12,895 $ 11,796

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
Stockholders' Equity (Tables)	Dec. 31, 2023
Stockholders' Equity
Schedule of key assumptions to determine fair value of options	Year Ended December 31, 2023 2022 2021 Average volatility 41.4 % 41.0 % 42.1 % Average risk-free interest rate 4.1 % 2.3 % 1.2 % Weighted-average expected life in years 6.2 6.1 6.1 Dividend yield rate — % — % — %
Schedule of the summary of option activity under all plans	Weighted-Average Weighted-Average Remaining Aggregate Exercise Contractual Intrinsic Options Price Term (Years) Value (1) (in thousands) Outstanding as of December 31, 2022 7,929,150 $ 17.66 Options granted 759,820 35.84 Options exercised (920,817) 15.40 Options forfeited (5,312) 30.82 Options expired (543) 16.25 Outstanding as of December 31, 2023 7,762,298 $ 19.70 4.54 $ 327,155 Exercisable as of December 31, 2023 5,685,943 $ 16.55 3.25 $ 257,560 Vested and expected to vest as of December 31, 2023 7,601,023 $ 19.46 4.46 $ 322,203
Schedule of information relating to options grants	Year Ended December 31, 2023 2022 2021 (in thousands, except per share data) Weighted-average grant date fair value per share $ 16.76 $ 14.75 $ 7.62 Intrinsic value of options exercised 29,918 21,279 7,906 Cash received from options exercised 14,172 19,202 16,757 Total fair value of the options vested during the period 8,890 8,174 8,177
Schedule of the summary of nonvested options status	Weighted-Average Grant Date Options Fair Value Non-vested as of December 31, 2022 2,378,453 $ 9.48 Options granted 759,820 16.76 Options vested (1,056,606) 8.41 Options forfeited (5,312) 13.94 Non-vested as of December 31, 2023 2,076,355 12.68
Schedule of information relating to RSU grants and deliveries	Total Fair Market Total RSUs Value of RSUs Issued Issued (1) (in thousands) RSUs outstanding at December 31, 2022 1,007,052 RSUs granted 356,176 $ 12,725 RSUs forfeited (2,368) RSUs vested (2) (440,484) RSUs outstanding at December 31, 2023 920,376 (1) The total FMV is derived from the number of RSUs granted times the current stock price on the date of grant. (2) Of the vested RSUs, 168,067 shares of common stock were surrendered to fulfil tax withholding obligations.
Schedule of recorded share-based compensation expense under all plans	Year Ended December 31, 2023 2022 2021 (in thousands) Cost of revenues $ 4,891 $ 4,179 $ 3,778 Operating expenses: Selling, distribution, and marketing 870 726 596 General and administrative 12,269 11,180 12,622 Research and development 2,212 1,775 1,691 Total share-based compensation $ 20,242 $ 17,860 $ 18,687

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
Commitments and Contingencies (Tables)	Dec. 31, 2023
Commitments and Contingencies
Schedule of lease information	The components of lease costs were as follows: Year Ended December 31, 2023 2022 2021 (in thousands) Operating lease costs $ 5,267 $ 4,709 $ 4,328 Short-term lease costs 332 300 518 Finance lease costs Amortization of right-of-use assets 189 237 384 Interest on lease liabilities 45 26 26 Total finance lease costs $ 234 $ 263 $ 410 Total lease costs $ 5,833 $ 5,272 $ 5,256 Other information pertaining to leases is as follows: Year Ended December 31, 2023 2022 2021 (in thousands, except lease term and discount rate) Cash paid for amounts included in the measurement of lease liabilities Operating cash flows paid for operating leases $ 5,106 $ 4,329 $ 4,446 Operating cash flows paid for finance leases 40 18 25 Financing cash flows paid for finance leases 154 233 310 Right-of use assets obtained in exchange for lease liabilities Operating leases 10,521 2,166 11,041 Finance leases — 642 110 Weighted-average remaining lease term (years) Operating leases 7.7 8.7 9.5 Finance leases 3.4 4.3 2.4 Weighted-average discount rate Operating leases 5.5 % 4.4 % 4.5 % Finance leases 6.7 % 6.7 % 5.2 %
Schedule of future minimum rental payments for operating leases	Operating Finance Leases Leases Total (in thousands) 2024 $ 5,611 $ 236 $ 5,847 2025 5,536 190 5,726 2026 5,586 158 5,744 2027 5,359 104 5,463 2028 4,605 — 4,605 Thereafter 14,805 — 14,805 Total lease payments $ 41,502 $ 688 $ 42,190 Less: interest 7,875 72 7,947 Total $ 33,627 $ 616 $ 34,243

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Gains and (losses) of intercompany foreign currency transactions		$ 1,100,000	$ (1,800,000)	$ (2,600,000)
Selling, distribution, and marketing		28,853,000	21,531,000	17,486,000
Allowance for Credit Losses		2,800,000	2,700,000
Forward Currency Contracts Liabilities		0	200,000
Restricted cash		235,000	235,000
Certificates of deposit		2,200,000	2,200,000
Amount retained, individual claims		350,000
Amount retained, aggregate claims		4,800,000
Actuarially Determined Self-insurance Expense		1,700,000	300,000	500,000
Self-insurance Claims Liability		4,300,000	3,700,000
Settled Litigation [Member]
Litigation Settlement, Amount Awarded from Other Party	$ 2,700,000
Finished Pharmaceutical Products Segment \| Primatene Mist
Advertising expense		10,400,000	8,700,000	8,100,000
Shipping and Handling [Member]
Selling, distribution, and marketing		$ 7,000,000	$ 7,400,000	$ 4,300,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies (Schedule of PP&E Useful Lives) (Details)	Dec. 31, 2023
Buildings [Member] \| Minimum
Property, Plant and Equipment
Useful life	20 years
Buildings [Member] \| Maximum
Property, Plant and Equipment
Useful life	31 years
Machinery and equipment [Member] \| Minimum
Property, Plant and Equipment
Useful life	3 years
Machinery and equipment [Member] \| Maximum
Property, Plant and Equipment
Useful life	12 years
Furniture and fixtures [Member] \| Minimum
Property, Plant and Equipment
Useful life	3 years
Furniture and fixtures [Member] \| Maximum
Property, Plant and Equipment
Useful life	7 years
Automobiles [Member] \| Minimum
Property, Plant and Equipment
Useful life	4 years
Automobiles [Member] \| Maximum
Property, Plant and Equipment
Useful life	5 years

Summary of Significant Accoun_6

Summary of Significant Accounting Policies (Schedule of Intangible Useful Lives) (Details)	Dec. 31, 2023	Dec. 31, 2022
Useful life of intangibles	23 years	11 years
Product Rights [Member] \| Minimum
Useful life of intangibles	10 years
Product Rights [Member] \| Maximum
Useful life of intangibles	24 years
Patents
Useful life of intangibles	12 years	12 years
Patents \| Minimum
Useful life of intangibles	10 years
Patents \| Maximum
Useful life of intangibles	20 years
Land-Use Rights [Member]
Useful life of intangibles	39 years	39 years
Land-Use Rights [Member] \| Minimum
Useful life of intangibles	37 years
Land-Use Rights [Member] \| Maximum
Useful life of intangibles	50 years

ANP Restructuring (Details)

ANP Restructuring (Details)	Dec. 31, 2023
Hanxin \| Hanxin
Restructuring and Related Cost [Line Items]
Ownership after transaction	11.50%

BAQSIMI Acquisition (Narrative)

BAQSIMI Acquisition (Narrative) (Details) $ in Thousands			12 Months Ended
BAQSIMI Acquisition (Narrative) (Details) $ in Thousands	Jun. 30, 2023 USD ($)	Apr. 21, 2023 USD ($)	Dec. 31, 2023 USD ($)
Wells Fargo Bank \| Revolving Credit Facility
Asset Acquisition [Line Items]
Maximum borrowing capacity	$ 200,000
Wells Fargo Bank \| Secured debt \| Senior secured revolving credit facility
Asset Acquisition [Line Items]
Maximum borrowing capacity	$ 200,000
BAQSIMI product rights
Asset Acquisition [Line Items]
Estimated useful life of acquired intangible asset	24 years
Cash payment		$ 500,000
Contingent consideration		450,000
Earnout obligations		125,000
Deferred payment including accrued interest	$ 129,000
Interest expense accretion period	1 year
Interest expense recognized related to accretion of deferred payment			$ 3,700
Asset Acquisition Transaction Cost		$ 6,406
BAQSIMI product rights \| Maximum
Asset Acquisition [Line Items]
Payment period following transaction closing		18 months
BAQSIMI product rights \| Maximum \| Manufacturing Services Agreement
Asset Acquisition [Line Items]
Agreement term	18 months
BAQSIMI product rights \| Maximum \| Transition Services Agreement
Asset Acquisition [Line Items]
Agreement term	18 months
BAQSIMI product rights \| Wells Fargo Bank \| Secured debt
Asset Acquisition [Line Items]
Principal amount	$ 700,000
Debt proceeds	500,000
Aggregate principal amount	$ 700,000
BAQSIMI product rights \| Payment on the first anniversary of the closing
Asset Acquisition [Line Items]
Guaranteed payment payable		$ 125,000
BAQSIMI product rights \| Payment after the first anniversary of the closing, but no later than 18 months after the closing
Asset Acquisition [Line Items]
Guaranteed payment payable		4,000
BAQSIMI product rights \| Asset Acquisition, Contingent Consideration, Sales Milestone Achievement One [Member]
Asset Acquisition [Line Items]
Threshold of annual sales milestone		$ 175,000
Period after closing considered for achievement of sales milestone		5 years
Asset Acquisition Transaction Cost		$ 100,000
BAQSIMI product rights \| Asset Acquisition, Contingent Consideration, Sales Milestone Achievement Two [Member]
Asset Acquisition [Line Items]
Contingent consideration		$ 100,000
Period after closing considered for achievement of sales milestone		5 years
Number of potential contingent consideration payments		2
Threshold annual net sales milestone achievement for payment of earnout liability		$ 200,000
BAQSIMI product rights \| Asset Acquisition, Contingent Consideration, Sales Milestone Achievement Three [Member]
Asset Acquisition [Line Items]
Contingent consideration		150,000
Threshold of annual sales milestone		$ 950,000
Period after closing considered for achievement of sales milestone		5 years
BAQSIMI product rights \| Asset Acquisition, Earnout Liability, Sales Milestone Achievement One [Member]
Asset Acquisition [Line Items]
Threshold annual net sales milestone achievement for payment of earnout liability		$ 350,000
BAQSIMI product rights \| Asset Acquisition, Earnout Liability, Sales Milestone Achievement Two [Member]
Asset Acquisition [Line Items]
Threshold annual net sales milestone achievement for payment of earnout liability		400,000
BAQSIMI product rights \| Asset Acquisition, Earnout Liability, Sales Milestone Achievement Three [Member]
Asset Acquisition [Line Items]
Threshold annual net sales milestone achievement for payment of earnout liability		$ 600,000

BAQSIMI Acquisition (Aggregate

BAQSIMI Acquisition (Aggregate Amount Paid for Assets Acquired) (Details) - BAQSIMI product rights $ in Thousands	Apr. 21, 2023 USD ($)
Asset Acquisition [Line Items]
Cash payment	$ 500,000
Fair value of deferred cash payment	121,699
Transaction costs	6,406
Total purchase price	$ 628,105

BAQSIMI Acquisition (Purchase P

BAQSIMI Acquisition (Purchase Price Allocated to Acquired Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Apr. 21, 2023	Dec. 31, 2022
Asset Acquisition [Line Items]
Property, plant, and equipment	$ 282,746		$ 238,266
Deferred tax assets	$ 2,124		$ 2,124
BAQSIMI product rights
Asset Acquisition [Line Items]
Property, plant, and equipment		$ 34,426
BAQSIMI product rights		591,338
Deferred tax assets		2,341
Total assets acquired		$ 628,105

Revenue Recognition (Revenues f

Revenue Recognition (Revenues from BAQSIMI sales, net of cost of revenues and transition services fees) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cost of Revenue	$ 293,274	$ 250,127	$ 238,029
Total net revenues	644,395	498,987	437,768
ANP \| Research and development services
Total net revenues	$ 4,500	$ 4,300	$ 5,100

Revenue Recognition (Analysis o

Revenue Recognition (Analysis of the Chargeback Provision) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenue	$ 644,395	$ 498,987	$ 437,768
Beginning balance	26,606	20,167
Provision for chargebacks and rebates	257,219	208,081
Credits and payments issued to third parties	(255,905)	(201,642)
Ending balance	27,920	26,606	20,167
Research and development services \| ANP
Revenue	$ 4,500	$ 4,300	$ 5,100
Minimum
Payment terms	30 days
Settlement of chargebacks and rebates terms	20 days
Maximum
Payment terms	75 days
Settlement of chargebacks and rebates terms	60 days

Revenue Recognition (Chargeback

Revenue Recognition (Chargebacks and Rebates Balance Sheet Accounts) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Total	$ 27,920	$ 26,606	$ 20,167
Accounts receivable, net
Total	21,861	20,460
Accounts payable and accrued liabilities
Total	$ 6,059	$ 6,146

Revenue Recognition (Analysis_2

Revenue Recognition (Analysis of Product Return Liability) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Provision for product returns	$ 17,179	$ 19,451
Aggregate product return rate	1.10%	1.40%
Return accrual included in accounts payable and accrued liabilities	$ 12,263	$ 14,867
Product returns
Beginning balance	19,451	21,677
Provision for product returns	4,275	4,405
Credits issued to third parties	(6,547)	(6,631)
Ending balance	17,179	19,451
Accounts payable and accrued liabilities
Provision for product returns	12,263	14,867
Other Long-Term Liabilities
Provision for product returns	$ 4,916	$ 4,584

Income per Share Attributable_3

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders (Narrative) (Details) - Employee and non-employee stock options - $ / shares	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Earnings Per Share, Shares	0	704,483	1,906,029
Antidilutive Securities Excluded from Computation of Earnings Per Share, Exercise Price of Excluded Securities		$ 34.79	$ 20.82

Income per Share Attributable_4

Income per Share Attributable to Amphastar Pharmaceuticals, Inc. Stockholders (Calculation of Basic and Diluted Net Income (Loss) Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Basic and dilutive numerator:
Net Income (Loss)	$ 137,545	$ 91,386	$ 62,116
Denominator:
Weighted-average shares outstanding-basic	48,265	48,551	47,777
Net effect of dilutive securities:
Incremental shares from equity awards	4,736	3,876	2,007
Weighted-average shares outstanding - diluted	53,001	52,427	49,784
Net income (loss) per share - basic	$ 2.85	$ 1.88	$ 1.30
Net income (loss) per share - diluted	$ 2.60	$ 1.74	$ 1.25

Segment Reporting (Selected Fin

Segment Reporting (Selected Financial Information by Reporting Segment) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) segment	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Segment Reporting Information [Line Items]
Number of Reportable Segments \| segment	2
Net revenues:
Total net revenues	$ 644,395	$ 498,987	$ 437,768
Gross profit (loss):
Gross Profit	351,121	248,860	199,739
Operating expenses	154,134	141,363	129,852
Income from operations	196,987	107,497	69,887
Non-operating income (expenses)	(25,628)	8,543	14,252
Income (loss) before income taxes	171,359	116,040	84,139
Finished Pharmaceutical Products Segment
Net revenues:
Total net revenues	630,273	486,505	419,570
Gross profit (loss):
Gross Profit	367,325	256,710	209,715
Active Pharmaceutical Ingredient Segment
Net revenues:
Total net revenues	14,122	12,482	18,198
Gross profit (loss):
Gross Profit	$ (16,204)	$ (7,850)	$ (9,976)

Segment Reporting (Summary of N

Segment Reporting (Summary of Net Revenues by Product Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	$ 644,395	$ 498,987	$ 437,768
Finished Pharmaceutical Products Segment
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	630,273	486,505	419,570
Finished Pharmaceutical Products Segment \| Glucagon
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	113,684	55,322	47,639
Finished Pharmaceutical Products Segment \| Primatene Mist
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	89,321	84,309	73,113
Finished Pharmaceutical Products Segment \| Epinephrine
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	81,650	74,204	57,530
Finished Pharmaceutical Products Segment \| Lidocaine
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	58,162	52,539	44,413
Finished Pharmaceutical Products Segment \| Phytonadione
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	44,939	49,500	45,498
Finished Pharmaceutical Products Segment \| Enoxaparin
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	31,533	34,950	35,962
Finished Pharmaceutical Products Segment \| Naloxone
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	19,004	26,269	27,540
Finished Pharmaceutical Products Segment \| Other Finished Pharmaceutical Products
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	140,823	109,412	87,875
Finished Pharmaceutical Products Segment \| Total finished pharmaceutical products net revenues
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	579,116	$ 486,505	$ 419,570
Finished Pharmaceutical Products Segment \| BAQSIMI
Segment Reporting Information, Revenue for Reportable Segment [Abstract]
Total net revenues	$ 51,157

Segment Reporting (Depreciation

Segment Reporting (Depreciation and Amortization Expense by Reporting Segment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 25,737	$ 12,597	$ 10,225
Finished Pharmaceutical Products Segment
Segment Reporting Information [Line Items]
Depreciation and amortization expense	21,794	8,884	6,003
Active Pharmaceutical Ingredient Segment
Segment Reporting Information [Line Items]
Depreciation and amortization expense	$ 3,943	$ 3,713	$ 4,222

Segment Reporting (Summary of R

Segment Reporting (Summary of Revenues and Long-Lived Assets by Geographic Region) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenues	$ 644,395	$ 498,987	$ 437,768
Long-Lived Assets	894,662	264,573
UNITED STATES
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenues	635,192	486,833	419,869
Long-Lived Assets	765,102	136,328
CHINA
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenues	4,505	4,697	6,020
Long-Lived Assets	91,913	88,647
FRANCE
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net revenues	4,698	7,457	$ 11,879
Long-Lived Assets	$ 37,647	$ 39,598

Customer and Supplier Concent_3

Customer and Supplier Concentration (Details) - Customer Concentration Risk [Member]	12 Months Ended
	Dec. 31, 2023 customer item	Dec. 31, 2022 customer item	Dec. 31, 2021 item
Revenue, Major Customer [Line Items]
Number of major customers that are wholesale distributors	3
Accounts receivable, net
Revenue, Major Customer [Line Items]
Number of major customers \| customer	4	4
Net Revenue
Revenue, Major Customer [Line Items]
Number of major customers	4	4	4
Cencora [Member] \| Accounts receivable, net
Revenue, Major Customer [Line Items]
Major Customers	16%	16%
Cencora [Member] \| Net Revenue
Revenue, Major Customer [Line Items]
Major Customers	20%	23%	24%
Cardinal Health [Member] \| Accounts receivable, net
Revenue, Major Customer [Line Items]
Major Customers	13%	19%
Cardinal Health [Member] \| Net Revenue
Revenue, Major Customer [Line Items]
Major Customers	15%	17%	16%
McKesson [Member] \| Accounts receivable, net
Revenue, Major Customer [Line Items]
Major Customers	26%	32%
McKesson [Member] \| Net Revenue
Revenue, Major Customer [Line Items]
Major Customers	25%	22%	21%
Eli Lilly and Co [Member] \| Accounts receivable, net
Revenue, Major Customer [Line Items]
Major Customers	20%
Eli Lilly and Co [Member] \| Net Revenue
Revenue, Major Customer [Line Items]
Major Customers	8%

Fair Value Measurements (Fair V

Fair Value Measurements (Fair Values of the Company's Financial Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Recurring Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		$ 130,199
Restricted cash	$ 235	235
Short-term investments	37,142	4,600
Restricted short-term investments	2,200	2,200
Interest rate swaps related to variable rate loans		6,048
Total assets measured at fair value	150,775	143,282
Recurring Basis \| Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps related to variable rate loans	(5,243)
Recurring Basis \| Money market
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	116,441
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents		130,199
Restricted cash	235	235
Total assets measured at fair value	116,676	130,434
Level 1 \| Money market
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	116,441
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	37,142	4,600
Restricted short-term investments	2,200	2,200
Interest rate swaps related to variable rate loans		6,048
Total assets measured at fair value	34,099	$ 12,848
Level 2 \| Interest rate swaps
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest rate swaps related to variable rate loans	$ (5,243)

Investments (Held-to-Maturity)

Investments (Held-to-Maturity) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	$ 89,517	$ 23,515
Gross Unrealized Gains	64
Gross Unrealized Losses	(22)	(62)
Fair Value	89,559	23,453
Corporate and Agency Bonds (due within 1 year)
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	73,815	21,612
Gross Unrealized Gains	7
Gross Unrealized Losses	(21)	(60)
Fair Value	73,801	21,552
Corporate bonds (due within 1 to 3 years)
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	14,621
Gross Unrealized Gains	56
Gross Unrealized Losses	(1)
Fair Value	14,676
Municipal Bonds [Member]
Schedule of Held-to-maturity Securities [Line Items]
Amortized Cost	1,081	1,903
Gross Unrealized Gains	1
Gross Unrealized Losses		(2)
Fair Value	$ 1,082	$ 1,901

Investments (Equity Method Inve

Investments (Equity Method Investment) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Restructuring and Related Cost
Equity in losses of unconsolidated affiliates	$ (1,981)	$ (1,177)	$ (208)
Hanxin
Restructuring and Related Cost
Equity in losses of unconsolidated affiliates	$ 2,000	$ 1,200	$ 200

Goodwill and Intangible Asset_2

Goodwill and Intangible Assets (Summary of Intangible Assets) (Details) - USD ($) $ in Thousands			12 Months Ended
	Jun. 30, 2023	Apr. 21, 2023	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Definite-lived intangible assets
Weighted-Average Life (Years)			23 years	11 years
Finite-Lived Intangible Assets, Gross			$ 602,826	$ 11,488
Accumulated Amortization			21,972	6,541
Finite-Lived Intangible Assets, Net			580,854	4,947
Indefinite-lived intangible assets
Indefinite-lived intangible assets			29,200
Goodwill recognized			3,216	3,126	$ 3,313
Subtotal, Original Cost			32,441	32,351
Subtotal, Net Book Value			32,441	32,351
Balance, Original Cost			635,267	43,839
Balance, Net Book Value			613,295	37,298
Impairment of Long-Lived Assets to be Disposed of			2,700
Finished Pharmaceutical Products Segment
Indefinite-lived intangible assets
Goodwill recognized			3,216	3,126
Trademarks
Indefinite-lived intangible assets
Indefinite-lived intangible assets			$ 29,225	$ 29,225
BAQSIMI product rights
Indefinite-lived intangible assets
Estimated useful life of acquired intangible asset	24 years
Patents
Definite-lived intangible assets
Weighted-Average Life (Years)			12 years	12 years
Finite-Lived Intangible Assets, Gross			$ 486	$ 486
Accumulated Amortization			376	362
Finite-Lived Intangible Assets, Net			$ 110	$ 124
Land-Use Rights [Member]
Definite-lived intangible assets
Weighted-Average Life (Years)			39 years	39 years
Finite-Lived Intangible Assets, Gross			$ 2,540	$ 2,540
Accumulated Amortization			815	749
Finite-Lived Intangible Assets, Net			$ 1,725	$ 1,791
International Medication Systems (UK) Limited \| Acquired international product rights
Definite-lived intangible assets
Weighted-Average Life (Years)			10 years	10 years
Finite-Lived Intangible Assets, Gross			$ 8,462	$ 8,462
Accumulated Amortization			8,462	5,430
Finite-Lived Intangible Assets, Net				$ 3,032
International Medication Systems (UK) Limited \| Acquired international product rights \| Acquired international product rights
Indefinite-lived intangible assets
Impairment of Long-Lived Assets to be Disposed of			$ 2,700
BAQSIMI product rights
Indefinite-lived intangible assets
Payment to acquire assets		$ 500,000
Estimated useful life of acquired intangible asset	24 years
BAQSIMI product rights \| BAQSIMI product rights
Definite-lived intangible assets
Weighted-Average Life (Years)			24 years
Finite-Lived Intangible Assets, Gross			$ 591,338
Accumulated Amortization			12,319
Finite-Lived Intangible Assets, Net			$ 579,019

Goodwill and Intangible Asset_3

Goodwill and Intangible Assets (Summary of Changes in the Carrying Amount of Goodwill) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Goodwill and Intangible Assets
Beginning balance	$ 3,126	$ 3,313
Currency translation and other adjustments	90	(187)
Ending balance	$ 3,216	$ 3,126

Goodwill and Intangible Asset_4

Goodwill and Intangible Assets (Summary of Expected Amortization Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
2024	$ 24,718
2025	24,718
2026	24,718
2027	24,718
2028	24,718
Thereafter	457,264
Finite-Lived Intangible Assets, Net	580,854	$ 4,947
Indefinite-lived intangibles	32,441
Balance, Net Book Value	613,295	37,298
Amortization expense	12,830	954	$ 1,071
Product Rights [Member]
Amortization expense	$ 15,500	$ 900	$ 1,000

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	12 Months Ended
Inventories (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Raw materials and supplies	$ 50,082	$ 47,607
Work in process	30,822	37,090
Finished goods	24,929	18,887
Total inventory, net	105,833	103,584
Inventory adjustment to reflect net realizable value	18,800	17,200	$ 24,600
Enoxaparin
Inventory adjustment to reflect net realizable value	9,100	14,900	$ 20,700
Inventory, Firm Purchase Commitment, Loss	1,000	$ 2,700
Active Pharmaceutical Ingredient Segment
Inventory adjustment to reflect net realizable value	$ 3,600

Property, Plant, and Equipmen_2

Property, Plant, and Equipment (Summary of Property, Plant, and Equipment) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	$ 528,044	$ 458,296
Less accumulated depreciation and amortization	(245,298)	(220,030)
Total property, plant, and equipment, net	282,746	238,266
Buildings [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	168,771	130,726
Leasehold improvements [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	41,686	31,535
Land
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	7,484	7,451
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	259,484	208,068
Furniture, fixtures, and automobiles
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	31,943	29,674
Construction in progress
Property, Plant and Equipment [Line Items]
Total property, plant, and equipment	$ 18,676	$ 50,842

Property, Plant, and Equipmen_3

Property, Plant, and Equipment (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Property, Plant, and Equipment.
Depreciation expense	$ 25,205	$ 23,815	$ 22,196
Interest Costs Capitalized	$ 2,000	$ 1,400	$ 1,400

Accounts Payable and Accrued _3

Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Accounts Payable and Accrued Liabilities.
Accrued customer fees and rebates	$ 16,702	$ 14,198
Accrued payroll and related benefits	25,203	22,847
Accrued product returns, current portion	12,263	14,867
Accrued loss on firm purchase commitments	918	2,686
Accrued payments for BAQSIMI	126,090
Other accrued liabilities	12,842	9,143
Total accrued liabilities	67,928	63,741
Accounts payable	25,438	20,501
Total accounts payable and accrued liabilities	$ 93,366	$ 84,242

Debt (Schedule of Debt) (Detail

Debt (Schedule of Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Instrument
Unamortized Debt Issuance Expense	$ 13,775	$ 1,547
Equipment under Finance Leases	$ 616	$ 790
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]	Long-term debt, net of current portion and unamortized debt issuance costs	Long-term debt, net of current portion and unamortized debt issuance costs
Total debt	$ 603,790	$ 77,432
Less current portion of long-term debt and finance leases	436	3,046
Long-term debt, net of current portion and unamortized debt issuance costs	589,579	72,839
Wells Fargo Bank \| Secured debt
Debt Instrument
Unamortized Debt Issuance Expense	7,800
2029 Convertible Notes
Debt Instrument
Long Term Debt	345,000
Unamortized Debt Issuance Expense	10,300
Term Loan - paid off June 2023 \| Capital One, N.A.
Debt Instrument
Long Term Debt		68,250
Term Loan - Due June 2028 \| Wells Fargo Bank
Debt Instrument
Long Term Debt	250,000
Mortgage Payable - Due June 2027 \| East West Bank [Member]
Debt Instrument
Long Term Debt	8,016	8,188
French Government Loan 5 - Due December 2026 \| Seine-Normandie Water Agency [Member]
Debt Instrument
Long Term Debt	$ 158	$ 204

Debt (Narrative) (Details)

Debt (Narrative) (Details) $ / shares in Units, $ in Thousands			1 Months Ended				3 Months Ended		12 Months Ended
	Aug. 04, 2021 USD ($)	May 18, 2017 USD ($) building	Oct. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) D $ / shares	Jun. 30, 2023 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2023 USD ($) $ / shares	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)
Debt
Payments for repurchase of common stock									$ 58,144	$ 39,909	$ 28,873
Repayments under lines of credit											1,161
Unamortized debt issuance costs							$ 13,775		13,775	1,547
Amortization of discounts, premium, and debt issuance costs									11,399	466	$ 219
Interest rate swaps
Debt
Gains (losses) from changes in fair values of interest rate swaps									5,900	$ 5,500
2029 Convertible Notes
Debt
Debt interest rate				2%				2%
Principal amount				$ 345,000				$ 345,000
Repayment of debt				200,000
Payments for repurchase of common stock				50,000
Debt issuance costs				$ 10,800				10,800
Debt conversion ratio				15.8821
Debt principle amount converted into common stock				$ 1				$ 1
Debt conversion price per share \| $ / shares				$ 62.96				$ 62.96
Convertible debt, percentage of premium over the last reported sale price				35%
Convertible debt threshold percentage				130%
Convertible debt, threshold trading days \| D				20
Convertible debt, threshold consecutive trading days \| D				30
Threshold business days after consecutive trading period \| D				5
Threshold consecutive trading period \| D				5
Percentage of principal amount redeemed				100%
Percentage of product sale price				98%
Debt Instrument, Fair Value Disclosure							418,800		418,800
Unamortized debt issuance costs							10,300		10,300
2029 Convertible Notes \| Wells Fargo Bank
Debt
Unamortized debt issuance costs written off									3,800
Mortgage Payable - Due June 2027 \| East West Bank [Member]
Debt
Debt interest rate		4.79%
Principal amount		$ 9,000
Debt Instrument, Periodic Payment Terms, Balloon Payment to be Paid		$ 7,400
Mortgage Payable - Due June 2027 \| East West Bank [Member] \| Rancho Cucamonga, California
Debt
Number of Buildings Securing Loan \| building		1
Mortgage Payable - Due June 2027 \| East West Bank [Member] \| Chino, California
Debt
Number of Buildings Securing Loan \| building		2
Mortgage Payable - Due June 2027 \| East West Bank [Member] \| One month SOFR
Debt
Debt Instrument, Basis Spread on Variable Rate		2.60%
Line of Credit - Due October 2026 \| China Merchant Bank
Debt
Draw down period			36 months			36 months
Maximum borrowing capacity			$ 4,100			$ 14,600
Line of credit \| Capital One, N.A.
Debt
Maximum borrowing capacity	$ 140,000
Secured debt \| Capital One, N.A.
Debt
Borrowings	$ 70,000
Secured debt \| Wells Fargo Bank
Debt
Principal amount					$ 500,000
Repayment of debt							50,000		250,000
Debt issuance costs							14,300		14,300
Borrowings							250,000		250,000
Notional Amount					250,000
Repayments under lines of credit					125,000
Unamortized debt issuance costs							$ 7,800		7,800
Amortization of discounts, premium, and debt issuance costs									3,000
Secured debt \| Wells Fargo Bank \| In the first year
Debt
Debt Instrument, Annual Principal Payment					12,500
Secured debt \| Wells Fargo Bank \| Starting in the Second year
Debt
Debt Instrument, Annual Principal Payment					25,000
Secured debt \| Wells Fargo Bank \| Starting in the third year
Debt
Debt Instrument, Annual Principal Payment					$ 37,500
Secured debt \| Wells Fargo Bank \| Interest rate swaps
Debt
Debt interest rate					4.04%
Gains (losses) from changes in fair values of interest rate swaps									$ (5,400)
Secured debt \| Wells Fargo Bank \| Federal funds rate
Debt
Debt Instrument, Basis Spread on Variable Rate					0.50%
Secured debt \| Wells Fargo Bank \| Adjusted term SOFR rate
Debt
Debt Instrument, Basis Spread on Variable Rate					2.25%
Debt instrument interest rate floor, percentage					0%
Secured debt \| Wells Fargo Bank \| SOFR rate
Debt
Debt Instrument, Basis Spread on Variable Rate					1.25%
Secured debt \| Wells Fargo Bank \| One month SOFR
Debt
Debt Instrument, Basis Spread on Variable Rate					1%
Secured debt \| 2029 Convertible Notes \| Wells Fargo Bank
Debt
Repayment of debt								$ 200,000
Revolving Credit Facility \| Wells Fargo Bank
Debt
Maximum borrowing capacity					$ 200,000
Minimum \| Secured debt \| Capital One, N.A.
Debt
Debt Instrument, Basis Spread on Variable Rate	0.50%
Minimum \| Secured debt \| Wells Fargo Bank \| Base rate
Debt
Debt Instrument, Basis Spread on Variable Rate					0.50%
Minimum \| Secured debt \| Wells Fargo Bank \| Adjusted term SOFR rate
Debt
Debt Instrument, Basis Spread on Variable Rate					1.50%
Maximum \| Secured debt \| Capital One, N.A.
Debt
Debt Instrument, Basis Spread on Variable Rate	2.50%
Maximum \| Secured debt \| Wells Fargo Bank \| Base rate
Debt
Debt Instrument, Basis Spread on Variable Rate					1.50%
Maximum \| Secured debt \| Wells Fargo Bank \| Adjusted term SOFR rate
Debt
Debt Instrument, Basis Spread on Variable Rate					2.50%

Debt (Long-Term Debt Maturities

Debt (Long-Term Debt Maturities) (Details) $ in Thousands	Dec. 31, 2023 USD ($)
Debt
2024	$ 234
2025	245
2026	254
2027	7,441
2028	250,000
Thereafter	345,000
Total long-term Debt	$ 603,174

Income Taxes (Summary of Income

Income Taxes (Summary of Income (Loss) Before Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income (loss) before income taxes:
United States	$ 181,922	$ 127,204	$ 86,236
Foreign	(10,563)	(11,164)	(2,097)
Income (loss) before income taxes	171,359	116,040	84,139
Income tax provision	31,833	23,477	20,630
Income before equity in losses of unconsolidated affiliate	$ 139,526	$ 92,563	$ 63,509
Income tax provision as a percentage of income before income taxes	18.60%	20.20%	24.50%
Deferred tax asset	$ 111,618	$ 92,584

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Tax Credit Carryforward [Line Items]
Federal income tax rate	21%	21%	21%
Cumulative excess benefits of stock compensation established	$ 5,464	$ 5,208
Deferred Tax Assets, Valuation Allowance	20,495	19,700
AFP
Tax Credit Carryforward [Line Items]
Deferred Tax Assets, Valuation Allowance	19,000	$ 18,900
California Franchise Tax Board [Member] \| Research and Development Tax Credit
Tax Credit Carryforward [Line Items]
Tax Credit Carryforward, Amount	20,200
Foreign Tax Authority \| FRANCE
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards	76,200
Foreign Tax Authority \| UNITED KINGDOM
Tax Credit Carryforward [Line Items]
Operating Loss Carryforwards	$ 2,800

Income Taxes (Summary of Provis

Income Taxes (Summary of Provision (Benefit) for Income Taxes) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Current provision (benefit):
Federal	$ 42,689	$ 37,626	$ 14,088
State	1,912	732	1,182
Foreign	1,089	998	1,676
Total current provision (benefit)	45,690	39,356	16,946
Deferred provision (benefit):
Federal	(13,134)	(16,119)	2,657
State	1,537	816	110
Foreign	(2,260)	(576)	917
Total deferred provision (benefit)	(13,857)	(15,879)	3,684
Total provision (benefit) for income taxes	$ 31,833	$ 23,477	$ 20,630

Income Taxes (Reconciliation of

Income Taxes (Reconciliation of the Statutory Federal Income Tax Rate to the Effective Tax Rate) (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of the statutory federal income tax rate to the Companys effective rate:
Statutory federal income tax (benefit)	21%	21%	21%
State tax expense, net of federal tax benefit	1.60%	1.10%	1.20%
Foreign tax rate differences	(0.10%)	(0.30%)	(2.00%)
Foreign valuation allowance	0.10%	2.60%	5.50%
Research and development credits	(4.20%)	(3.10%)	(3.20%)
Share-based compensation	(3.20%)	(3.50%)	(0.20%)
Executive compensation	2.40%	2.30%	2.30%
Employee-related expenses		0.20%	0.10%
Intercompany transfer of assets other than inventory	0.60%
Other	0.40%	(0.10%)	(0.20%)
Effective tax rate (benefit)	18.60%	20.20%	24.50%

Income Taxes (Schedule of Defer

Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Research and development credits	$ 12,759	$ 15,418
Net operating loss carryforward	20,156	20,019
Inventory capitalization and reserve	12,381	9,598
Share-based compensation	5,464	5,208
Operating leases	8,360	6,684
Accrued expenses	5,970	4,956
Accrued chargebacks	5,441	5,125
Product return allowance	4,927	5,464
Intangibles	2,124	2,124
Research and development capitalization	34,036	17,988
Total deferred tax assets	111,618	92,584
Deferred tax liabilities:
Depreciation/amortization	21,630	13,272
Intangibles	4,367	8,564
Operating leases	8,037	6,398
Federal impact of state deferred taxes	3,577	3,800
Other	260	2,467
Total deferred tax liabilities	37,871	34,501
Valuation allowance	(20,495)	(19,700)
Net deferred tax assets	$ 53,252	$ 38,383

Income Taxes (Reconciliation _2

Income Taxes (Reconciliation of Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at the beginning of the year	$ 12,895	$ 11,796	$ 10,053
Deductions based on tax positions related to prior years		(41)
Additions based on tax positions related to the current year	2,074	1,643	1,754
Deductions based on statute of limitations	(2,476)	(503)	(11)
Balance at the end of the year	$ 12,493	$ 12,895	$ 11,796

Income Taxes (Uncertain Income

Income Taxes (Uncertain Income Tax Positions - Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Income Tax Contingency [Line Items]
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	$ 11.7	$ 12.2
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	$ 1	$ 0.8	$ 0.5
Domestic Tax Authority [Member] \| Earliest Tax Year [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2020
Domestic Tax Authority [Member] \| Latest Tax Year [Member] \| Internal Revenue Service (IRS) [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2022
State and Local Jurisdiction [Member] \| Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2019
State and Local Jurisdiction [Member] \| Earliest Tax Year [Member] \| California Franchise Tax Board [Member]
Income Tax Contingency [Line Items]
Income Tax Examination, Year under Examination	2019
State and Local Jurisdiction [Member] \| Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2022
State and Local Jurisdiction [Member] \| Latest Tax Year [Member] \| California Franchise Tax Board [Member]
Income Tax Contingency [Line Items]
Income Tax Examination, Year under Examination	2021
Foreign Tax Authority \| Earliest Tax Year [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2013
Foreign Tax Authority \| Latest Tax Year [Member]
Income Tax Contingency [Line Items]
Open Tax Year	2022

Stockholders' Equity (Share Buy

Stockholders' Equity (Share Buyback Program) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Equity, Class of Treasury Stock [Line Items]
Stock buyback program, authorized amount	$ 285,000
Treasury Stock, Value, Acquired, Cost Method	$ 58,144	$ 39,909	$ 28,873
November 2014 Share Repurchase Plan
Equity, Class of Treasury Stock [Line Items]
Treasury Stock, Shares, Acquired (in Shares)	1,338,757	1,335,528	1,477,305
Treasury Stock, Value, Acquired, Cost Method	$ 58,100	$ 39,900	$ 28,900

Stockholders' Equity (The 2015

Stockholders' Equity (The 2015 Equity Incentive Plan) (Details) - shares	1 Months Ended	12 Months Ended
	Jan. 31, 2024	Dec. 31, 2023	Mar. 18, 2015
The 2015 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in Shares)		6,777,943	5,300,296
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)			5,000,000
Equity Incentive Plan, Term		10 years
Share Based Compensation Arrangement By Share Based Payment Award Potential Number of Additional Shares Authorized (in Shares)		3,000,000
Share Based Compensation Arrangement by Share Based Payment Award Potential Annual Increase in Shares, Percentage		2.50%
The 2015 Equity Incentive Plan [Member] \| Minimum \| Shares subject to a minimum vesting requirement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of shares awarded subject to a minimum vesting requirement		95%
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		1 year
The 2015 Equity Incentive Plan [Member] \| Subsequent event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	1,201,722
Amended and Restated 2005 Equity Plan \| Existing Employees [Member] \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		3 years
Amended and Restated 2005 Equity Plan \| Existing Employees [Member] \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		5 years
Amended and Restated 2005 Equity Plan \| New Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		4 years
Amended and Restated 2005 Equity Plan \| Board of Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period		1 year

Stockholders' Equity (2014 Empl

Stockholders' Equity (2014 Employee Stock Purchase Plan) (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation		$ 20,242	$ 17,860	$ 18,687
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Purchase Plan, Offering Duration, Maximum	27 months
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date	85%
Stock Issued During Period, Shares, Employee Stock Purchase Plans (in Shares)		1,192,134
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant (in Shares)		807,866
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in Shares)	2,000,000
Allocated share based compensation		$ 1,100	$ 900	$ 700

Stockholders' Equity (Key Assum

Stockholders' Equity (Key Assumptions Used in Determining Fair Value of Options Granted) (Details)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stockholders' Equity
Average overall forfeiture rate	7%	7%	6%
Average volatility	41.40%	41%	42.10%
Average risk-free interest rate	4.10%	2.30%	1.20%
Weighted-average expected life in years	6 years 2 months 12 days	6 years 1 month 6 days	6 years 1 month 6 days

Stockholders' Equity (Summary o

Stockholders' Equity (Summary of Option Activity) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Options
Outstanding Options, Beginning of period	7,929,150
Options granted	759,820
Options exercised	(920,817)
Options forfeited	(5,312)
Options expired	(543)
Outstanding Options, End of period	7,762,298	7,929,150
Exercisable at the end of period	5,685,943
Vested and expected to vest, at the end of period	7,601,023
Weighted-Average Exercise Price
Outstanding Exercise Price (in dollars per share)	$ 17.66
Options granted (in dollars per share)	35.84
Options exercised (in dollars per share)	15.40
Options forfeited (in dollars per share)	30.82
Options expired (in dollars per share)	16.25
Outstanding Exercise Price (in dollars per share)	19.70	$ 17.66
Exercisable at the end of period (in dollars per share)	16.55
Vested and expected to vest at end of period (in dollars per share)	$ 19.46
Additional Disclosures
Contractual term	4 years 6 months 14 days
Outstanding Intrinsic Value	$ 327,155
Exercisable remaining contractual term (in Years)	3 years 3 months
Exercisable aggregate intrinsic value	$ 257,560
Allocated share based compensation	20,242	$ 17,860	$ 18,687
Vested and expected to vest aggregate intrinsic value	$ 322,203
Vested and expected to vest weighted average remaining contractual term	4 years 5 months 15 days
The 2015 Plan and 2005 Plan [Member] \| Minimum
Additional Disclosures
Contractual term	5 years
Vesting term	3 years
The 2015 Plan and 2005 Plan [Member] \| Maximum
Additional Disclosures
Contractual term	10 years
Vesting term	5 years
Employee Stock Option
Additional Disclosures
Allocated share based compensation	$ 9,600	$ 8,500	$ 8,000

Stockholders' Equity (Informati

Stockholders' Equity (Information Relating to Option Grants and Exercises) (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Stockholders' Equity
Weighted-average grant date fair value (in Dollars per share)	$ 16.76	$ 14.75	$ 7.62
Intrinsic value of options exercised	$ 29,918	$ 21,279	$ 7,906
Cash received from options exercised	14,172	19,202	16,757
Total fair value of the options vested during the period	$ 8,890	$ 8,174	$ 8,177

Stockholders' Equity (Summary_2

Stockholders' Equity (Summary of Nonvested Options) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Options
Nonvested at beginning of period	2,378,453
Options granted	759,820
Options vested	(1,056,606)
Options forfeited	(5,312)
Nonvested at end of period	2,076,355	2,378,453
Weighted-Average Grant Date Fair Value
Nonvested at beginning of period (in dollars per share)	$ 9.48
Options granted (in dollars per share)	16.76	$ 14.75	$ 7.62
Options vested (in dollars per share)	8.41
Options forfeited (in dollars per share)	13.94
Nonvested at end of period (in dollars per share)	$ 12.68	$ 9.48
Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options	$ 17.1
Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 6 months

Stockholders' Equity (Restricte

Stockholders' Equity (Restricted Stock Units) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 20,242	$ 17,860	$ 18,687
Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 6 months
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	5 years
Allocated share based compensation	$ 9,500	$ 8,400	$ 8,100
Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	2 years 6 months
Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock Units, Number of Shares of Common Stock Per Award (in Shares)	1
Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Share-based Awards Other than Options	$ 18,100
Maximum \| Amended and Restated 2005 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period	10 years
Board of Directors \| Amended and Restated 2005 Equity Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	1 year

Stockholders' Equity (Informa_2

Stockholders' Equity (Information Relating to RSU Grants and Deliveries) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Total RSUs outstanding at the beginning of the period	1,007,052
RSUs granted	356,176
RSUs forfeited	(2,368)
RSUs vested	(440,484)
Total RSUs outstanding at the end of the period	920,376
Total Fair Market Value of RSUs Issued
RSUs granted (in Dollars) \| $	$ 12,725
Restricted stock units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Stock surrendered to fulfill tax withholding obligations	168,067

Stockholders' Equity (The 2018

Stockholders' Equity (The 2018 ANP Equity Incentive Plan) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2021	Sep. 30, 2021	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jun. 30, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding			7,762,298	7,929,150
Number of vested options			1,056,606
Number of unvested options			2,076,355	2,378,453
Vested options cancelled			5,312
Unvested options cancelled			5,312
Contractual term			4 years 6 months 14 days
Compensation cost not yet recognized			$ 17,100
Allocated share based compensation			20,242	$ 17,860	$ 18,687
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation			$ 12,269	$ 11,180	12,622
The 2018 ANP Equity Incentive Plan Termination
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan modification, share-based compensation expense					2,300
Compensation cost not yet recognized					500
The 2018 ANP Equity Incentive Plan Termination \| General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Plan modification, share-based compensation expense					1,800
Employee [Member] \| The 2018 ANP Equity Incentive Plan Termination
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding		4,091,080
Number of vested options		1,944,771
Number of unvested options		2,146,309
Options fair value		$ 800
Options cancelled	927,800
Vested options cancelled	56,925
Unvested options cancelled	870,875
The 2018 ANP Equity Incentive Plan \| Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Contractual term	10 years
Allocated share based compensation					$ 500
The 2018 ANP Equity Incentive Plan \| Employee [Member] \| The 2018 ANP Equity Incentive Plan Termination
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options outstanding						5,018,880
The 2015 Equity Incentive Plan [Member] \| Employee [Member] \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
The 2015 Equity Incentive Plan [Member] \| Employee [Member] \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	2 years

Stockholders' Equity (Share-Bas

Stockholders' Equity (Share-Based Compensation Expense Included in the Statement of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 20,242	$ 17,860	$ 18,687
Cost Of Revenues [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	4,891	4,179	3,778
Selling, Distribution And Marketing [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	870	726	596
General and administrative expenses
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	12,269	11,180	12,622
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share based compensation	$ 2,212	$ 1,775	$ 1,691

Employee Benefits (Details)

Employee Benefits (Details) - USD ($) $ in Millions	12 Months Ended
Employee Benefits (Details) - USD ($) $ in Millions	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Employee Benefits
Defined Contribution Plan, Employer Matching Contribution, Percent of Match	50%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay	6%
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 2.3	$ 2.2	$ 2
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	3.25%	3.75%
Defined Benefit Plan, Benefit Obligation	$ 2.6	$ 2.2
Deferred compensation plan assets	6.8	4.5
Deferred compensation plan liabilities	$ 7.1	$ 4.6

Commitments and Contingencies_2

Commitments and Contingencies (Lease Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Lessee, Lease, Description [Line Items]
Right-of-use assets	$ 32,333	$ 25,554
Lease obligations	33,627
Operating lease cost	5,267	4,709	$ 4,328
Short-term lease costs	332	300	518
Amortization of right-of-use assets	189	237	384
Interest on lease liabilities	45	26	26
Total financed lease cost	234	263	410
Total lease costs	$ 5,833	$ 5,272	$ 5,256
Minimum
Lessee, Lease, Description [Line Items]
Lease renewal term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lease renewal term	6 years

Commitments and Contingencies_3

Commitments and Contingencies (Lease Cash Flow Information) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Commitments and Contingencies
Operating cash flows paid for operating Leases	$ 5,106	$ 4,329	$ 4,446
Operating cash flows paid for finance leases	40	18	25
Financing cash flows paid for finance leases	154	233	310
Right-of use assets obtained in exchange for lease obligations: Operating leases	$ 10,521	2,166	11,041
Right-of use assets obtained in exchange for lease obligations: Finance leases		$ 642	$ 110
Weighted-average remaining lease term (years), Operating leases	7 years 8 months 12 days	8 years 8 months 12 days	9 years 6 months
Weighted-average remaining lease term (years), Finance leases	3 years 4 months 24 days	4 years 3 months 18 days	2 years 4 months 24 days
Weighted-average discount rate, Operating leases	5.50%	4.40%	4.50%
Weighted-average discount rate, Finance leases	6.70%	6.70%	5.20%

Commitments and Contingencies_4

Commitments and Contingencies (Future Minimum Rental Payments) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Operating Leases
2024	$ 5,611
2025	5,536
2026	5,586
2027	5,359
2028	4,605
Thereafter	14,805
Total lease payments	41,502
Less: interest	7,875
Total	33,627
Finance Leases
2024	236
2025	190
2026	158
2027	104
Total lease payments	688
Less: interest	72
Total	616	$ 790
Total
2024	5,847
2025	5,726
2026	5,744
2027	5,463
2028	4,605
Thereafter	14,805
Total lease payments	42,190
Less: interest	7,947
Total	$ 34,243

Commitments and Contingencies_5

Commitments and Contingencies (Purchase Commitments) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Commitments to Purchase Equipment and Raw Materials [Member]
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Long-term Purchase Commitment, Amount	$ 93.3

Related-Party Transactions (Det

Related-Party Transactions (Details) - USD ($) $ in Thousands	1 Months Ended			12 Months Ended
	Mar. 31, 2023	Nov. 30, 2022	Jul. 31, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Related Party Transaction [Line Items]
Total net revenues				$ 644,395	$ 498,987	$ 437,768
Hanxin
Related Party Transaction [Line Items]
Payment to related party				$ 1,600	600
Ownership after transaction				11.50%
Related Party Transaction, Amounts of Transaction	$ 500		$ 2,200
Letop
Related Party Transaction [Line Items]
Receivables from Hanxin				$ 0
ANP \| Hanxin
Related Party Transaction [Line Items]
Total net revenues				100	400
ANP \| Letop
Related Party Transaction [Line Items]
Payment to related party				700	$ 200
Related Party Transaction, Due from (to) Related Party, Current				$ 0
Related Party Transaction, Amounts of Transaction		$ 1,500

Litigation (Details)

Litigation (Details) - Settled Litigation [Member] - USD ($) $ in Millions				1 Months Ended	3 Months Ended		12 Months Ended
	Jun. 30, 2021	May 03, 2021	Nov. 13, 2020	May 31, 2021	Dec. 31, 2021	Jun. 30, 2021	Dec. 31, 2022	Dec. 31, 2021
Loss Contingencies [Line Items]
Litigation Settlement, amount paid to the Company					$ 2.7
Amphastar Pharmaceuticals, Inc. Vs Aventis Pharma, SA
Loss Contingencies [Line Items]
Litigation Settlement, Amount	$ 14.5	$ 4.4	$ 12.1	$ 17.2
Costs and expenses			$ 0.7
Estimated Litigation Liability					$ 12.8			$ 12.8
Litigation settlement accrual amount increase						$ 1.7
Employee Litigation
Loss Contingencies [Line Items]
Litigation Settlement, Amount								$ 1
Amphastar Pharmaceuticals vs Astellas-Gilead \| Astellas-Gilead
Loss Contingencies [Line Items]
Litigation Settlement, amount paid to the Company							$ 5.4

Subsequent Events (Details)

Subsequent Events (Details) $ in Millions	Jan. 31, 2024 USD ($)
Subsequent event \| Line of credit \| ICBC Bank \| Line of Credit Due June 2033
Subsequent Event [Line Items]
Maximum borrowing capacity	$ 40

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pay vs Performance Disclosure
Net Income (Loss)	$ 137,545	$ 91,386	$ 62,116

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2023 shares
Trading Arrangements, by Individual
Non-Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Terminated	false
Jacob Liawatidewi
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	On November 17, 2023, Jacob Liawatidewi, our Executive Vice President of Sales and Marketing and Corporate Administration Center, President of Amphastar France Pharmaceuticals, S.A.S., Corporate Secretary, and Director, adopted a Rule 10b5-1 trading arrangement providing for the sale from time to time of an aggregate of up to 20,533 shares of our common stock. The trading arrangement is intended to satisfy the affirmative defense in Rule 10b5-1(c). The duration of the trading arrangement is until April 1, 2025, or earlier if all transactions under the trading arrangement are completed.
Name	Jacob Liawatidewi
Title	Executive Vice President of Sales and Marketing and Corporate Administration Center, President of Amphastar France Pharmaceuticals, S.A.S., Corporate Secretary, and Director
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	November 17, 2023
Aggregate Available	20,533
Expiration Date	April 1, 2025
Rong Zhou
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	On December 14, 2023, Rong Zhou, our Senior Executive Vice President of Production and President of Amphastar Nanjing Pharmaceuticals, Co., Ltd., adopted a Rule 10b5-1 trading arrangement providing for the sale from time to time of an aggregate of up to 13,893 shares of our common stock. The trading arrangement is intended to satisfy the affirmative defense in Rule 10b5-1(c). The duration of the trading arrangement is until May 17, 2024, or earlier if all transactions under the trading arrangement are completed.
Name	Rong Zhou
Title	Senior Executive Vice President of Production and President of Amphastar Nanjing Pharmaceuticals, Co., Ltd.
Rule 10b5-1 Arrangement Adopted	true
Adoption Date	December 14, 2023
Aggregate Available	13,893
Expiration Date	May 17, 2024