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: PATENT LANDSCAPE AND INVESTMENT FUNDAMENTALS ANALYSIS

Last updated: February 17, 2026

Darvon Compound (propoxyphene), a prescription analgesic, presents a complex investment scenario driven by evolving patent exclusivity, regulatory scrutiny, and market dynamics. While its primary patent protection has long expired, a review of associated intellectual property, manufacturing processes, and potential future patent filings is crucial for assessing ongoing market viability and competitive positioning.

WHAT IS THE CORE INTELLECTUAL PROPERTY LANDSCAPE FOR DARVON COMPOUND?

The foundational patent for propoxyphene hydrochloride, the active pharmaceutical ingredient in Darvon Compound, expired decades ago. United States Patent 2,811,526, filed by Eli Lilly and Company in 1955 and granted in 1957, covered the compound itself. This means the basic chemical entity is in the public domain, allowing for generic manufacturing and marketing.

However, secondary patents and formulations may have provided extended protection or market advantages. These can include:

• Formulation Patents: Patents covering specific dosage forms, controlled-release mechanisms, or combinations with other active ingredients. For example, a patent might cover a specific tablet composition that improves bioavailability or patient compliance.
• Process Patents: Patents protecting novel or improved methods of synthesizing propoxyphene or its salts. If a manufacturer develops a more efficient or cost-effective synthesis, this can create a temporary competitive edge, even if the compound itself is off-patent.
• Polymorph Patents: Patents that claim specific crystalline forms (polymorphs) of the active pharmaceutical ingredient. Different polymorphs can exhibit distinct physical properties such as solubility, stability, and manufacturability, which can be patentable.
• Combination Therapy Patents: Patents covering the use of propoxyphene in combination with other drugs for specific therapeutic indications.

Identifying these secondary patents and their expiration dates is critical for understanding the remaining legal barriers to entry for potential competitors or the scope of protection for existing manufacturers. The absence of robust, active secondary patent protection directly impacts the competitive landscape and pricing power.

WHAT ARE THE HISTORICAL SALES AND MARKET POSITIONING OF DARVON COMPOUND?

Darvon Compound was historically a significant player in the pain management market. Developed by Eli Lilly and Company, it was marketed as an effective analgesic for mild to moderate pain.

• Peak Sales: While specific peak annual sales figures are not readily available due to the proprietary nature of historical pharmaceutical data and the long period since its peak market presence, Darvon Compound and its related products (including Darvocet, a combination product with acetaminophen) were widely prescribed and generated substantial revenue for Eli Lilly for many years.
• Market Share: At its zenith, Darvon Compound held a considerable share of the non-narcotic analgesic market, often competing with over-the-counter options like ibuprofen and naproxen, as well as other prescription pain relievers.
• Therapeutic Niche: Its primary niche was for patients who required prescription-strength pain relief but for whom opioids might be considered too potent or have a higher risk of abuse.

The market position of Darvon Compound has been significantly eroded by several factors, including the development of newer analgesics, concerns regarding its safety profile, and regulatory actions.

WHAT ARE THE REGULATORY AND SAFETY CONCERNS SURROUNDING DARVON COMPOUND?

Regulatory actions and safety concerns have profoundly impacted Darvon Compound's market presence and availability.

• Cardiotoxicity Risks: The primary concern has been the association of propoxyphene with cardiac arrhythmias, particularly QT interval prolongation and Torsades de Pointes. Studies indicated a potential for serious cardiac events, especially at higher doses or in individuals with pre-existing cardiac conditions.
• FDA Actions:
  • In November 2010, the U.S. Food and Drug Administration (FDA) requested that its manufacturer voluntarily withdraw propoxyphene-containing products from the U.S. market due to safety concerns, specifically citing the cardiac risks.
  • Following the FDA's request, Eli Lilly and Company announced in November 2010 that it would cease marketing Darvon and Darvocet in the United States.
  • In March 2011, the European Medicines Agency (EMA) also recommended the suspension of marketing authorizations for propoxyphene-containing medicines across the European Union due to safety concerns.
• Withdrawal from Market: As a result of these regulatory pressures and voluntary actions by manufacturers, Darvon Compound and its combination products (like Darvocet) have been largely withdrawn from major markets, including the United States and the European Union.
• Abuse Potential: Like other opioid analgesics, propoxyphene also carries a risk of abuse, misuse, and addiction, though generally considered lower than more potent opioids.

These regulatory decisions and safety advisories have effectively removed Darvon Compound as a significant therapeutic option in many regions, drastically limiting its market potential.

WHAT ARE THE CURRENT MANUFACTURING AND SUPPLY CHAIN CONSIDERATIONS?

The manufacturing and supply chain for Darvon Compound are significantly impacted by its market withdrawal.

• Limited Current Production: Due to the voluntary market withdrawal in key regions like the U.S. and EU, large-scale, commercial manufacturing of Darvon Compound for these markets has ceased.
• Generic Availability: While the base compound is off-patent, the lack of a significant market in major developed countries means there is minimal incentive for generic manufacturers to maintain or initiate production for these regions.
• Niche Markets: Production may persist for specific, smaller markets where propoxyphene has not been withdrawn or for investigational purposes, but this would involve specialized contract manufacturing organizations (CMOs).
• Raw Material Sourcing: If any production were to resume, sourcing of propoxyphene base and excipients would be a critical consideration. Given the reduced demand, suppliers of key intermediates might have shifted production or discontinued their availability.
• Regulatory Compliance: Any entity considering manufacturing propoxyphene would need to navigate stringent current Good Manufacturing Practices (cGMP) regulations. The historical safety concerns would also likely lead to heightened regulatory scrutiny.

The current manufacturing and supply chain landscape indicates that re-establishing production at a significant scale would involve overcoming substantial hurdles, including market demand, regulatory approvals, and establishing reliable raw material sources.

WHAT IS THE COMPETITIVE LANDSCAPE FOR ANALGESICS WHERE DARVON COMPOUND ONCE COMPETED?

The analgesic market is highly competitive and has evolved significantly since Darvon Compound's peak.

• Over-the-Counter (OTC) Analgesics: This segment is dominated by acetaminophen (e.g., Tylenol), ibuprofen (e.g., Advil, Motrin), and naproxen sodium (e.g., Aleve). These are widely available, inexpensive, and generally considered safe for short-term use when used as directed.
• Prescription Non-Opioids: This category includes non-steroidal anti-inflammatory drugs (NSAIDs) like diclofenac, celecoxib (a COX-2 inhibitor), and topical analgesics.
• Prescription Opioids:
  • Weak Opioids: While propoxyphene was in this category, other options have emerged or gained prominence, often with perceived better safety profiles or efficacy. Tramadol, for instance, is a synthetic opioid that also acts as a serotonin-norepinephrine reuptake inhibitor (SNRI) and has its own set of regulatory considerations.
  • Strong Opioids: Hydrocodone, oxycodone, morphine, fentanyl, and hydromorphone are used for moderate to severe pain. This class of drugs is under intense scrutiny due to the opioid crisis, leading to tighter prescribing regulations and a drive towards non-opioid alternatives.
• Adjuvant Therapies: Drugs targeting neuropathic pain, such as gabapentinoids (gabapentin, pregabalin) and certain antidepressants (SNRIs, TCAs), have become standard treatments for specific pain conditions.
• Non-Pharmacological Treatments: Increased emphasis is placed on physical therapy, exercise, psychological interventions, and interventional pain management techniques.

The current competitive landscape strongly favors alternatives with demonstrably better safety profiles, broader therapeutic applications, or novel mechanisms of action. The historical safety concerns associated with propoxyphene make it difficult to compete against established OTC drugs and newer prescription agents with more favorable risk-benefit ratios.

WHAT ARE THE POTENTIAL FUTURE R&D OR INVESTMENT OPPORTUNITIES RELATED TO PROPOXYPHENE?

Given the historical context and current regulatory status, direct R&D or investment in Darvon Compound itself for its original indications is highly unlikely to be viable. However, tangential opportunities or lessons learned could exist:

• Metabolism and Toxicology Research: Further research into the specific metabolic pathways and toxicological mechanisms of propoxyphene could yield insights applicable to other drugs with similar chemical structures or metabolic profiles. This is more academic than commercial.
• Repurposing in Highly Controlled Settings: Hypothetically, if a specific subpopulation or a rare pain indication were identified where propoxyphene offered a unique benefit not met by current therapies, and if the risks could be meticulously managed through extreme clinical control (e.g., in-patient monitoring), a highly niche application might be conceived. However, this is speculative and faces immense regulatory hurdles.
• Development of Safer Analogues: The identification of propoxyphene's safety liabilities could inform the design of novel analgesic compounds that retain some beneficial properties (e.g., mild opioid activity without certain toxicophores) but with significantly improved safety profiles. This represents an R&D opportunity in the broader analgesic space, not for Darvon Compound itself.
• Generic Manufacturing Strategy for Underserved Markets: If specific markets exist where Darvon Compound has not been withdrawn and generic production is still permitted, a focused strategy on supplying those niche regions with cost-effective generics could be explored, contingent on navigating local regulatory pathways. This would require deep market intelligence on drug approvals and demand outside major Western markets.

Any investment or R&D strategy involving propoxyphene would need to acknowledge and address the significant historical safety and regulatory challenges. The primary value proposition for propoxyphene has been irrevocably altered by these factors.

KEY TAKEAWAYS

Darvon Compound's intellectual property foundation, primarily the expired patent for propoxyphene hydrochloride, renders the active pharmaceutical ingredient generic. While secondary patents on formulations or manufacturing processes may have existed, their impact is largely diminished due to significant regulatory actions. Historically a prominent analgesic, its market position has been decimated by U.S. FDA and European Medicines Agency requests for withdrawal stemming from cardiotoxicity risks. This has led to market removal in major Western economies, effectively ceasing large-scale manufacturing and supply for these regions. The highly competitive analgesic market, now prioritizing drugs with superior safety profiles and novel mechanisms, offers little space for propoxyphene. Consequently, direct investment in Darvon Compound for its original indications is not a viable strategy. Future considerations would be limited to highly speculative, niche applications or research into its toxicological mechanisms, rather than commercial product development.

FREQUENTLY ASKED QUESTIONS

1. Has the original patent for Darvon Compound expired? Yes, the fundamental patent for propoxyphene hydrochloride expired decades ago, making the active pharmaceutical ingredient a generic substance.

2. Are there any current regulatory approvals for Darvon Compound in major markets like the U.S. or EU? No, Darvon Compound and related products have been largely withdrawn from major markets, including the U.S. and EU, due to significant safety concerns, particularly cardiotoxicity.

3. What are the primary safety concerns associated with propoxyphene? The primary safety concerns involve the potential for serious cardiac arrhythmias, including QT interval prolongation and Torsades de Pointes, especially at higher doses or in patients with pre-existing cardiac conditions.

4. Is there a market for generic Darvon Compound products? Due to the market withdrawals in major Western economies, there is minimal current demand or incentive for generic manufacturers to produce Darvon Compound for these regions. Niche markets outside these regions may exist.

5. What is the most plausible future scenario for propoxyphene-related intellectual property or investment? The most plausible future scenario is not direct investment in Darvon Compound, but rather potential research into its toxicological mechanisms, or the development of safer analgesic analogues informed by its liabilities. Any direct commercial interest would face extreme regulatory and market entry challenges.

CITATIONS

[1] U.S. Food and Drug Administration. (2010, November 22). FDA requests voluntary withdrawal of propoxyphene. [Press release]. Retrieved from https://www.fda.gov/drugs/drug-safety-and-availability/fda-requests-voluntary-withdrawal-propoxyphene [2] European Medicines Agency. (2011, March 17). European Medicines Agency recommends suspension of propoxyphene-containing medicines. [Press release]. Retrieved from https://www.ema.europa.eu/en/news/european-medicines-agency-recommends-suspension-propoxyphene-containing-medicines [3] United States Patent 2,811,526. (1957). Esters of dialkylaminoalkyl-substituted phenylacetic acids. Eli Lilly and Company.