DARVON W/ ASA Drug Patent Profile

When do Darvon W/ Asa patents expire, and what generic alternatives are available?

Darvon W/ Asa is a drug marketed by Xanodyne Pharm and is included in one NDA.

The generic ingredient in DARVON W/ ASA is aspirin; propoxyphene hydrochloride. There is one drug master file entry for this compound. Additional details are available on the aspirin; propoxyphene hydrochloride profile page.

Summary for DARVON W/ ASA

US Patents:	0
Applicants:	1
NDAs:	1
DailyMed Link:	DARVON W/ ASA at DailyMed

US Patents and Regulatory Information for DARVON W/ ASA

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

DARVON W/ ASA Market Dynamics, Financial Trajectory, and Regulatory History

Last updated: August 22, 2026

DARVON W/ ASA was a legacy combination analgesic containing propoxyphene hydrochloride and aspirin. Its commercial value declined as safer pain treatments gained market share, generic competition increased, and regulators identified serious cardiac and overdose risks associated with propoxyphene. The U.S. market effectively ended in 2010 after the FDA requested withdrawal of all propoxyphene-containing products. No active U.S. commercial opportunity remains for the product.

What was DARVON W/ ASA?

DARVON W/ ASA was a prescription combination analgesic based on propoxyphene hydrochloride and aspirin. The product belonged to the same commercial family as Darvon, Darvon Compound-65, and other propoxyphene products.

The formulation historically associated with Darvon combination products contained approximately:

Component	Function
Propoxyphene hydrochloride	Opioid analgesic
Aspirin	Non-opioid analgesic and antipyretic
Caffeine in certain Darvon combination products	Analgesic adjuvant

Product formulations and labeling varied by country and by Darvon product. Darvon W/ ASA should not be confused with Darvocet-N, which combined propoxyphene napsylate with acetaminophen.

Propoxyphene was approved in the United States in the late 1950s. The product was initially positioned for mild-to-moderate pain, where its opioid component was intended to provide greater analgesia than aspirin alone.

How did the DARVON W/ ASA market develop?

DARVON W/ ASA entered a mature analgesic market dominated by aspirin, acetaminophen, nonsteroidal anti-inflammatory drugs, and stronger prescription opioids. Its commercial position depended on a perceived middle ground between non-opioid analgesics and higher-potency opioids.

That position weakened over time for four reasons:

1. Prescribers obtained broader access to alternative analgesics.
2. Generic propoxyphene products reduced pricing power.
3. Evidence accumulated regarding overdose toxicity and cardiac conduction abnormalities.
4. FDA and international regulators increased scrutiny of older opioid products.

Propoxyphene had a relatively narrow safety margin. Overdose could produce respiratory depression, coma, and death. The drug also was associated with QT prolongation and potentially fatal arrhythmias at therapeutic and supratherapeutic exposure levels. The presence of aspirin did not remove those risks.

The aspirin component introduced a separate risk profile, including gastrointestinal bleeding, ulceration, renal effects, and hypersensitivity. That combination created a weak long-term value proposition compared with products that offered more predictable efficacy or a more favorable safety profile.

When did DARVON W/ ASA lose market exclusivity?

DARVON W/ ASA lost meaningful market exclusivity decades before its U.S. withdrawal. Propoxyphene was an old small-molecule active ingredient, and generic propoxyphene products had entered the market well before the product’s final commercial decline.

The relevant commercial sequence was:

Period	Market event
Late 1950s	Propoxyphene approved and launched in the United States
1970s-1990s	Generic and competing propoxyphene products expand
1990s-2000s	Prescribing declines as alternative analgesics gain share
2009	European regulators recommend withdrawal of propoxyphene products
November 2010	FDA requests withdrawal of U.S. propoxyphene products
2010-2011	U.S. commercial distribution ends
After 2011	No meaningful U.S. market remains

No commercially relevant composition or formulation exclusivity protected DARVON W/ ASA at the time of withdrawal. Any historical patent rights covering propoxyphene or legacy dosage forms had expired or lost practical value.

What was the FDA regulatory status of DARVON W/ ASA?

The FDA’s final action was commercially decisive. On November 19, 2010, the agency requested that companies voluntarily withdraw all propoxyphene-containing products from the U.S. market after new data showed a risk of serious cardiac toxicity, including changes in cardiac electrical activity and potentially fatal arrhythmias [1].

The FDA concluded that the risks of propoxyphene outweighed its benefits for pain treatment. Xanodyne Pharmaceuticals agreed to withdraw Darvon and Darvocet products from the U.S. market. FDA communications directed patients and healthcare professionals to transition away from propoxyphene products [1].

The regulatory sequence followed action by the European Medicines Agency. In 2009, the EMA recommended withdrawal of propoxyphene-containing medicines from the European Union because the products provided limited pain relief and carried a risk of fatal overdose [2].

Was DARVON W/ ASA listed in the Orange Book?

Historical Darvon-related products were associated with approved U.S. drug applications, but withdrawn propoxyphene products no longer represented active commercial listings. The FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations, commonly called the Orange Book, identifies withdrawn approvals and regulatory status, but an historical listing does not create current market protection.

For a withdrawn product, the key commercial questions are whether:

• The reference drug remains approved.
• An ANDA remains eligible for approval.
• The reference product has active marketing status.
• The FDA has determined that withdrawal was related to safety or efficacy.

For propoxyphene, the withdrawal was safety-driven. That distinction makes a new generic launch commercially and regulatorily unattractive even if historical patent barriers had disappeared.

What was the financial trajectory of DARVON W/ ASA?

The product’s financial trajectory was a long decline rather than a late-stage growth story.

Early commercial phase

Darvon benefited from the expansion of prescription analgesic use in the second half of the twentieth century. The product was supported by brand recognition, physician familiarity, and the broad use of combination analgesics.

Mature and generic phase

As generic propoxyphene products became available, pricing and market share deteriorated. The product had limited differentiation from generic alternatives. Combination products also faced substitution from generic aspirin, acetaminophen, ibuprofen, and other pain treatments.

Pre-withdrawal phase

By the 2000s, safety concerns materially constrained the brand. Regulators required stronger warnings, and prescribing increasingly shifted toward alternatives. The product’s remaining revenue depended on legacy prescribing, not new therapeutic adoption.

Post-withdrawal phase

U.S. revenue fell to zero after the product was removed from distribution. Any residual international revenue was limited by European withdrawal actions and restrictions in other jurisdictions.

Public company filings did not generally disclose standalone revenue for DARVON W/ ASA. Available financial reporting typically grouped Darvon, Darvocet, or broader product portfolios within larger business segments. As a result, no reliable public revenue series isolates DARVON W/ ASA by year.

Financial phase	Revenue profile	Primary driver
Launch and expansion	Growing	Brand adoption and opioid analgesic demand
Mature brand	Stable to declining	Market saturation
Generic competition	Declining	Substitution and price erosion
Safety-warning period	Accelerating decline	Reduced prescribing and regulatory restrictions
Withdrawal period	Near-zero to zero in the U.S.	FDA action and market exit

How much revenue was exposed to DARVON W/ ASA?

Standalone revenue exposure cannot be established from public disclosures. The product was not normally reported as a separate material operating segment.

The economic exposure was limited by several factors:

• The active ingredient was generic and technologically mature.
• Multiple propoxyphene products competed for the same prescriptions.
• Combination analgesics had low switching costs.
• The product had no durable patent moat.
• Safety concerns reduced prescription volume before withdrawal.
• The product was not a biologic or specialty medicine with high per-patient revenue.

The primary financial consequences of withdrawal were more likely to involve inventory write-offs, discontinuation costs, regulatory expenses, legal exposure, and portfolio cleanup than the loss of a major growth asset.

Which companies challenged or competed with DARVON W/ ASA?

DARVON W/ ASA faced competition from both direct propoxyphene products and broader analgesic alternatives.

Direct competitors

• Generic propoxyphene hydrochloride products
• Darvon and Darvon Compound-65
• Darvocet-N and other propoxyphene-acetaminophen products
• Combination products marketed by other manufacturers

Therapeutic substitutes

• Aspirin and aspirin combinations
• Acetaminophen
• Ibuprofen and other NSAIDs
• Codeine combinations
• Hydrocodone combinations
• Tramadol
• Other short-acting opioid analgesics

The most important competitive threat was substitution, not a single branded challenger. Physicians could move patients to products with more familiar dosing, stronger evidence, or less concern about cardiac toxicity.

What patent protections covered DARVON W/ ASA?

DARVON W/ ASA did not retain an active patent estate capable of supporting premium pricing at the time of withdrawal.

Composition patents

Historical patents may have covered propoxyphene chemistry or related compounds, but those rights expired long before the product’s 2010 withdrawal.

Formulation patents

The aspirin-propoxyphene combination was a conventional oral dosage form. No publicly relevant, late-expiring formulation patent is associated with an ongoing commercial franchise.

Method-of-use patents

No active method-of-use patent created a meaningful barrier to generic or therapeutic substitution. The product was used for conventional analgesia rather than a newly patented disease indication.

Manufacturing and technical barriers

Manufacturing was not the principal barrier to competition. The product used established small-molecule chemistry and conventional oral manufacturing. Regulatory safety, rather than synthesis or formulation complexity, determined the product’s commercial fate.

Were there Paragraph IV challenges involving DARVON W/ ASA?

Paragraph IV litigation was not a material driver of the product’s final market history. By the time propoxyphene products were withdrawn, the core patent estate had expired or become commercially irrelevant.

A Paragraph IV certification can challenge an Orange Book-listed patent before its expiration. That mechanism has little practical value when:

• The relevant patents have expired.
• The reference product has been withdrawn.
• The FDA withdrawal is safety-related.
• A generic applicant lacks a commercially viable post-approval market.

The key risk to DARVON W/ ASA was therefore not patent invalidation. It was generic erosion followed by regulatory removal.

Did DARVON W/ ASA face biosimilar risk?

No. DARVON W/ ASA was a conventional small-molecule drug, not a biologic. It was exposed to generic-drug competition rather than biosimilar competition.

The relevant regulatory pathway was an abbreviated new drug application, or ANDA, rather than a biologics license application or biosimilar application. The product’s market risk came from therapeutic substitution and generic pricing pressure.

What litigation affected DARVON W/ ASA?

The principal legal exposure involved product liability and regulatory disputes relating to propoxyphene safety, rather than patent litigation.

Potential claims associated with propoxyphene products included allegations involving:

• Cardiac toxicity
• Overdose and death
• Inadequate warnings
• Failure to withdraw or restrict the product earlier
• Consumer and physician risk communication

The FDA’s 2010 action followed review of new cardiac safety data and a broader reassessment of the drug’s benefit-risk balance [1]. The European withdrawal recommendation reinforced the regulatory basis for market exit [2].

No active U.S. patent litigation is central to the current commercial analysis because the product is no longer marketed.

What licensing deals involved DARVON W/ ASA?

The product’s commercial history included changes in rights and marketing responsibility within the Darvon franchise. Eli Lilly was historically associated with Darvon, while Xanodyne Pharmaceuticals later marketed Darvon and Darvocet products in the United States.

Public disclosures do not establish a separate, product-level valuation for DARVON W/ ASA or a standalone royalty stream. The commercial rights were generally handled within broader product or portfolio arrangements. The 2010 FDA withdrawal eliminated the economic value of future U.S. commercialization rights.

How strong was the DARVON W/ ASA patent estate?

The patent estate was weak by modern pharmaceutical standards.

Patent-estate factor	Assessment
Active composition protection	None of practical commercial significance
Active formulation protection	No meaningful late-life barrier identified
Method-of-use protection	No material protection identified
Manufacturing complexity	Low
Generic substitution risk	High
Regulatory durability	Low
Post-withdrawal value	Negligible

The absence of biologic complexity, controlled-release technology, device integration, or a novel indication left the product exposed to generic competition. Its commercial life ended through regulatory action rather than patent expiration alone.

What generic launch scenarios existed for DARVON W/ ASA?

Before withdrawal, the likely generic scenario was continued price erosion and prescription migration. After withdrawal, the scenarios changed:

1. A generic manufacturer could attempt to maintain or obtain an approval for a propoxyphene product, but safety concerns would impair commercial viability.
2. A company could pursue a reformulated analgesic, but that would require new clinical and regulatory support.
3. Manufacturers could redirect demand to safer opioid or non-opioid alternatives.
4. A specialty relaunch would face substantial liability, regulatory, and reimbursement barriers.

The third scenario became the practical market outcome. Demand shifted to alternative analgesics rather than to a new entrant based on the DARVON W/ ASA formulation.

How did DARVON W/ ASA compare with modern analgesics?

Product category	Relative market position	Key advantage over DARVON W/ ASA
Acetaminophen	Broad first-line use	No opioid exposure
NSAIDs	Broad acute-pain use	Strong anti-inflammatory effect
Hydrocodone combinations	Higher-potency prescription analgesia	Greater analgesic efficacy
Tramadol	Intermediate prescription analgesia	Different mechanism and newer clinical positioning
Extended-release opioids	Chronic severe pain	Longer duration, although with substantial safety risks
DARVON W/ ASA	Obsolete	No durable clinical or commercial advantage

DARVON W/ ASA’s original middle-market position disappeared as physicians gained access to more standardized non-opioid and opioid options.

Key Takeaways

• DARVON W/ ASA was a legacy propoxyphene-and-aspirin analgesic.
• Its patent protection had expired or lost practical commercial value well before 2010.
• Generic competition and therapeutic substitution drove a long-term revenue decline.
• The FDA requested withdrawal of all U.S. propoxyphene products in November 2010 because cardiac and overdose risks outweighed benefits.
• European regulators had already recommended withdrawal in 2009.
• The product had generic risk, not biosimilar risk.
• No active patent litigation or meaningful Paragraph IV strategy defines the product today.
• Standalone product revenue was not separately disclosed in public filings.
• U.S. commercial revenue ended after withdrawal, with no credible relaunch pathway under the original formulation.
• The principal successor products were safer or more familiar analgesic alternatives, not direct branded replacements.

FAQs About DARVON W/ ASA

Is DARVON W/ ASA still available in the United States?

No. U.S. propoxyphene products, including Darvon-related products, were withdrawn after the FDA’s 2010 safety action.

What was the active ingredient in DARVON W/ ASA?

The product used propoxyphene hydrochloride with aspirin. Some related Darvon combination products also included caffeine, so product-specific labeling matters.

Why was DARVON W/ ASA discontinued?

The product was discontinued because propoxyphene was associated with serious cardiac electrical abnormalities, arrhythmias, overdose toxicity, and deaths. The FDA determined that the risks outweighed the benefits [1].

Was DARVON W/ ASA more commercially important than Darvocet?

Public disclosures do not provide reliable standalone revenue figures for either product. Darvocet generally had greater market recognition in the United States, but both products were affected by the broader decline and eventual withdrawal of propoxyphene medicines.

Can a generic manufacturer relaunch DARVON W/ ASA?

A relaunch under the original formulation would face major regulatory and liability barriers. Patent expiration would not solve the central problem because the product was withdrawn for safety reasons.

References

1. U.S. Food and Drug Administration. (2010, November 19). FDA drug safety communication: FDA recommends against the continued use of propoxyphene. https://www.fda.gov
2. European Medicines Agency. (2009). European Medicines Agency recommends withdrawal of propoxyphene-containing medicines. https://www.ema.europa.eu
3. U.S. Food and Drug Administration. (2011). Propoxyphene products withdrawn from the U.S. market. https://www.fda.gov
4. U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov