AMOXAPINE Drug Patent Profile

When do Amoxapine patents expire, and when can generic versions of Amoxapine launch?

Amoxapine is a drug marketed by Chartwell Rx, Watson Labs, and Watson Pharms Teva. and is included in six NDAs.

The generic ingredient in AMOXAPINE is amoxapine. There is one drug master file entry for this compound. Two suppliers are listed for this compound. Additional details are available on the amoxapine profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Amoxapine

A generic version of AMOXAPINE was approved as amoxapine by CHARTWELL RX on June 28^th, 1991.

Summary for AMOXAPINE

US Patents:	0
Applicants:	3
NDAs:	6
Finished Product Suppliers / Packagers:	2
Raw Ingredient (Bulk) Api Vendors:	1
Clinical Trials:	4
Patent Applications:	4,837
Drug Prices:	Drug price information for AMOXAPINE
DailyMed Link:	AMOXAPINE at DailyMed

See drug prices for AMOXAPINE

Recent Clinical Trials for AMOXAPINE

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
Fundação de Amparo à Pesquisa do Estado de São Paulo	Phase 4
Federal University of São Paulo	Phase 4
Alexza Pharmaceuticals, Inc.	Phase 1

See all AMOXAPINE clinical trials

Pharmacology for AMOXAPINE

Drug Class

Tricyclic Antidepressant

Medical Subject Heading (MeSH) Categories for AMOXAPINE

Adrenergic Uptake Inhibitors

Antidepressive Agents, Second-Generation

Dopamine Antagonists

Neurotransmitter Uptake Inhibitors

Serotonin Uptake Inhibitors

Anatomical Therapeutic Chemical (ATC) Classes for AMOXAPINE

N06AA	Non-selective monoamine reuptake inhibitors
N06A	ANTIDEPRESSANTS
N06	PSYCHOANALEPTICS
N	Nervous system

US Patents and Regulatory Information for AMOXAPINE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Chartwell Rx	AMOXAPINE	amoxapine	TABLET;ORAL	072879-002	Jun 28, 1991	AB	RX	No	No
Watson Labs	AMOXAPINE	amoxapine	TABLET;ORAL	072691-004	Aug 28, 1992	AB	RX	No	No
Chartwell Rx	AMOXAPINE	amoxapine	TABLET;ORAL	072879-001	Jun 28, 1991	AB	RX	No	No

Amoxapine Market Dynamics, Patent Status, Generic Competition, and Financial Trajectory

Last updated: September 9, 2026

Amoxapine is a mature, low-volume generic antidepressant with no meaningful remaining patent or regulatory exclusivity in the United States. The drug is sold as immediate-release tablets in 25 mg, 50 mg, 100 mg, and 150 mg strengths. Its commercial market is constrained by competition from newer antidepressants, limited manufacturer participation, safety monitoring requirements, and low prescribing volume. Public companies do not separately report amoxapine revenue, so the drug’s financial trajectory is best characterized as stable-to-declining within a small generic niche rather than as a growth market.

What is amoxapine and how is it used?

Amoxapine is a tetracyclic antidepressant related pharmacologically to the dibenzoxazepine class. It is indicated for the treatment of depression, including depression accompanied by anxiety or psychotic features, under the U.S. prescribing information. The drug has norepinephrine and serotonin reuptake activity and dopaminergic antagonism that contributes to its adverse-effect profile.

The U.S. label identifies the following tablet strengths:

Strength	Dosage form	U.S. market status
25 mg	Immediate-release tablet	Generic
50 mg	Immediate-release tablet	Generic
100 mg	Immediate-release tablet	Generic
150 mg	Immediate-release tablet	Generic

Amoxapine is generally used when clinicians have a specific reason to select an older antidepressant. Selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, atypical antidepressants, and other modern therapies have reduced demand for tetracyclic antidepressants.

The prescribing information carries the class boxed warning for increased suicidal thoughts and behaviors in pediatric, adolescent, and young adult patients treated with antidepressants. The label also warns about tardive dyskinesia, neuroleptic malignant syndrome, seizures, orthostatic hypotension, cardiovascular effects, and other risks associated with amoxapine’s pharmacology (DailyMed, n.d.).

When did amoxapine lose market exclusivity?

Amoxapine lost meaningful commercial exclusivity decades ago. The original U.S. product, Asendin, was introduced in the early 1980s, and generic versions have been available for many years. Any original patent and new-drug exclusivity associated with the product have expired.

Event	Approximate timing
Original U.S. approval and commercial introduction	Early 1980s
Brand product	Asendin
Generic availability	Established for decades
Current patent exclusivity	None of commercial significance
Current regulatory exclusivity	None of commercial significance
Current market structure	Generic immediate-release tablets

Because amoxapine is an old small-molecule drug, the principal commercial barriers are no longer patent rights. They are manufacturing economics, procurement contracts, active pharmaceutical ingredient availability, regulatory compliance, and the limited size of the prescriber and patient base.

What patents protect amoxapine?

No active U.S. composition-of-matter or formulation patent is known to provide meaningful market protection for generic amoxapine. The original active ingredient and conventional tablet formulation are long past the standard U.S. patent term.

Patent estate assessment

Patent category	Commercial relevance
Composition of matter	Expired
Original formulation	Expired
Immediate-release tablet	No meaningful exclusivity
Method of use	No material current exclusivity identified
Manufacturing process	Possible process know-how, but not a market-blocking barrier
Pediatric exclusivity	Not commercially relevant
Orphan-drug exclusivity	Not applicable
Biosimilar exclusivity	Not applicable

The absence of a meaningful patent estate means a new generic applicant would generally compete through an abbreviated new drug application rather than through a patent license or negotiated entry agreement.

What is the Orange Book status of amoxapine?

Amoxapine is a conventional small-molecule generic drug, not a biologic. Its relevant FDA pathway is an abbreviated new drug application, or ANDA, rather than a biosimilar application.

The FDA Orange Book identifies approved drug products and, where applicable, patent and exclusivity information. For a long-established generic such as amoxapine, the commercially relevant Orange Book question is whether an active listed patent or exclusivity period blocks additional ANDA approvals. No such current exclusivity is central to the market position of amoxapine (U.S. Food and Drug Administration [FDA], n.d.-a).

Orange Book status should be distinguished from commercial availability. A drug can remain FDA-approved while being intermittently unavailable, manufactured by few suppliers, or absent from major retail pharmacies.

How many patents cover amoxapine?

There is no meaningful active U.S. patent cluster covering the marketed amoxapine tablet. Historical patent records may contain expired claims relating to the molecule, pharmaceutical compositions, or manufacturing methods, but expired patents do not restrict generic launch.

The practical freedom-to-operate position is therefore favorable for generic manufacturers. A company seeking to market amoxapine would face ordinary regulatory and technical requirements rather than a dense patent thicket.

Potential technical barriers include:

• Demonstrating pharmaceutical equivalence to the reference product.
• Maintaining consistent tablet potency and dissolution.
• Sourcing qualified amoxapine active pharmaceutical ingredient.
• Supporting stability data for all marketed strengths.
• Maintaining compliant manufacturing and quality systems.
• Managing low annual production volumes without excessive unit costs.

These barriers can matter financially even when patent barriers do not.

Which companies are challenging amoxapine patents?

No significant current Paragraph IV campaign is associated with amoxapine. The drug’s market is too mature and too small to support the type of litigation commonly seen with high-revenue branded drugs.

Paragraph IV risk

A Paragraph IV certification is used when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or will not be infringed. Amoxapine has no commercially important active patent position that would ordinarily justify a high-value Paragraph IV strategy.

The likely entry pathway for a new supplier would be:

1. File an ANDA for one or more tablet strengths.
2. Address reference-product bioequivalence and product quality.
3. Certify against any listed patent or exclusivity entry.
4. Obtain FDA approval.
5. Compete through wholesalers, hospitals, pharmacies, and government purchasing channels.

Litigation risk is therefore low compared with newer antidepressants and branded CNS products.

What formulation patents protect amoxapine?

The marketed U.S. product is an immediate-release tablet. No commercially important extended-release, transdermal, injectable, long-acting, or other protected formulation has established a separate amoxapine market in the United States.

Formulation	Market position	Patent relevance
Immediate-release tablet	Established generic product	No meaningful active protection
Extended-release tablet	No major U.S. commercial segment identified	No material market-blocking estate
Transdermal product	No established U.S. product	Not commercially relevant
Injectable product	No established U.S. product	Not commercially relevant
Combination product	No established U.S. product	Not commercially relevant

A company could theoretically develop a differentiated formulation, but the small patient population would make clinical, regulatory, and commercialization costs difficult to justify. Any reformulation would also need to demonstrate a clinically credible advantage over inexpensive generic tablets.

What is the FDA regulatory status of amoxapine?

Amoxapine remains an FDA-approved prescription antidepressant in tablet form. Its regulatory status is distinct from its commercial visibility. The drug is not a withdrawn product simply because the original brand has disappeared from routine retail promotion.

The principal FDA-related commercial issues are:

• Continued availability of approved generic applications.
• Compliance with current good manufacturing practices.
• Labeling for suicidality and serious psychiatric and neurologic adverse events.
• Supply continuity for all tablet strengths.
• Pharmacovigilance for an older CNS medicine.

The product is not eligible for biosimilar competition because biosimilar applications apply to biological products, not conventional synthetic antidepressants.

How strong is the amoxapine patent estate?

The patent estate is weak from a branded-product perspective and permissive from a generic-entry perspective.

Factor	Assessment
Remaining composition patent	None of material commercial significance
Remaining formulation patent	None of material commercial significance
Method-of-use protection	No meaningful current barrier identified
Patent litigation exposure	Low
Generic entry freedom	High
Manufacturing complexity	Low to moderate
Supply-chain vulnerability	Moderate because of limited demand and supplier participation
Pricing power	Low
Brand defense potential	Negligible

Amoxapine’s defensibility does not come from intellectual property. A supplier’s advantage would more likely arise from reliable inventory, wholesaler relationships, regulatory execution, or a lower-cost manufacturing base.

What is the financial trajectory of amoxapine?

Amoxapine does not have a separately reported public revenue stream comparable to major branded antidepressants. Generic manufacturers typically report portfolios in aggregate, and amoxapine sales are not normally broken out in annual reports.

The financial trajectory has four defining characteristics:

Low and declining prescription demand

Prescribing has shifted toward SSRIs, SNRIs, atypical antidepressants, and other agents with broader contemporary use. Amoxapine remains clinically relevant for selected patients but is not a first-line volume product in most treatment settings.

Low average selling prices

Generic tablet pricing is constrained by therapeutic substitution and pharmacy benefit purchasing. The product has little ability to sustain premium pricing absent a shortage or temporary supplier withdrawal.

Limited supplier economics

A small market can support only a limited number of manufacturers. The result is a structurally thin market in which an individual supplier may gain temporary share without creating a large absolute revenue opportunity.

Potential episodic price increases

Older generic drugs can experience price volatility when a supplier exits, an API source is disrupted, or a manufacturing issue affects inventory. Such increases tend to reflect supply scarcity rather than durable demand growth.

A useful commercial model is:

Revenue driver	Expected effect on amoxapine
Higher depression prevalence	Limited positive effect
Preference for newer antidepressants	Negative
Generic price competition	Negative
Supplier exit	Short-term positive for remaining suppliers
Manufacturing disruption	Negative for volume, potentially positive for price
New formulation investment	Low probability because of small market
Brand relaunch	Commercially unattractive
Government purchasing	Supports baseline demand but limits pricing

What generic entry risks exist for amoxapine?

Generic entry risk is high in legal terms but moderate in commercial terms. A new entrant could face little patent opposition, yet still determine that the market is too small to justify development and launch expenses.

The main risks to existing suppliers are:

• Approval of an additional ANDA.
• Loss of a hospital or wholesaler contract.
• Substitution by another low-cost antidepressant.
• Reimbursement changes.
• Price reductions by larger generic manufacturers.
• Retail pharmacy delisting due to low turnover.

The main risks to patients and purchasers are different. A thin supplier base can increase the probability of intermittent shortages, backorders, or uneven availability by strength.

How does amoxapine compare with competing antidepressants?

Drug class	Examples	Commercial position versus amoxapine
SSRI	Sertraline, fluoxetine, escitalopram	Much broader prescribing and stronger generic volume
SNRI	Venlafaxine, duloxetine	Higher contemporary use and broader indications
Atypical antidepressant	Bupropion, mirtazapine	Stronger market relevance
Tetracyclic	Amoxapine, maprotiline	Older, lower-volume niche
Tricyclic	Amitriptyline, nortriptyline	Larger legacy use in some indications
Newer branded agents	Vortioxetine, vilazodone	Higher pricing but protected by more recent commercial strategies

Amoxapine can compete on low acquisition cost, but it does not compete effectively on convenience, tolerability, prescriber familiarity, or promotional support.

What licensing deals affect amoxapine?

No major current licensing transaction or strategic alliance is associated with amoxapine. The drug has no active innovation platform, branded delivery technology, or high-value patent estate likely to attract pharmaceutical licensing interest.

A transaction involving amoxapine would more likely be an asset purchase, ANDA transfer, contract-manufacturing arrangement, or portfolio acquisition than a royalty-bearing innovation license. The economic value would be tied to approved manufacturing capacity and supply contracts rather than future exclusivity.

What patent litigation affects amoxapine?

No material recent U.S. patent litigation is associated with the marketed amoxapine tablet. The absence of litigation is consistent with the drug’s low revenue base, expired exclusivity, and generic market structure.

Any future dispute would more likely concern:

• ANDA ownership or transfer.
• Manufacturing quality.
• Supply contracts.
• False advertising or product labeling.
• Antitrust conduct in generic distribution.
• Intellectual property associated with a new formulation, if one were developed.

A conventional amoxapine tablet does not present the economic profile that typically supports extended Hatch-Waxman litigation.

What geographic markets are relevant to amoxapine?

The United States is a mature generic market with limited growth potential. International availability varies by country, and product registration, reimbursement, and manufacturer participation may differ substantially.

Geography	Commercial assessment
United States	Mature generic market; low growth
European markets	Availability varies by country and reimbursement system
Canada	Generic availability may be limited by supplier participation
Emerging markets	Potentially broader use where older antidepressants remain common
Low-income markets	Price-sensitive, with procurement-driven demand

Geographic expansion would require country-specific registrations, local pharmacovigilance, packaging, distribution, and reimbursement access. These costs could exceed the value of incremental sales in many jurisdictions.

What manufacturing and intellectual property barriers exist?

Manufacturing is more important than intellectual property. Amoxapine is a synthetic small molecule, and its conventional tablet does not require biologic production, sterile fill-finish, or complex delivery-device technology. The technical process is therefore less challenging than for biologics or modified-release products.

The principal barriers are economic:

• Low production scale.
• Minimum batch sizes.
• API procurement.
• Product testing and release costs.
• Inventory carrying costs across four strengths.
• Limited ability to recover regulatory overhead through price.
• Risk that a supplier withdrawal creates shortage exposure.

For purchasers, supply reliability may be more valuable than nominal unit price. For manufacturers, the strongest competitive position is likely to come from dependable supply and efficient portfolio management.

Key Takeaways

• Amoxapine is an old, FDA-approved generic antidepressant marketed primarily as immediate-release tablets.
• The original Asendin-era exclusivity has expired, and no meaningful active U.S. patent estate protects the conventional product.
• No major current Paragraph IV campaign, licensing deal, or patent litigation defines the market.
• Biosimilar competition is irrelevant because amoxapine is a synthetic small molecule.
• Revenue is not publicly disclosed on a drug-specific basis and is likely small relative to major antidepressant products.
• Demand is structurally limited by competition from SSRIs, SNRIs, atypical antidepressants, and other modern therapies.
• Supply concentration and manufacturer exits create greater commercial risk than patent infringement.
• A new generic entrant could obtain broad legal freedom to operate but would face a small, price-sensitive market.
• The most credible financial outlook is a mature, low-revenue market with episodic supply-driven pricing volatility rather than sustained growth.

FAQs

Is amoxapine still available in the United States?

Yes. Amoxapine remains an FDA-approved generic prescription tablet, although availability can vary by strength, manufacturer, and pharmacy inventory.

Is amoxapine a controlled substance?

No. Amoxapine is not classified as a U.S. controlled substance. It is dispensed by prescription because of its psychiatric indications and safety profile.

Can a generic company launch amoxapine without a patent license?

Generally, yes, provided the applicant satisfies FDA requirements and addresses any current Orange Book listing or regulatory exclusivity. No commercially significant patent license is generally required for the conventional tablet.

Does amoxapine have a 180-day generic exclusivity period?

A 180-day exclusivity period could apply to a qualifying first ANDA applicant under the Hatch-Waxman framework, but amoxapine is a long-established generic product and does not present a current first-filer exclusivity opportunity of material commercial importance.

Is amoxapine a potential reformulation opportunity?

Technically, a reformulation could be developed, but the commercial case is weak. A new dosage form would need to produce a clinically meaningful benefit sufficient to offset development, regulatory, manufacturing, and market-access costs in a small patient population.

References

DailyMed. (n.d.). Amoxapine tablet prescribing information. U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/

U.S. Food and Drug Administration. (n.d.-a). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/

U.S. Food and Drug Administration. (n.d.-b). Drugs@FDA: FDA-approved drugs. https://www.accessdata.fda.gov/scripts/cder/daf/

U.S. National Library of Medicine. (n.d.). Amoxapine. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/Amoxapine

U.S. Food and Drug Administration. (2016). Drug products approved under the abbreviated new drug application pathway. https://www.fda.gov/drugs/abbreviated-new-drug-application-anda/anda-process