DARVON COMPOUND Drug Patent Profile

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

Darvon Compound is a drug marketed by Xanodyne Pharm and is included in one NDA.

The generic ingredient in DARVON COMPOUND is aspirin; caffeine; propoxyphene hydrochloride. There are twenty-two drug master file entries for this compound. Additional details are available on the aspirin; caffeine; propoxyphene hydrochloride profile page.

Summary for DARVON COMPOUND

US Patents:	0
Applicants:	1
NDAs:	1

US Patents and Regulatory Information for DARVON COMPOUND

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 COMPOUND	aspirin; caffeine; propoxyphene hydrochloride	CAPSULE;ORAL	010996-006	Mar 8, 1983		DISCN	No	No
Xanodyne Pharm	DARVON COMPOUND-65	aspirin; caffeine; propoxyphene hydrochloride	CAPSULE;ORAL	010996-007	Mar 8, 1983		DISCN	No	No

Darvon Compound Investment Analysis: Patent Status, FDA Withdrawal, Revenue Exposure, and Commercial Outlook

Last updated: July 31, 2026

Darvon Compound has no current investable commercial thesis. The product, a propoxyphene napsylate and acetaminophen combination, was withdrawn from the U.S. market after FDA concluded that propoxyphene increased the risk of serious and potentially fatal cardiac toxicity. FDA requested withdrawal of all propoxyphene-containing products in November 2010, and the withdrawal eliminated legitimate U.S. sales of Darvon Compound and related brands such as Darvocet.[1]

Darvon Compound is therefore a discontinued product, not an active pharmaceutical asset. Its current value is limited to historical brand recognition, legacy regulatory records, potential intellectual-property research, and litigation or liability analysis.

What is Darvon Compound and who marketed it?

Darvon Compound was an oral analgesic containing propoxyphene napsylate and acetaminophen. Historical formulations included Darvon Compound-65, which contained:

Attribute	Historical product information
Active opioid ingredient	Propoxyphene napsylate
Acetaminophen content	650 mg in the commonly marketed Compound-65 formulation
Therapeutic category	Prescription analgesic
Drug class	Opioid analgesic combination
U.S. regulatory status	Approved historically; withdrawn from the U.S. market
Current U.S. commercial status	Not marketed
Current investment status	No active product revenue thesis
Biosimilar relevance	None; this was a small-molecule drug
Controlled-substance history	Propoxyphene was federally scheduled as a Schedule IV substance before withdrawal

Propoxyphene was developed and commercialized historically by Eli Lilly and later marketed through other companies, including Xanodyne Pharmaceuticals. Product ownership, NDA sponsorship, and distribution arrangements changed over the drug’s commercial life. Those historical changes do not create a current operating opportunity because the U.S. product was removed from the market.

When did Darvon Compound lose exclusivity?

Darvon Compound lost practical commercial exclusivity through product withdrawal rather than through a conventional generic-entry cycle.

The FDA approved propoxyphene products decades before the modern Hatch-Waxman patent and exclusivity framework became central to pharmaceutical competition. Any original compound patents would have expired long before the FDA withdrawal in 2010. Historical formulation or method-of-use patents, if any remained in force during later commercialization, did not preserve the product after the FDA action.

Darvon Compound exclusivity timeline

Period	Event	Investment relevance
1950s	Propoxyphene introduced in the United States	Original composition-of-matter protection began historically
1970s and 1980s	Propoxyphene combination products commercialized broadly	Brand and generic competition developed
2000s	Safety concerns increased, including overdose and cardiac-risk concerns	Regulatory and liability risk grew
2009	European regulators recommended withdrawal of propoxyphene products	International commercial exposure declined
November 19, 2010	FDA requested withdrawal of all propoxyphene-containing products from the U.S. market	U.S. revenue opportunity ended
2011 onward	U.S. supply was removed and remaining inventory was eliminated	No legitimate U.S. launch opportunity

FDA stated that new data demonstrated a risk of serious cardiac toxicity, including changes in cardiac electrical activity, even at therapeutic doses. FDA concluded that the safety risks outweighed the drug’s limited effectiveness for pain management.[1]

What patents protect Darvon Compound?

No active, commercially material U.S. patent estate is associated with current Darvon Compound sales.

The relevant patent categories would historically have included:

1. Propoxyphene compound patents.
2. Propoxyphene salts, including the napsylate salt.
3. Combination formulations containing propoxyphene and acetaminophen.
4. Dosage and administration methods.
5. Manufacturing and pharmaceutical-composition claims.

Those categories do not establish a present investment opportunity. The product’s original chemical protection expired long before the FDA withdrawal. Any later patent rights would have required enforceable claims covering a specific formulation, manufacturing process, or use. Such claims could not overcome the market withdrawal without a new FDA-approved product and a lawful commercial channel.

Orange Book status

Darvon Compound does not have a current Orange Book commercial listing that supports an active branded-product exclusivity thesis. The Orange Book is relevant to approved prescription drug products and their patent certifications, but a withdrawn product does not create a viable Paragraph IV launch pathway.

A potential applicant could theoretically pursue a new application or seek approval for a different propoxyphene product. That would require overcoming the underlying safety findings, obtaining FDA approval, and satisfying controlled-substance and risk-management requirements. A conventional generic strategy is commercially and regulatorily unattractive.

Why was Darvon Compound withdrawn by FDA?

FDA required withdrawal because propoxyphene was associated with dose-dependent cardiac toxicity. The agency cited electrocardiogram changes, including prolongation of the QT interval, widening of the QRS complex, and prolongation of the PR interval.[1]

The risk was commercially important for four reasons:

• The toxicity could occur at doses used for ordinary pain treatment.
• Accidental and intentional overdose could produce fatal arrhythmias.
• Acetaminophen combination products created an additional risk of hepatic injury when patients exceeded recommended doses.
• The drug offered limited incremental benefit compared with alternative analgesics.

FDA’s action applied to all propoxyphene-containing products marketed in the United States, including Darvon, Darvon Compound, Darvocet, and related generic products.[1]

What is the current FDA regulatory status of Darvon Compound?

Darvon Compound is not an active U.S. commercial product. FDA’s 2010 action removed propoxyphene products from the U.S. market. The withdrawal was based on safety, not on a routine commercial discontinuation.

This distinction matters for valuation. A discontinued product with ordinary patent expiry may retain residual value through authorized generic supply, licensing, or reformulation. A product removed because of serious cardiac toxicity has a materially different risk profile. Reintroduction would require a new regulatory strategy and compelling evidence that the risk-benefit balance had changed.

There is no established FDA pathway that would allow a company to relaunch the original Darvon Compound product simply by relying on its historical approval.

Are there Paragraph IV challenges involving Darvon Compound?

No current Paragraph IV challenge represents a meaningful investment catalyst for Darvon Compound.

Paragraph IV litigation generally occurs when a generic applicant challenges listed patents for an approved reference drug. Darvon Compound’s original patent life expired long ago, and the product was withdrawn from the U.S. market. The more important barrier is FDA safety status, not patent enforcement.

A generic applicant would face several problems:

Issue	Effect on a generic launch
Product withdrawal	Reference-product and regulatory pathway complications
Cardiac toxicity	Substantial FDA approval risk
Limited medical use	Weak commercial demand
Opioid controls	Distribution, monitoring, and compliance burden
Acetaminophen exposure	Additional safety concern
Established substitutes	Weak pricing power and limited prescriber demand
Liability exposure	Elevated litigation and insurance costs

Patent litigation would therefore be secondary to regulatory and product-liability risk.

What patent litigation and settlements affected Darvon Compound?

The principal legal exposure surrounding Darvon Compound and related propoxyphene products involved safety, labeling, injury, and product-liability claims rather than modern patent disputes.

The FDA withdrawal followed a long period of regulatory scrutiny. Propoxyphene products were associated with reports of overdose, misuse, accidental death, and cardiac events. In the United States, manufacturers and marketers faced litigation concerning warnings, adequacy of labeling, and alleged failure to communicate risks.

No current patent settlement appears to create a commercial launch right or protect a revived Darvon Compound franchise. Historical settlements, if any, would need to be evaluated as liability records rather than as assets supporting future revenue.

How strong is the Darvon Compound patent estate?

The patent estate is commercially weak for four reasons.

Chemical claims are obsolete

The active ingredient is an old small molecule. Any original composition-of-matter patents expired decades ago. No new chemical entity exclusivity remains.

Formulation claims have limited value

A formulation patent covering propoxyphene and acetaminophen would face both expiration risk and regulatory obsolescence. Even an unexpired formulation claim would not authorize sale of a product that FDA removed for safety reasons.

Method-of-use claims do not solve the safety problem

A narrow method-of-use patent could theoretically cover a defined patient population or dosing method. Such protection would have limited value unless FDA accepted the use and the risk-benefit profile. The fundamental cardiac-safety finding weakens the commercial relevance of any historical use patent.

Manufacturing claims are not sufficient

A process patent could protect a particular synthesis or formulation method, but it would not create demand for the product. Propoxyphene chemistry is mature, and alternative manufacturing routes would likely be available.

Is Darvon Compound a generic, biosimilar, or specialty-drug opportunity?

Darvon Compound is a small-molecule opioid combination product, not a biologic. Biosimilar risk is therefore irrelevant. The relevant competitive categories are generic analgesics, non-opioid pain medicines, and alternative opioid products.

Competitive products

At the time of withdrawal, patients and prescribers could use alternatives such as:

• Acetaminophen alone.
• Nonsteroidal anti-inflammatory drugs.
• Tramadol.
• Hydrocodone-acetaminophen combinations.
• Oxycodone-acetaminophen combinations.
• Other opioid and non-opioid pain therapies.

The competitive landscape has become more difficult since 2010 because opioid prescribing is subject to tighter controls, prescription-monitoring requirements, abuse-deterrence policies, and heightened liability scrutiny.

What generic launch risks exist for Darvon Compound?

A generic launch would face a high probability of regulatory failure or commercial underperformance.

The product would need to address the same safety findings that caused the withdrawal. A company could not rely on ordinary ANDA economics because the reference product is no longer a viable marketed standard. A new NDA, clinical development program, or substantial safety justification could be required, depending on the proposed regulatory route.

Commercial launch risks include:

• FDA refusal based on cardiac risk.
• Difficulty obtaining acceptable labeling.
• Controlled-substance compliance costs.
• Limited payer and prescriber acceptance.
• Product-liability claims.
• Distribution restrictions.
• Low expected volume.
• Competition from safer alternatives.

The expected return would not justify conventional generic development spending.

What are the revenue and investment fundamentals?

Darvon Compound has no current branded revenue stream that can support valuation. The product was withdrawn more than a decade ago, and the original commercial franchise is inactive.

Investment-fundamentals scorecard

Factor	Assessment
Current revenue	None from legitimate U.S. Darvon Compound sales
Revenue growth	Not applicable
Gross-margin potential	Not investable without regulatory re-entry
Patent exclusivity	Expired or commercially irrelevant
FDA status	Withdrawn from the U.S. market
Generic competition	Historically extensive; current launch economics weak
Biosimilar threat	Not applicable
Manufacturing barrier	Low to moderate; chemistry is mature
Regulatory barrier	Very high
Liability risk	High
Licensing value	Minimal absent a new safety and regulatory strategy
Strategic value	Limited to legacy rights, data, or litigation portfolios

A company holding historical Darvon-related rights would not merit valuation based on product revenue unless it had a separate, documented program involving a new molecule, new indication, or materially different delivery system. The legacy product itself does not provide a credible growth asset.

Could a new formulation revive Darvon Compound?

A new formulation would not automatically restore commercial value.

Possible technical approaches could include abuse-deterrent delivery, modified release, lower-dose administration, or a formulation designed to reduce peak exposure. Each would face major obstacles:

1. The cardiac toxicity associated with propoxyphene is not necessarily solved by changing release kinetics.
2. Acetaminophen toxicity remains relevant in combination products.
3. FDA would likely require a persuasive clinical and pharmacologic rationale.
4. A reformulated product would need new regulatory support.
5. Physicians and payers could remain unwilling to use the active ingredient.

A new formulation might generate patentable subject matter, but patentability would not equal commercial viability. The safety profile would remain the central issue.

What geographic markets remain relevant?

The United States is closed to ordinary Darvon Compound commercialization following the FDA withdrawal. European regulators also acted against propoxyphene-containing products, with the European Medicines Agency recommending withdrawal in 2009 because the risks outweighed the benefits.[2]

Other countries have applied different regulatory approaches to propoxyphene products. Any remaining non-U.S. rights would require country-specific confirmation of:

• Marketing authorization.
• Product registration.
• Patent status.
• Controlled-substance classification.
• Local safety restrictions.
• Current distribution rights.

Historical international availability does not create a reliable global investment thesis. The product’s safety profile and declining clinical role would remain material constraints.

What licensing deals could create value?

A Darvon Compound licensing deal would have limited standalone value. Potentially licensable assets could include:

• Historical regulatory files.
• Manufacturing know-how.
• Trademark rights.
• Litigation records.
• Legacy pharmacovigilance data.
• Rights to a substantially redesigned delivery system.

A license limited to the old product, brand, or expired patents would have little economic value. A credible deal would require a new active development program, a differentiated formulation, or rights in a market where propoxyphene remains legally approved and commercially relevant.

What is the likely generic launch scenario?

The most likely scenario is no legitimate U.S. generic relaunch.

Scenario	Probability assessment	Economic result
Conventional ANDA launch	Low	Regulatory and reference-product barriers
New NDA for original formulation	Low	High safety and clinical-development burden
Reformulated propoxyphene product	Low	Uncertain benefit and high FDA scrutiny
Limited foreign-market supply	Market-specific	Potentially small, declining revenue
Continued U.S. commercial absence	High	No product revenue
Litigation or legacy-rights monetization	Limited	Non-recurring or low-value proceeds

Key Takeaways

• Darvon Compound is a discontinued propoxyphene napsylate and acetaminophen product.
• FDA requested withdrawal of all U.S. propoxyphene products in November 2010 because of serious cardiac toxicity.[1]
• Original chemical patents expired long before withdrawal.
• No active Orange Book or Paragraph IV strategy creates a meaningful current investment catalyst.
• Biosimilar analysis does not apply because Darvon Compound is a small-molecule drug.
• A new formulation would require a new regulatory and clinical rationale, not merely a patent filing.
• Current revenue exposure is effectively zero for legitimate U.S. sales.
• The main barriers are FDA safety concerns, liability risk, controlled-substance obligations, and weak demand.
• Darvon Compound does not support a conventional pharmaceutical investment thesis.

FAQs

Is Darvon Compound still available by prescription?

No. Darvon Compound was withdrawn from the U.S. market after FDA required removal of propoxyphene-containing products in 2010.

Does Darvon Compound have an active patent?

No commercially relevant active patent estate supports current U.S. Darvon Compound sales. The drug’s original chemical protection expired decades ago.

Can a generic company launch Darvon Compound?

A conventional generic launch is unlikely to be commercially or regulatorily viable because FDA removed the product for safety reasons and the reference product is no longer actively marketed.

Is Darvon Compound related to Darvocet?

Yes. Both products contained propoxyphene. Darvocet also included acetaminophen, while Darvon referred primarily to propoxyphene products. FDA’s 2010 action covered propoxyphene-containing products broadly.

What is the investment value of the Darvon brand?

The brand has little standalone value. Any residual value would depend on specific foreign rights, historical data, trademarks, or a new product program that addresses the active ingredient’s safety risks.

References

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

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. (2010). FDA drug safety communication: FDA recommends against continued use of propoxyphene. https://www.fda.gov

4. U.S. National Library of Medicine. (n.d.). Propoxyphene and acetaminophen drug information. MedlinePlus. https://medlineplus.gov/druginfo/meds/a601007.html