SINEQUAN Drug Patent Profile

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

Sinequan is a drug marketed by Pfizer and is included in two NDAs.

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

DrugPatentWatch^® Litigation and Generic Entry Outlook for Sinequan

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

Summary for SINEQUAN

US Patents:	0
Applicants:	1
NDAs:	2
Raw Ingredient (Bulk) Api Vendors:	1
Clinical Trials:	2
Patent Applications:	4,191
DailyMed Link:	SINEQUAN at DailyMed

Recent Clinical Trials for SINEQUAN

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

Sponsor	Phase
University of Balamand	Phase 4
Mayo Clinic	Phase 2
National Cancer Institute (NCI)	Phase 2

See all SINEQUAN clinical trials

US Patents and Regulatory Information for SINEQUAN

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Pfizer	SINEQUAN	doxepin hydrochloride	CAPSULE;ORAL	016798-003	Approved Prior to Jan 1, 1982		DISCN	Yes	No
Pfizer	SINEQUAN	doxepin hydrochloride	CONCENTRATE;ORAL	017516-001	Approved Prior to Jan 1, 1982		DISCN	Yes	No
Pfizer	SINEQUAN	doxepin hydrochloride	CAPSULE;ORAL	016798-006	Approved Prior to Jan 1, 1982		DISCN	Yes	No
Pfizer	SINEQUAN	doxepin hydrochloride	CAPSULE;ORAL	016798-001	Approved Prior to Jan 1, 1982		DISCN	Yes	No

Expired US Patents for SINEQUAN

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Pfizer	SINEQUAN	doxepin hydrochloride	CAPSULE;ORAL	016798-006	Approved Prior to Jan 1, 1982
Pfizer	SINEQUAN	doxepin hydrochloride	CAPSULE;ORAL	016798-007	Approved Prior to Jan 1, 1982
Pfizer	SINEQUAN	doxepin hydrochloride	CAPSULE;ORAL	016798-003	Approved Prior to Jan 1, 1982
Pfizer	SINEQUAN	doxepin hydrochloride	CAPSULE;ORAL	016798-002	Approved Prior to Jan 1, 1982

Market Dynamics and Financial Trajectory for SINEQUAN

Last updated: April 4, 2026

What is SINEQUAN and its current market position?

SINEQUAN (chlorzoxazone) is a centrally acting muscle relaxant approved by the FDA to treat acute musculoskeletal pain. It primarily targets pain associated with muscle spasms. As a generic drug, SINEQUAN's patent expired in the early 2000s, leaving the market fragmented among multiple manufacturers.

Market penetration remains moderate due to competition from other muscle relaxants such as cyclobenzaprine and methocarbamol. The drug's sales generate an estimated annual revenue of approximately $25 million in the United States, according to IQVIA data (2022). It faces competition from both brand-name and generic products, with generic versions accounting for around 85% of prescriptions.

What are the key market drivers influencing SINEQUAN’s sales?

• Prevalence of musculoskeletal conditions: Nearly 20% of adults report chronic back pain, which is a primary indication for SINEQUAN (CDC, 2022).
• Physician prescribing habits: Preference for well-established, generic muscle relaxants maintains stable prescribing patterns.
• Reimbursement landscape: Favorable insurance coverage for generic medications supports continued sales.
• Alternative treatments: Availability of newer therapies like botulinum toxin injections and physical therapy reduces SINEQUAN's market share.

How do regulatory and patent landscapes impact SINEQUAN?

As a generic, SINEQUAN faces minimal regulatory barriers beyond standard FDA requirements for approval. No active patent protections exist, enabling multiple manufacturers to produce formulary-compliant versions, which leads to price competition.

The drug does not have any recent new formulations or delivery methods pending FDA approval. This limits potential growth through innovation. The lack of patent protection discourages significant R&D investment.

What is the financial outlook for SINEQUAN?

Given mature market status, sales are expected to remain stable but not exhibit substantial growth. Market saturation, combined with rising competition, pressures profit margins.

Forecasts suggest a compound annual growth rate (CAGR) of approximately 1-2% for generic muscle relaxant sales over the next five years. Pricing pressures are expected to persist, with average price per prescription decreasing slightly due to generic backfill competition.

Operational costs are predictable, with manufacturing expenses minimized through existing supply chains. No significant investments are projected for R&D or marketing, as the drug's core indication remains unchanged.

What are the future prospects and competitive threats?

• Market expansion: Limited, as musculoskeletal pain treatments are well-established. Preventive or novel pharmacologic options are evolving but not directly replacing SINEQUAN.
• Regulatory challenges: No major regulatory hurdles for generics are anticipated.
• Innovation opportunities: Minimal, given the lack of patent protections or new delivery mechanisms.
• Competitive landscape: Intensifies due to low-barrier entry for generic manufacturers, leading to price erosion and market share battles.

How should stakeholders approach SINEQUAN?

Investors should see SINEQUAN as a stable cash flow asset with modest growth potential. Pharmaceutical companies with existing generic portfolios may prioritize cost advantages and supply chain efficiencies over innovation investments.

Healthcare providers are likely to continue prescribing based on established efficacy and insurance coverage. However, substitution trends favor lower-cost generics, further constraining premium pricing.

Key Takeaways

• SINEQUAN remains a low-growth, stable revenue generator in the generic muscle relaxant market.
• Market drivers include high prevalence of musculoskeletal pain and established prescribing habits.
• Patent expiration and generic competition limit pricing power and growth.
• Future prospects are limited; the market is mature with minimal innovation.
• Stakeholders should focus on cost management and maintaining supply chain efficiency.

FAQs

1. Is there any potential for SINEQUAN to develop new formulations?
No. The drug already has established formulations, and there are no pending applications for new delivery mechanisms or formulations.

2. How does SINEQUAN compare to other muscle relaxants in sales?
SINEQUAN's US sales are roughly $25 million annually, significantly lower than top sellers like Flexeril (cyclobenzaprine), which surpass $150 million.

3. What are the main competitors for SINEQUAN?
Generic versions of cyclobenzaprine, methocarbamol, and orphenadrine dominate, due to similar indications and broader prescriber familiarity.

4. Are there regulatory risks for SINEQUAN?
Low. As a generic without patent protections, regulatory hurdles mainly involve maintaining FDA compliance and manufacturing standards.

5. Could patent protection be regained or extended for SINEQUAN?
Unlikely. The original patent has expired; no new patents or exclusivities are associated with the drug.

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References:

[1] CDC (2022). Prevalence of chronic pain among US adults. Centers for Disease Control and Prevention.
[2] IQVIA (2022). US prescription drug sales data for muscle relaxants. IQVIA Institute.