PROPOXYPHENE HYDROCHLORIDE 65 Drug Patent Profile

When do Propoxyphene Hydrochloride 65 patents expire, and when can generic versions of Propoxyphene Hydrochloride 65 launch?

Propoxyphene Hydrochloride 65 is a drug marketed by Warner Chilcott and is included in one NDA.

The generic ingredient in PROPOXYPHENE HYDROCHLORIDE 65 is propoxyphene hydrochloride. There is one drug master file entry for this compound. Additional details are available on the propoxyphene hydrochloride profile page.

Summary for PROPOXYPHENE HYDROCHLORIDE 65

US Patents:	0
Applicants:	1
NDAs:	1
Raw Ingredient (Bulk) Api Vendors:	16
Clinical Trials:	8
Patent Applications:	2,701
DailyMed Link:	PROPOXYPHENE HYDROCHLORIDE 65 at DailyMed

Recent Clinical Trials for PROPOXYPHENE HYDROCHLORIDE 65

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

Sponsor	Phase
Mansoura University	Phase 1/Phase 2
Federal University of São Paulo	Phase 4
Fundação de Amparo à Pesquisa do Estado de São Paulo	Phase 4

See all PROPOXYPHENE HYDROCHLORIDE 65 clinical trials

US Patents and Regulatory Information for PROPOXYPHENE HYDROCHLORIDE 65

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Warner Chilcott	PROPOXYPHENE HYDROCHLORIDE 65	propoxyphene hydrochloride	CAPSULE;ORAL	083786-001	Approved Prior to Jan 1, 1982		DISCN	No	No

Propoxyphene Hydrochloride 65 mg Market Dynamics, Financial Trajectory, and Regulatory Status

Last updated: September 25, 2026

Propoxyphene hydrochloride 65 mg, historically marketed in the United States as Darvon, is no longer a viable commercial pharmaceutical product in the U.S. The FDA requested withdrawal of all propoxyphene-containing products in November 2010 after studies showed dose-dependent cardiac conduction abnormalities, including QT-interval prolongation and risk of potentially fatal arrhythmias.[1] The product had already lost meaningful patent protection, faced extensive generic substitution, and was competing against newer analgesics. Its commercial trajectory ended through regulatory withdrawal rather than patent expiry alone.

What is propoxyphene hydrochloride 65 mg?

Propoxyphene hydrochloride 65 mg was an immediate-release opioid analgesic capsule used for mild to moderate pain. The product was chemically distinct from propoxyphene napsylate, the active ingredient used in Darvocet products containing acetaminophen.

Product	Active ingredient	Historical U.S. strength	Main manufacturer or sponsor	Status
Darvon	Propoxyphene hydrochloride	65 mg	Eli Lilly; later rights associated with Xanodyne	Withdrawn
Generic propoxyphene hydrochloride	Propoxyphene hydrochloride	65 mg	Multiple generic manufacturers	Withdrawn in the U.S.
Darvocet-N	Propoxyphene napsylate plus acetaminophen	50/325 mg and 100/650 mg	Eli Lilly; later Xanodyne	Withdrawn
Generic propoxyphene-acetaminophen	Propoxyphene napsylate plus acetaminophen	Various strengths	Multiple generic manufacturers	Withdrawn in the U.S.

Propoxyphene was a weak opioid with analgesic activity below that of morphine and commonly used for pain that was considered insufficiently severe to require stronger opioids. Its safety margin was narrow because toxicity could occur through respiratory depression, overdose, and cardiac electrophysiologic effects.

When did propoxyphene hydrochloride lose exclusivity?

Propoxyphene hydrochloride lost meaningful U.S. market exclusivity decades before its withdrawal. The product was introduced in the 1950s, and generic competition existed well before the final regulatory action in 2010.

Patent and exclusivity timeline

Event	Approximate timing	Commercial effect
Propoxyphene introduced in the U.S.	1950s	Originator launch
Darvon 65 mg commercialized	1950s	Initial branded opioid market
Generic propoxyphene products enter	Before 2010	Price and share erosion
Product-specific U.S. patent protection	Expired decades earlier	No modern patent barrier
FDA safety restrictions and labeling changes	2009	Demand reduction
FDA withdrawal request	November 2010	U.S. market termination
Final U.S. commercial availability	Late 2010 to early 2011	Revenue effectively ended

No active patent estate is known to provide current exclusivity for propoxyphene hydrochloride 65 mg in the United States. Any historical composition-of-matter or product patents are long expired. Formulation, manufacturing, or method-of-use patents would not restore commercial value after withdrawal of the active ingredient from the U.S. market.

What is the FDA and Orange Book status of propoxyphene 65 mg?

The FDA requested withdrawal of all propoxyphene products from the U.S. market on November 19, 2010. The agency cited new evidence that therapeutic doses could produce significant changes in cardiac electrical activity.[1]

The regulatory sequence was:

1. The FDA required stronger warnings in 2009 after reviewing overdose and cardiac safety concerns.
2. The agency required a new boxed warning and medication guide.
3. FDA analysis found dose-dependent QT prolongation at therapeutic doses.
4. The agency concluded that the safety risks outweighed the modest analgesic benefit.
5. Manufacturers agreed to withdraw propoxyphene products.

The historical Orange Book status is therefore more relevant than a current listing. Darvon and generic propoxyphene products are not viable active U.S. Orange Book products. The product’s regulatory withdrawal eliminated the practical value of any abbreviated new drug application pathway.

Did propoxyphene face Paragraph IV challenges?

Paragraph IV litigation was not the main commercial issue for propoxyphene hydrochloride 65 mg. The product’s relevant patent rights had expired long before the 2010 withdrawal, and generic versions had already entered the market. The principal legal and commercial risk was product liability and regulatory action, not patent litigation.

Why was propoxyphene withdrawn?

The FDA’s decision rested on cardiac safety rather than a failure of analgesic efficacy. In a randomized crossover study, propoxyphene produced statistically significant QT-interval prolongation at therapeutic doses. Higher exposure, including exposure associated with overdose or impaired metabolism, increased the risk of serious arrhythmia.[1]

The risk profile was aggravated by:

• Narrow therapeutic separation between analgesic and toxic exposure.
• Use in older patients with cardiovascular disease.
• Accumulation in renal or hepatic impairment.
• Frequent combination use with alcohol, sedatives, or other opioids.
• Availability of safer analgesic alternatives.

The European Medicines Agency recommended suspension of dextropropoxyphene products in 2009 after concluding that the benefits did not outweigh the risks.[2] The United Kingdom had already restricted or withdrawn the medicine earlier because of overdose and suicide concerns.

How did the market for propoxyphene change before withdrawal?

The product moved through three commercial phases.

1. Branded growth and broad primary-care use

Darvon became a widely prescribed oral analgesic. Its 65 mg capsule was simple to manufacture and distribute, and physicians used it for mild to moderate pain. The product benefited from the historical expansion of outpatient prescription analgesics.

2. Generic erosion and therapeutic substitution

Generic propoxyphene reduced pricing power. The product also faced competition from:

• Acetaminophen and nonsteroidal anti-inflammatory drugs.
• Codeine combinations.
• Hydrocodone-acetaminophen products.
• Tramadol.
• Oxycodone combinations.
• Nonpharmacologic pain-management approaches.

The strongest commercial substitutes were combination analgesics and other low- to moderate-potency opioids. Propoxyphene’s relatively weak efficacy limited its ability to command a premium after generic entry.

3. Regulatory contraction and market exit

Warnings, physician concerns, and decreasing use reduced demand before the final withdrawal. After the FDA action, legal U.S. sales ended. The market did not transition to a higher-priced replacement formulation because the active ingredient itself was removed from the market.

What was the financial trajectory of propoxyphene hydrochloride 65 mg?

The financial trajectory was a long decline from a large legacy product to zero U.S. revenue.

Period	Financial condition	Main driver
1950s-1980s	High-volume branded product	Broad prescribing and limited competition
1990s-2000s	Mature, declining product	Generic entry and substitution
2009	Accelerated erosion	Safety warnings and declining physician confidence
2010	Imminent commercial termination	FDA withdrawal request
2011 onward	No U.S. product revenue	Market withdrawal

Public filings generally reported company-wide revenue or broader product portfolios rather than audited revenue for propoxyphene hydrochloride 65 mg alone. Product-level revenue should therefore not be treated as a verified figure unless supported by prescription-audit data or a company filing that separately identifies Darvon sales.

FDA safety communications reported that approximately 10 million U.S. patients were prescribed propoxyphene products in 2009, indicating substantial historical volume.[1] That patient exposure does not translate directly into manufacturer revenue because the market included low-priced generics and combination products.

The commercial value of the product in 2010 was constrained by four factors:

1. No meaningful patent exclusivity.
2. Extensive generic competition.
3. Weak differentiation from alternative analgesics.
4. Imminent regulatory removal.

What patent estate protected propoxyphene hydrochloride 65 mg?

The relevant patent estate was historical, not current.

Active ingredient patents

Propoxyphene was discovered and commercialized in the mid-20th century. Any original compound patents expired many years ago. No current U.S. composition-of-matter patent can block generic entry or support an exclusivity premium for the 65 mg hydrochloride capsule.

Formulation patents

The 65 mg product was a conventional immediate-release oral capsule. Such a formulation generally offers limited patentability compared with extended-release systems, transdermal systems, injectables, or complex delivery platforms. Historical formulation patents, if any, are expired or commercially irrelevant following withdrawal.

Method-of-use patents

Potential method-of-use claims for treating pain would have faced broad prior-art challenges and could not overcome the FDA’s conclusion that the overall benefit-risk balance was unfavorable. There is no current U.S. method-of-use exclusivity supporting commercial distribution of propoxyphene hydrochloride 65 mg.

What patent litigation and settlements affected the product?

No current patent litigation materially affects propoxyphene hydrochloride 65 mg. The product’s commercial termination was driven by regulatory withdrawal and safety litigation exposure rather than a contemporary patent dispute.

The relevant legal risks included:

• Product-liability claims involving overdose.
• Claims involving cardiac toxicity.
• Failure-to-warn allegations.
• Litigation concerning continued marketing after safety signals.
• Regulatory enforcement and withdrawal consequences.

Settlement agreements involving historical propoxyphene litigation do not create market exclusivity or provide a basis for generic launch. They primarily affect liability allocation and legal cost.

Which companies challenged or competed with propoxyphene?

The product faced competition from both generic manufacturers and alternative analgesic suppliers.

Competitive group	Examples	Competitive effect
Generic propoxyphene manufacturers	Multiple ANDA holders	Reduced price and brand share
Acetaminophen products	OTC and prescription products	Substituted in lower-acuity pain
NSAIDs	Ibuprofen, naproxen, diclofenac	Competed in inflammatory pain
Tramadol suppliers	Brand and generic manufacturers	Offered an alternative weak opioid
Hydrocodone suppliers	Multiple generic and branded firms	Captured moderate-pain prescriptions
Oxycodone suppliers	Brand and generic manufacturers	Captured stronger analgesic demand

The market was fragmented, but hydrocodone combinations represented a particularly important substitute in U.S. prescribing. Tramadol also competed for patients who required an opioid-like analgesic but not a high-potency opioid.

What generic entry risks existed for propoxyphene 65 mg?

Before withdrawal, generic entry risk was high and conventional:

• The active ingredient was off patent.
• The dosage form was technically simple.
• Bioequivalence could be demonstrated through standard pharmacokinetic testing.
• Manufacturing did not require specialized biologic or device technology.
• Multiple suppliers could compete on price.

After withdrawal, the risk profile changed. A generic manufacturer could not commercially relaunch the product in the U.S. merely by relying on historical approval. It would face FDA regulatory barriers, safety concerns, labeling requirements, and potential refusal based on the agency’s benefit-risk position.

How strong was the manufacturing and intellectual-property barrier?

The manufacturing barrier was low. Propoxyphene hydrochloride 65 mg was a conventional small-molecule oral capsule. Manufacturing required standard active pharmaceutical ingredient production, blending, encapsulation, quality testing, and packaging.

The principal barriers were regulatory and liability-related:

Barrier	Assessment
Chemical synthesis	Low to moderate
Oral capsule manufacturing	Low
Bioequivalence	Low to moderate
Patent protection	Negligible
Regulatory re-entry	Very high
Product-liability exposure	Very high
Commercial differentiation	Low

This profile explains why the product was economically vulnerable before withdrawal. Its manufacturing simplicity did not create a durable competitive advantage.

Is there biosimilar risk for propoxyphene hydrochloride 65 mg?

No. Propoxyphene hydrochloride is a chemically synthesized small molecule, not a biologic. Biosimilar regulation under the Public Health Service Act does not apply. Any follow-on product would be evaluated through the generic drug framework, principally an ANDA or, depending on the regulatory circumstances, another FDA application pathway.

What generic launch scenarios remain?

A conventional U.S. generic launch is commercially improbable because the FDA withdrew propoxyphene products over safety concerns. Three scenarios can be distinguished:

Scenario	Probability assessment	Commercial implication
Routine U.S. generic launch	Remote	No viable market under current regulatory position
Reformulated product with improved safety	Highly unlikely	Would require substantial clinical and regulatory support
Non-U.S. sale in a jurisdiction permitting use	Jurisdiction-dependent	Limited and declining opportunity
Competing alternative analgesics	Ongoing	Main source of replacement demand

A reformulation would not solve the core issue unless it materially reduced systemic exposure or cardiac risk. Developing such a product would require clinical evidence disproportionate to the remaining market opportunity.

How does propoxyphene compare with competing analgesics?

Attribute	Propoxyphene HCl 65 mg	Tramadol	Hydrocodone combinations	NSAIDs
U.S. status	Withdrawn	Marketed	Marketed under controlled-substance rules	Marketed
Patent barrier	Expired	Mostly expired	Mostly expired	Mostly expired
Analgesic potency	Low	Low to moderate	Moderate to high	Non-opioid
Cardiac safety concern	Major withdrawal driver	Different risk profile	Respiratory-depression risk	Gastrointestinal and renal risks
Generic competition	Historical	Extensive	Extensive	Extensive
Current commercial relevance	None in U.S.	Material	Material	Material

Propoxyphene’s principal disadvantage was not only weak analgesic performance. It was the combination of limited efficacy, generic pricing, and an unfavorable safety profile that alternatives could better address.

Key Takeaways

• Propoxyphene hydrochloride 65 mg was the active ingredient in Darvon, a legacy oral opioid analgesic.
• U.S. patent exclusivity expired decades before the product’s withdrawal.
• The FDA requested withdrawal in November 2010 because of QT prolongation and potentially fatal cardiac arrhythmias.
• There is no current U.S. commercial market, meaningful Orange Book opportunity, or biosimilar pathway.
• Generic competition had already compressed pricing and brand value before regulatory withdrawal.
• The product’s financial trajectory ended at effectively zero U.S. revenue after withdrawal.
• Regulatory and liability barriers, rather than manufacturing complexity or patent strength, prevent a credible U.S. relaunch.
• Tramadol, hydrocodone combinations, NSAIDs, acetaminophen, and other analgesics captured replacement demand.

FAQs

Is propoxyphene hydrochloride 65 mg still available in the United States?

No. The FDA requested withdrawal of all propoxyphene-containing products in 2010, and the product is not a current U.S. commercial analgesic.

Was Darvon the same as Darvocet?

No. Darvon contained propoxyphene hydrochloride alone. Darvocet contained propoxyphene napsylate combined with acetaminophen.

Can a company launch a generic propoxyphene 65 mg capsule today?

A routine ANDA-based launch would not provide a practical route to U.S. commercialization because the active ingredient was withdrawn for safety reasons. A new sponsor would face substantial FDA and clinical barriers.

Did propoxyphene have a biosimilar competitor?

No. Propoxyphene is a small-molecule drug. The relevant follow-on framework is generic-drug regulation, not biosimilar regulation.

What replaced propoxyphene in the pain market?

Prescribing shifted toward acetaminophen, NSAIDs, tramadol, hydrocodone combinations, oxycodone products, and nonpharmacologic pain-management approaches, depending on pain severity and patient risk.

References

1. U.S. Food and Drug Administration. (2010, November 19). FDA recommends withdrawal of propoxyphene products from the U.S. market. https://www.fda.gov
2. European Medicines Agency. (2009, June 25). European Medicines Agency recommends withdrawal of dextropropoxyphene-containing medicines. https://www.ema.europa.eu
3. U.S. Food and Drug Administration. (2009, July 7). FDA strengthens warnings for propoxyphene-containing products. https://www.fda.gov
4. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov
5. U.S. Food and Drug Administration. (2010). Propoxyphene: Questions and answers. https://www.fda.gov