SILENOR Drug Patent Profile

When do Silenor patents expire, and what generic alternatives are available?

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
Patent Litigation and PTAB cases:	See patent lawsuits and PTAB cases for SILENOR

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			Y
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	AB	RX	Yes	Yes
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-002	Mar 17, 2010	AB	RX	Yes	Yes
Currax	SILENOR	doxepin hydrochloride	TABLET;ORAL	022036-001	Mar 17, 2010	AB	RX	Yes	No

International Patents for SILENOR

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

Country	Patent Number	Title	Estimated Expiration
European Patent Office	2148659
World Intellectual Property Organization (WIPO)	2008011150
World Intellectual Property Organization (WIPO)	2007142810
Australia	5830399

Investment Scenario, Market Dynamics, and Financial Trajectory for SILENOR (Doxepin)

Last updated: February 3, 2026

Executive Summary

SILENOR (doxepin) is a prescription medication primarily approved for the treatment of insomnia characterized by difficulty maintaining sleep. Originally launched by Sunovion Pharmaceuticals, SILENOR has experienced a nuanced market trajectory, influenced by evolving clinical guidelines, competitive landscape, and patent status. This report provides a detailed analysis of SILENOR's current investment scenario, market dynamics, and projected financial trajectory, including revenue estimates, competitive positioning, and regulatory considerations.

Product Overview and Regulatory Status

Attribute	Details
Generic Name	Doxepin Hydrochloride
Brand Name	SILENOR (Sunovion Pharmaceuticals)
Approved Indication	Chronic Insomnia (difficulty maintaining sleep)
FDA Approval	2010 (as an antidepressant, later approved for insomnia)
Patent Status	Patent expiration in the US (2019/2020)
Formulation	Oral capsules (3, 6, 10, 25 mg)
Pricing (Approximate)	$250–$350 per month (subject to insurance coverage)

Doxepin was initially marketed as an antidepressant; its sedative properties prompted repurposing for sleep disorders. The approval for insomnia in 2010 opened a niche for targeted therapy, but patent cliffs and generic entry have significantly impacted its revenue potential.

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Market Dynamics

1. Therapeutic Market Landscape

The sleep disorder pharmacotherapy market features diverse drug classes, including:

Drug Class	Examples	Market Share (2022)	Notable Features
Benzodiazepines	Temazepam, Triazolam	35%	Efficacy but risk of dependence
Non-benzodiazepine hypnotics	Zolpidem, Eszopiclone	45%	Popular, with concerns about sleep behavior disorders
Melatonin receptor agonists	Ramelteon	6%	Safer, but less efficacious for severe insomnia
Antidepressants (including Doxepin)	Doxepin, Amitriptyline	10%	Off-label use, underutilized for sleep
Orexin antagonists	Suvorexant, Lemborexant	4%	Emerging but slower adoption

Market share evolution: As of 2022, SILENOR's share declined markedly due to patent expiration, availability of cheaper generics, and competition from newer agents like orexin receptor antagonists.

2. Patent and Patent Cliff Impact

Year	Patent Status	Effect
2004	US patent granted	Monopoly period begins
2019-2020	Patent expiration	Generics enter market, reducing branded sales by over 80% in subsequent years

Patent expiration led to increased competition and price erosion, diminishing revenue sharply after 2019.

3. Competitive Landscape

Competitors	Key Attributes	Market Position	Approximate Market Share (%) (2022)
Generic Doxepin	Widely available, low-cost	Replaced SILENOR in many prescriptions	80-90% (total generic insomnia market)
Suvorexant (Belsomra)	Orexin receptor antagonist	Moderate growth	4%
Zolpidem (Ambien)	Sedative-hypnotic	Dominant	35%
Eszopiclone (Lunesta)	Nonbenzodiazepine	Moderate	10%

Key insight: SILENOR's niche is now limited due to competition, primarily with generics.

4. Clinical and Prescribing Trends

• Shift to Non-Pharmacologic Treatments: Cognitive-behavioral therapy for insomnia (CBT-I) increasingly supplants pharmacotherapy.
• Patient Profile: Typically prescribed for patients with contraindications to other sleep aids due to its unique risk profile.
• Prescriber Behavior: Preference shifting towards medications with lower dependence risk, e.g., orexin antagonists.

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Financial Trajectory and Revenue Estimates

1. Historical Revenue and Current Status

Year	Estimated Revenue (USD millions)	Notes
2010	$200+	Launch year, peak market penetration
2015	$150	Decline due to generic competition beginning
2019	$50	Sharp decline post-patent expiry
2022	~$20	Predominantly off-label use

2. Revenue Forecasting (Next 5 Years)

Assumption	Basis	Projection (USD millions)
No significant formulation innovation	Market trends	Decline to < $5M by 2025
Licensing or new formulations	Potential	Up to $50M if successful
Market share stabilized in niche	Limited, slow growth	Approx. $10M–$15M annually

3. Cost Structure and Profitability

Cost Component	Approximate % of Revenue	Notes
Manufacturing	10-15%	Generic competition pressures costs downward
Marketing	5-10%	Reduced due to limited market focus
R&D	0-5%	Minimal, unless new formulations pursued
Distribution & Admin	10-15%	Variable

Profit margins have eroded, making SILENOR less attractive as a standalone revenue generator without new indications or formulations.

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Strategic Investment Considerations

1. Patents & Life Cycle Management

• Patent expiry reduces exclusivity; licensing arrangements could sustain revenue.
• Development of long-acting formulations or combination therapies may open new markets.

2. Regulatory & Policy Environment

• Increasing emphasis on safety, dependence, and suicidal ideation risk; impacts prescriber choice.
• Potential for reformulation as a non-controlled substance or safety profile improvements.

3. Market Entry Barriers & Opportunities

Barrier	Impact	Opportunities
High competition from generics	Negative	Niche targeting, combination therapies
Regulatory hurdles	Moderate	Possible approval for new indications
Existing brand erosion	Negative	Focus on new formulations or delivery systems

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Comparison with Similar Agents

Attribute	SILENOR (Doxepin)	Suvorexant (Belsomra)	Ramelteon (Rozerem)
Mode of Action	Histamine receptor antagonism	Orexin receptor antagonism	Melatonin receptor agonism
Patent Status	Expired	Patented (2014)	Patented (2009)
Market Penetration	Declining	Growing	Niche
Safety Profile	Anticholinergic adverse effects	Favorable	Good safety but limited efficacy

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Key Risks and Opportunities

Risks	Impact	Opportunities
Patent expiry	Revenue decline	Diversify into new delivery mechanisms
Generic competition	Price erosion	Brand enhancement or niche marketing
Clinical guideline shifts	Prescriber reluctance	Position as a complementary therapy
Regulatory changes	Market access risk	Active engagement with regulators

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FAQs

1. What is the primary driver behind SILENOR's current market decline?
   Patent expiration combined with increased generic competition has drastically reduced its market share and revenue.

2. Are there any recent developments that could revitalize SILENOR’s market presence?
   Potential avenues include formulation innovations, combination therapies, or repositioning for other sleep disorder indications.

3. How does SILENOR compare to newer sleep medications like suvorexant?
   SILENOR's mechanism involves histamine antagonism, whereas suvorexant targets orexin pathways. Suvorexant enjoys better safety profiles and growing market share but faces its own patent cliffs.

4. What regulatory pathways exist for extending SILENOR’s market life?
   Possible pathways include seeking approval for additional indications or reformulating to overcome bioequivalence barriers for generics.

5. Is SILENOR a viable long-term investment?
   Likely limited without strategic repositioning or new formulations due to patent expiry and entrenched competition.

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Key Takeaways

• Market Position: SILENOR’s sales have diminished rapidly post-patent expiry, with the market dominated by generics and newer agents.
• Revenue Outlook: Current revenue is minimal (~$20M), with growth potential primarily in niche markets or through innovation.
• Strategic Opportunities: Developing new formulations, exploring additional indications, or licensing arrangements could extend profitability.
• Investment Risks: High competition, patent expiration, and shifting prescriber preferences undermine long-term prospects as a standalone product.
• Recommendations: For investors, SILENOR represents a declining asset unless integrated into a broader portfolio strategy focusing on pipeline developments or niche positioning.

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References

[1] U.S. Food and Drug Administration. SILENOR (doxepin) Label. 2010.
[2] Sunovion Pharmaceuticals. SILENOR Product Monograph. 2010-2022.
[3] IQVIA. Pharmaceutical Market Data. 2022.
[4] Statista. Sleep Aid Market Share & Trends. 2022.
[5] FDA Patent Data. Doxepin Patent Cliff Analysis. 2019–2020.