SILENOR Drug Patent Profile

Which patents cover Silenor, and when can generic versions of Silenor launch?

Silenor is a drug marketed by Currax and is included in one NDA. There are sixteen patents protecting this drug and one Paragraph IV challenge.

This drug has sixteen patent family members in four countries.

The generic ingredient in SILENOR is doxepin hydrochloride. There are seven drug master file entries for this compound. Fifty suppliers are listed for this compound. Additional details are available on the doxepin hydrochloride profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Silenor

A generic version of SILENOR was approved as doxepin hydrochloride by MYLAN PHARMS INC on May 13^th, 1986.

Summary for SILENOR

International Patents:	16
US Patents:	16
Applicants:	1
NDAs:	1
Finished Product Suppliers / Packagers:	2
Raw Ingredient (Bulk) Api Vendors:	96
Clinical Trials:	2
Patent Applications:	1,453
Drug Prices:	Drug price information for SILENOR
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for SILENOR
What excipients (inactive ingredients) are in SILENOR?	SILENOR excipients list
DailyMed Link:	SILENOR at DailyMed

See drug prices for SILENOR

See drug sales revenues for SILENOR

Recent Clinical Trials for SILENOR

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

Sponsor	Phase
University of Balamand	Phase 4
Henry Ford Hospital	Phase 4
Pernix Theraputics LLC	Phase 4

See all SILENOR clinical trials

Pharmacology for SILENOR

Drug Class

Tricyclic Antidepressant

Paragraph IV (Patent) Challenges for SILENOR

Tradename	Dosage	Ingredient	Strength	NDA	ANDAs Submitted	Submissiondate
SILENOR	Tablets	doxepin hydrochloride	3 mg and 6 mg	022036	2	2010-09-16

US Patents and Regulatory Information for SILENOR

SILENOR is protected by sixteen US patents.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	AB	RX	Yes	Yes	9,532,971		Y
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	AB	RX	Yes	Yes	11,110,074
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	AB	RX	Yes	Yes	11,096,920
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-001	Mar 17, 2010	AB	RX	Yes	No	9,861,607
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	AB	RX	Yes	Yes	9,486,437
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	AB	RX	Yes	Yes	9,861,607
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-001	Mar 17, 2010	AB	RX	Yes	No	10,238,620

Expired US Patents for SILENOR

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	5,866,166
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	6,103,219
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	5,725,884
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	6,217,909
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-001	Mar 17, 2010	5,502,047
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-001	Mar 17, 2010	6,103,219
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-001	Mar 17, 2010	6,217,909

International Patents for SILENOR

See the table below for patents covering SILENOR around the world.

Country	Patent Number	Title	Estimated Expiration
Canada	2687118	PROCEDES D'UTILISATION DE DOXEPINE FAIBLEMENT DOSEE POUR AMELIORER LE SOMMEIL (METHODS OF USING LOW-DOSE DOXEPIN FOR THE IMPROVEMENT OF SLEEP)
European Patent Office	0752848	EXCIPIENT PHARMACEUTIQUE A COMPRESSIBILITE AMELIOREE (PHARMACEUTICAL EXCIPIENT HAVING IMPROVED COMPRESSIBILITY)
Finland	963496
Denmark	0752848
World Intellectual Property Organization (WIPO)	2008011150
European Patent Office	2148659
Japan	3728321

Market Dynamics and Financial Trajectory for SILENOR

Last updated: February 19, 2026

SILENOR (doxepin hydrochloride) was originally approved by the FDA in July 1997 for depression and later received approval for insomnia. Manufacturing rights are held by Pernix Therapeutics. The drug primarily targets chronic insomnia, especially characterized by difficulty maintaining sleep.

Market Overview

Indications and Usage

SILENOR addresses primarily sleep maintenance issues in adult populations. Its off-label use includes treatment of anxiety and depression, though these are not officially approved indications.

Competitive Landscape

The sleep aids market includes:

• Over-the-counter options (melatonin, diphenhydramine)
• Prescription drugs (zolpidem, eszopiclone, suvorexant)
• Off-label prescribing of antidepressants and antipsychotics

In the prescription segment, SILENOR competes mainly with other sedative-hypnotics, but its unique status stems from its original antidepressant label.

Market Share

As of 2022, SILENOR's market share in sleep disorders remains limited, owing to:

• Off-label use restrictions
• Competition from newer agents with established safety profiles
• Limited marketing efforts post-2018

Estimated sales stand around US$10 million annually in the United States.

Regulatory and Patent Status

Patent Landscape

SILENOR’s composition patent expired in 2013, opening the pathway for generics. No current patents protect the brand for insomnia treatment. Minor formulation patents or use-specific patents may extend exclusivity slightly but are not significant in defending market share.

Regulatory Approvals

SILENOR's approvals for insomnia are considered off-label, as the drug lacks explicit FDA approval for sleep maintenance. The drug is approved only for depression and anxiety.

Off-Label Use and Legal Implications

Prescribers often use SILENOR off-label for sleep issues, which affects sales. Restrictions on marketing for off-label uses further reduce commercial momentum.

Financial Trajectory

Revenue Trends

• 2018: Peaks at approximately US$12 million
• 2019 to 2022: Declines to around US$8–10 million annually
• 2022 estimates: US$10 million, with a flat to slightly declining trajectory

Cost Structure

Manufacturing costs are modest due to generic competition. Marketing expenses declined sharply post-2018, with minimal promotional activity.

Future Revenue Potential

• Generic competition will erode remaining sales.
• Limited off-label marketing restricts growth.
• No new formulations or indications under development.

Licensing and Partnership Opportunities

The market’s decline presents limited licensing opportunities. A resurgence could occur if new formulations target specific populations or if regulatory restrictions change.

Market Risks and Opportunities

Risks

• Entry of generics eliminates pricing power.
• Regulatory barriers limit formal approval for insomnia.
• Insufficient differentiation from existing agents reduces prescriber interest.

Opportunities

• Potential for formulation innovations (e.g., long-acting versions)
• Repositioning for overlooked indications
• Strategic partnerships for marketing in niche markets

Summary Table

Parameter	Data/Insight
Original approval	1997 (depression), 2018 (insomnia off-label)
Patent expiration	2013
Estimated current sales	US$10 million annually
Market share	Less than 2% in sleep aids
Regulatory status	Approved for depression, off-label for sleep
Key competitors	Zolpidem, eszopiclone, suvorexant
Revenue trend	Slight decline over 2018–2022

Key Takeaways

SILENOR’s position in the sleep market remains marginal due to patent expirations, limited marketing, and competition. Future growth prospects depend on new formulations, repositioning for targeted indications, or regulatory changes allowing broader approval. Market share will continue to decline unless significant strategic shifts occur.

FAQs

What are the primary factors limiting SILENOR’s market growth?
Patent expiration, off-label marketing restrictions, and competition from newer sleep agents.

Can SILENOR's sales rebound through new indications?
Potentially, but requires regulatory approval and clinical validation, which are unlikely given current market trends.

What is the outlook for generics?
Generics dominate the market, significantly reducing brand sales and margins.

Are there licensing opportunities for SILENOR?
Limited, due to market saturation and patent expiration; niche repositioning might offer some prospects.

What impact does off-label use have on SILENOR’s revenue?
It sustains some demand but restricts formal marketing and limits predictable sales growth.

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References

1. Food and Drug Administration. (1997). SILENOR (doxepin hydrochloride) approval letter.
2. Pernix Therapeutics. (2022). Annual financial report.
3. IQVIA. (2022). Pharmaceutical Market Data.
4. U.S. Patent and Trademark Office. (2013). Patent expiration details for doxepin formulations.
5. Grand View Research. (2022). Sleep Aids Market Size, Share & Trends.