ASPIRIN; PROPOXYPHENE HYDROCHLORIDE - Generic Drug Details

What are the generic drug sources for aspirin; propoxyphene hydrochloride and what is the scope of patent protection?

Aspirin; propoxyphene hydrochloride is the generic ingredient in one branded drug marketed by Xanodyne Pharm and is included in one NDA. Additional information is available in the individual branded drug profile pages.

Summary for ASPIRIN; PROPOXYPHENE HYDROCHLORIDE

US Patents:	0
Tradenames:	1
Applicants:	1
NDAs:	1
Clinical Trials:	1
DailyMed Link:	ASPIRIN; PROPOXYPHENE HYDROCHLORIDE at DailyMed

Recent Clinical Trials for ASPIRIN; PROPOXYPHENE HYDROCHLORIDE

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

See all ASPIRIN; PROPOXYPHENE HYDROCHLORIDE clinical trials

US Patents and Regulatory Information for ASPIRIN; PROPOXYPHENE HYDROCHLORIDE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Xanodyne Pharm	DARVON W/ ASA	aspirin; propoxyphene hydrochloride	CAPSULE;ORAL	010996-005	Approved Prior to Jan 1, 1982		DISCN	No	No

Aspirin and Propoxyphene Hydrochloride Market Dynamics, Financial Trajectory, and Patent Status

Last updated: September 8, 2026

Aspirin; propoxyphene hydrochloride is a discontinued opioid-analgesic combination associated with the former Darvon Compound product line. Its U.S. market ended after FDA required withdrawal of propoxyphene products in November 2010 because of cardiac conduction risks and overdose concerns. The product has no meaningful current U.S. revenue opportunity, no active biosimilar pathway, and little commercial value from its historical patent estate.

What was aspirin and propoxyphene hydrochloride?

Aspirin; propoxyphene hydrochloride combined an opioid analgesic with aspirin for the treatment of mild-to-moderate pain. Historical products in this category included propoxyphene hydrochloride formulations marketed under the Darvon name, including Darvon Compound products.

Propoxyphene was a centrally acting opioid introduced in the United States in the 1950s. The combination product competed with other low-potency opioid analgesics and later with acetaminophen-containing products such as Darvocet, which used propoxyphene napsylate rather than propoxyphene hydrochloride.

The product category had several commercial limitations:

• Propoxyphene provided relatively modest analgesic benefit.
• Aspirin created gastrointestinal bleeding and renal-risk concerns.
• Propoxyphene was associated with dose-related cardiac toxicity.
• Overdose could cause respiratory depression and fatal arrhythmias.
• Safer or more familiar alternatives became widely available.

FDA concluded that the risks of propoxyphene outweighed its benefits at recommended doses. The agency requested withdrawal of all propoxyphene-containing products from the U.S. market on November 19, 2010 (FDA, 2010).

What is the FDA regulatory status of aspirin and propoxyphene hydrochloride?

The product is discontinued in the United States. FDA’s 2010 withdrawal action covered both branded and generic propoxyphene products, including formulations containing propoxyphene hydrochloride and aspirin.

Regulatory event	Date	Commercial effect
FDA safety review identified cardiac conduction concerns	2009-2010	Risk-benefit profile deteriorated
European Medicines Agency recommended withdrawal of propoxyphene products	June 2009	International market contraction began
FDA requested voluntary withdrawal in the U.S.	November 19, 2010	U.S. sales terminated
Manufacturing and distribution ended	Late 2010 to early 2011	No ordinary U.S. commercial market remained

FDA cited evidence that propoxyphene could alter the electrical activity of the heart, including QT prolongation and widening of the QRS complex. The agency determined that the therapeutic benefit did not justify those risks, particularly because safer pain-treatment options were available (FDA, 2010).

The product does not have a current U.S. commercial approval supporting ordinary pharmacy distribution. Any historical listing in drug databases should be interpreted as discontinued status, not as evidence of an active market.

When did aspirin and propoxyphene hydrochloride lose exclusivity?

The product’s commercial exclusivity ended long before the 2010 safety withdrawal. Propoxyphene products had been sold for decades, and generic competition existed before market removal.

No current U.S. patent-based exclusivity appears to protect the historical aspirin-propoxyphene hydrochloride combination. The relevant commercial barriers were regulatory and safety-related rather than patent-related.

Exclusivity category	Current status
New chemical entity exclusivity	Expired decades ago
U.S. composition patent protection	Historical protection expired
Formulation patent protection	No material current protection identified
Method-of-use patent protection	No meaningful current protection identified
Orphan-drug exclusivity	Not applicable
Pediatric exclusivity	Not applicable
Biosimilar exclusivity	Not applicable
Current Orange Book patent strategy	No commercial value

The combination is a small-molecule drug product, not a biologic. Biosimilar substitution rules do not apply. Any hypothetical reintroduction would face FDA approval and safety-review requirements rather than a conventional patent-exclusivity hurdle.

What is the Orange Book status of aspirin and propoxyphene hydrochloride?

The product category has no active Orange Book commercial position comparable with currently marketed branded drugs. Historical products may appear in discontinued-product records or legacy drug databases, but discontinued status does not create an enforceable market right.

Orange Book implications are limited:

1. No current reference-product market supports an ordinary abbreviated new drug application strategy.
2. No active listed patent is known to create a practical barrier to competition.
3. A new applicant would need to address the underlying safety findings, not simply rely on expired historical approvals.
4. A future product would likely require a new regulatory strategy, new labeling, and updated benefit-risk evidence.

A company seeking to commercialize propoxyphene again would face substantially greater regulatory risk than patent risk. FDA’s withdrawal determination would be central to any development program.

How did the market for propoxyphene products perform before withdrawal?

Propoxyphene remained widely prescribed despite its limited analgesic efficacy. FDA reported that approximately 10 million U.S. patients received propoxyphene in 2009, with approximately 21 million prescriptions dispensed that year (FDA, 2010).

The market was supported by:

• Long physician familiarity.
• Low-cost generic supply.
• Established reimbursement pathways.
• A large installed base of chronic-pain patients.
• Historical use in patients seeking an alternative to stronger opioids.

The product was exposed to long-term erosion from generic competition and prescribing restrictions. Its market was also vulnerable to substitution by hydrocodone-acetaminophen, oxycodone-acetaminophen, tramadol, nonsteroidal anti-inflammatory drugs, and nonopioid analgesics.

Historical revenue trajectory

Public companies generally did not report revenue for aspirin-propoxyphene hydrochloride as a separate product. Available market data more commonly aggregated branded and generic propoxyphene products, including products containing acetaminophen rather than aspirin.

The financial trajectory can therefore be characterized directionally:

Period	Market condition	Revenue trajectory
1950s-1980s	Branded opioid analgesic with limited competition	Growth and maturity
1990s-2000s	Generic competition and substitution	Gradual erosion
2009	High prescription volume but increasing safety scrutiny	Mature, declining market
2010	FDA withdrawal decision	Abrupt collapse
2011 onward	No ordinary U.S. commercial sales	Effectively zero U.S. revenue

FDA’s action eliminated the principal U.S. revenue stream rather than merely reducing market share. For manufacturers, the withdrawal also created inventory write-offs, product-return obligations, discontinuation costs, and potential product-liability exposure.

What companies marketed or controlled propoxyphene products?

Eli Lilly originally commercialized Darvon in the United States. Xanodyne Pharmaceuticals later held U.S. rights to Darvon and Darvocet before agreeing to withdraw the products after FDA action. Generic manufacturers supplied equivalent propoxyphene products during the mature phase of the market.

The relevant commercial participants included:

Company type	Role
Eli Lilly	Original developer and historical marketer
Xanodyne Pharmaceuticals	Later U.S. rights holder for Darvon and Darvocet
Generic manufacturers	Supplied propoxyphene equivalents before withdrawal
Wholesalers and pharmacies	Distributed products until discontinuation

The product’s commercial value depended on legacy prescribing volume, not on a differentiated formulation or defensible patent position.

What patent litigation affected aspirin and propoxyphene hydrochloride?

No material current patent litigation is associated with the discontinued aspirin-propoxyphene hydrochloride market. Any historical patent disputes would have lost commercial relevance after the expiration of patent rights and the 2010 withdrawal.

The major legal exposure shifted from intellectual-property litigation to product-liability litigation. Propoxyphene manufacturers faced claims involving cardiac events, overdose, inadequate warnings, and alleged failure to withdraw the products sooner. Those claims did not create a pathway for generic entry because the entire product class was removed from the U.S. market.

No active Paragraph IV challenge has a meaningful commercial role today. Paragraph IV litigation is designed to challenge patents protecting an approved reference drug. Here, the relevant patents are historical, and the reference product is discontinued.

What formulation and method-of-use patents protected the product?

The historical product used a conventional oral dosage form. Its commercial protection did not depend on a technically complex delivery system.

Potential historical protection may have covered:

• Propoxyphene salt selection.
• Oral tablet or capsule formulations.
• Combination compositions containing aspirin.
• Manufacturing and compression methods.
• Pain-treatment methods.

Those protections are no longer commercially significant. There is no current evidence that a formulation patent protects a differentiated, marketable aspirin-propoxyphene hydrochloride product in the United States.

The combination also lacks the characteristics that support modern lifecycle management, such as extended-release delivery, abuse-deterrent technology, injectable delivery, transdermal administration, or a novel fixed-dose combination platform.

Are generic launch risks or licensing opportunities still relevant?

A conventional generic launch is not commercially attractive because the original product was withdrawn for safety reasons. FDA approval alone would not solve the market problem. A new applicant would need to address whether the product’s benefit-risk profile could support approval and broad prescribing.

The main risks would be:

• FDA refusal or heightened scrutiny based on the prior withdrawal.
• Product-liability exposure.
• Payer and pharmacy reluctance.
• Physician resistance.
• Opioid-related controlled-substance compliance obligations.
• Limited clinical differentiation.
• Availability of safer alternatives.

Licensing opportunities are similarly limited. Historical rights transfers involving Darvon products no longer represent a significant platform opportunity. The assets that retain potential value are more likely to be litigation-related, archival, or settlement-related than commercial.

How does aspirin-propoxyphene hydrochloride compare with competing pain drugs?

Product category	Market status	Competitive position
Aspirin plus propoxyphene hydrochloride	Withdrawn	No current U.S. market
Propoxyphene plus acetaminophen	Withdrawn	No current U.S. market
Hydrocodone-acetaminophen	Marketed under controlled-substance restrictions	Strong historical substitute
Oxycodone-acetaminophen	Marketed under controlled-substance restrictions	Higher-potency substitute
Tramadol	Marketed with opioid controls	Common lower-potency alternative
Aspirin or ibuprofen alone	Widely marketed	Nonopioid alternatives
Acetaminophen alone	Widely marketed	Lower-risk first-line alternative for some patients

Propoxyphene lost competitive relevance because its clinical benefit was limited while its safety profile was unfavorable. The withdrawal accelerated migration to other opioids and nonopioid analgesics.

What is the outlook for the product’s financial trajectory?

The U.S. financial trajectory is complete rather than recoverable. Revenue declined during the generic era and fell to approximately zero after withdrawal. There is no credible basis for projecting renewed U.S. sales without a new FDA-approved product and a materially different safety profile.

Commercial value is limited to:

• Historical market and prescribing data.
• Product-liability claims and defense positions.
• Regulatory and litigation records.
• Potential use as a case study in opioid risk management.
• Non-U.S. legacy information, where local regulatory status may differ.

A re-entry strategy would require a new clinical and regulatory justification. Patent protection would not provide the principal economic advantage.

Key Takeaways

• Aspirin; propoxyphene hydrochloride is a discontinued opioid-analgesic combination.
• FDA withdrew propoxyphene products from the U.S. market on November 19, 2010.
• FDA cited cardiac conduction abnormalities, overdose risk, and inadequate benefit relative to risk.
• The product had substantial prescription volume before withdrawal, with approximately 10 million U.S. patients exposed in 2009.
• Historical patent and exclusivity rights have expired or lost commercial relevance.
• No active biosimilar, Paragraph IV, or meaningful generic-entry opportunity exists.
• The U.S. revenue trajectory ended after withdrawal, and product-specific financial disclosures are not available as a separate public reporting category.
• Current value is primarily historical, regulatory, and litigation-related.

FAQs

Is aspirin and propoxyphene hydrochloride still available in the United States?

No. FDA-required withdrawal of propoxyphene products ended ordinary U.S. commercial availability in 2010 and early 2011.

Was propoxyphene hydrochloride more commercially important than propoxyphene napsylate?

Propoxyphene napsylate was used in major products such as Darvocet, while propoxyphene hydrochloride was used in Darvon and combination products. Public financial reporting generally aggregated the products, preventing a reliable molecule-salt revenue comparison.

Does aspirin-propoxyphene hydrochloride have remaining patent value?

No material current U.S. patent value is evident. The product’s patents and regulatory exclusivities are historical, and the commercial market ended because of safety concerns.

Could a company relaunch propoxyphene with a new formulation?

A relaunch would require FDA approval and a new benefit-risk justification. A novel formulation would not automatically overcome the cardiac safety findings associated with the active ingredient.

Did the FDA withdrawal apply only to branded products?

No. FDA’s action covered all propoxyphene-containing products, including branded and generic products and formulations using different propoxyphene salts.

References

1. U.S. Food and Drug Administration. (2010, November 19). FDA recommends against the continued use of propoxyphene. https://www.fda.gov/drugs/drug-safety-and-availability/fda-recommends-against-continued-use-propoxyphene

2. U.S. Food and Drug Administration. (2010, July 7). FDA drug safety communication: FDA recommends against the continued use of propoxyphene. https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/fda-drug-safety-communication-fda-recommends-against-continued-use-propoxyphene

3. European Medicines Agency. (2009, June 25). European Medicines Agency recommends withdrawal of dextropropoxyphene-containing medicines. https://www.ema.europa.eu

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