Phenindione - Generic Drug Details

What are the generic drug sources for phenindione and what is the scope of freedom to operate?

Phenindione is the generic ingredient in one branded drug marketed by Sanofi Aventis Us and is included in one NDA. Additional information is available in the individual branded drug profile pages.

Summary for phenindione

US Patents:	0
Tradenames:	1
Applicants:	1
NDAs:	1
Raw Ingredient (Bulk) Api Vendors:	90
Clinical Trials:	4
DailyMed Link:	phenindione at DailyMed

Recent Clinical Trials for phenindione

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

Sponsor	Phase
University of Edinburgh	Phase 3
NHS Lothian	Phase 3
Chiltern International Inc.	Phase 3

See all phenindione clinical trials

Medical Subject Heading (MeSH) Categories for phenindione

Anticoagulants

Anatomical Therapeutic Chemical (ATC) Classes for phenindione

B01AA	Vitamin K antagonists
B01A	ANTITHROMBOTIC AGENTS
B01	ANTITHROMBOTIC AGENTS
B	Blood and blood forming organs

US Patents and Regulatory Information for phenindione

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Sanofi Aventis Us	HEDULIN	phenindione	TABLET;ORAL	008767-002	Approved Prior to Jan 1, 1982		DISCN	No	No

Phenindione Market Dynamics, Financial Trajectory, Patents, and Commercial Outlook

Last updated: September 2, 2026

Phenindione has no meaningful modern pharmaceutical market. The oral anticoagulant was displaced by warfarin because of serious hematologic and hepatic toxicity, then by direct oral anticoagulants such as apixaban and rivaroxaban. Phenindione is not an active commercial growth product, has no identifiable U.S. Orange Book franchise, and has no material remaining composition-of-matter patent value. Its financial trajectory is best characterized as historical decline followed by commercial obsolescence.

What is phenindione and how was it used?

Phenindione is an oral vitamin K antagonist anticoagulant in the indandione class. It reduces synthesis of vitamin K-dependent clotting factors and was used historically for thromboembolic disease, including prevention of systemic embolism and treatment of venous thromboembolism.

Its commercial positioning deteriorated because of adverse reactions that included:

• Agranulocytosis and other blood dyscrasias
• Thrombocytopenia
• Hepatotoxicity
• Hypersensitivity reactions
• Bleeding associated with anticoagulant activity

Phenindione was marketed historically under names including Dindevan. Clinical practice moved toward warfarin, which offered a more established monitoring framework and broader regulatory acceptance. Later, direct oral anticoagulants captured substantial share in atrial fibrillation and venous thromboembolism.

Historical pharmacology and competitive position

Phenindione and warfarin both require coagulation monitoring, but phenindione did not achieve warfarin's durability as a standard anticoagulant. The indandione class became commercially unattractive as safer or better-supported alternatives gained adoption.

Product	Class	Historical or current status	Commercial position
Phenindione	Indandione vitamin K antagonist	Historical, largely discontinued	No meaningful current market
Warfarin	Coumarin vitamin K antagonist	Widely marketed	Generic, established standard
Apixaban	Direct factor Xa inhibitor	Actively marketed	Major branded and generic-transition market
Rivaroxaban	Direct factor Xa inhibitor	Actively marketed	Major branded and generic-transition market
Dabigatran	Direct thrombin inhibitor	Actively marketed in selected markets	Smaller DOAC segment
Edoxaban	Direct factor Xa inhibitor	Actively marketed in selected markets	Regional commercial presence

When did phenindione lose exclusivity and commercial relevance?

Phenindione lost practical exclusivity decades ago. Its underlying active ingredient dates to the mid-20th century, placing any original composition-of-matter protection well beyond the ordinary patent term.

The commercially important event was not patent expiry. It was therapeutic displacement.

Period	Market development	Financial effect
1940s-1960s	Phenindione used as an oral anticoagulant	Initial product adoption
1960s-1980s	Warfarin became the preferred vitamin K antagonist in many markets	Progressive share loss
1980s-2000s	Safety concerns and limited clinical utility reduced use	Commercial contraction
2010s	DOACs expanded in atrial fibrillation and venous thromboembolism	Further loss of anticoagulant relevance
Current market	No material branded phenindione franchise identified	Revenue effectively negligible

No economically relevant patent-expiration event is likely to create a generic-entry opportunity because the product itself is already commercially obsolete in major regulated markets.

What patents protect phenindione?

No active, commercially meaningful patent estate is associated with phenindione as an established drug product.

Composition-of-matter patents

Any original active-ingredient patent rights would have expired many decades ago. Modern patent protection for phenindione is unlikely to exist because:

1. The active compound is old.
2. Its core pharmacology is established.
3. There is no significant current development program requiring new exclusivity.
4. Historical formulations would generally be vulnerable to prior-art challenges.

Formulation patents

No material active formulation franchise is publicly associated with phenindione. A theoretical new patent could cover a novel formulation, delivery system, combination, or manufacturing process, but such protection would not restore commercial value without regulatory redevelopment and a clinically differentiated product.

Method-of-use patents

No current high-value method-of-use patent position is associated with phenindione. Historical anticoagulation uses are part of the public domain and would not support a modern exclusivity strategy.

Manufacturing and process barriers

Manufacturing is unlikely to be the principal barrier. Phenindione is a small-molecule chemical compound, not a biologic requiring complex cell-line, purification, or cold-chain infrastructure. The principal barriers are:

• Regulatory reactivation
• Clinical safety evidence
• Physician acceptance
• Availability of established alternatives
• Limited commercial demand
• Potential pharmacovigilance exposure

What is the Orange Book status of phenindione?

Phenindione does not have a meaningful U.S. Orange Book position. The product is not recognized as a current U.S. branded reference-product franchise with active listed patents or regulatory exclusivity.

That has several consequences:

• There is no active Orange Book patent-listing strategy.
• There is no economically important Paragraph IV target.
• There is no evident U.S. brand-generic litigation platform.
• A potential sponsor would likely face regulatory redevelopment rather than ordinary abbreviated generic competition.

The absence of an Orange Book franchise does not necessarily establish that no historical U.S. product ever existed. It indicates that phenindione does not function as a current U.S. reference product with a commercially relevant listed patent estate.

Are there Paragraph IV challenges to phenindione?

No material contemporary Paragraph IV challenge is associated with phenindione.

Paragraph IV litigation normally arises when an ANDA applicant challenges patents listed for an active reference drug. Phenindione lacks the commercial conditions that usually produce such disputes:

• No major branded reference product
• No active Orange Book patent portfolio
• No large prescription market
• No meaningful exclusivity period to attack
• No significant expected return on generic litigation

A future applicant would face a regulatory and market-access problem, not a conventional patent challenge against an incumbent phenindione manufacturer.

What is the FDA regulatory status of phenindione?

Phenindione is not a current mainstream FDA-approved anticoagulant in the U.S. market. It is absent from contemporary anticoagulation practice and is not positioned as an active FDA-regulated commercial product comparable with warfarin or the DOACs.

The regulatory distinction matters:

Regulatory issue	Phenindione position
Current U.S. branded product	Not identified as a material commercial product
Orange Book franchise	No meaningful current listing
Active FDA exclusivity	None of commercial significance
ANDA competition	No material active market
NDA litigation	No material contemporary activity
Clinical guideline role	Not a standard recommended anticoagulant
Biosimilar pathway	Not applicable

Any attempt to reintroduce phenindione would likely require a regulatory strategy closer to redevelopment of an obsolete or inadequately supported drug than a conventional generic launch.

How strong is the phenindione patent estate?

The patent estate is commercially weak to nonexistent.

Patent category	Likely status	Business significance
Original compound patent	Expired	No exclusivity
Historical formulation patents	Expired or commercially irrelevant	No durable barrier
Method-of-use patents	No meaningful current position identified	No protected indication
Manufacturing patents	No known material barrier	Limited defensive value
New formulation opportunity	Theoretically possible	Would require new development and clinical justification

Patent strength is therefore not the main determinant of phenindione's value. The decisive issues are clinical utility, regulatory status, safety, and demand.

What patent litigation affects phenindione?

No significant current patent litigation affects phenindione.

The product has no visible litigation pattern involving:

• ANDA Paragraph IV claims
• Patent-infringement suits
• Hatch-Waxman settlement agreements
• Licensing disputes
• Inter partes review proceedings
• Biosimilar litigation
• Patent-term-extension disputes

This absence reflects market inactivity rather than patent strength. There is little economic incentive to litigate over a product with no substantial branded revenue base.

Is phenindione affected by biosimilar risk?

No. Biosimilar risk is not applicable because phenindione is a chemically synthesized small molecule, not a biologic.

The relevant competitive risks are generic substitution and therapeutic substitution. Therapeutic substitution has already occurred at scale:

• Warfarin replaced much of the historical vitamin K antagonist use.
• Apixaban and rivaroxaban expanded the DOAC segment.
• Low-molecular-weight heparins and injectable anticoagulants retained roles in specific clinical settings.

What companies are challenging phenindione?

No major company is publicly identified as challenging a current phenindione franchise. There is no active competitive field comparable with the patent contests surrounding high-revenue anticoagulants.

Potential supply, if any, would more likely involve:

• Small-volume specialty manufacturers
• Regional suppliers
• Hospital or pharmacy compounding channels
• Legacy-market distributors

These channels do not create a conventional branded pharmaceutical market.

What is the financial trajectory for phenindione?

Phenindione has no identifiable current revenue stream of material size in public pharmaceutical-company reporting. Public companies generally do not disclose meaningful phenindione revenue because the drug is not a core commercial product.

Revenue trajectory

The financial profile follows a four-stage pattern:

1. Initial commercialization: Revenue was generated through historical oral anticoagulant use.
2. Therapeutic substitution: Warfarin captured physician preference and broader market use.
3. Safety-driven decline: Adverse-event concerns weakened demand.
4. Commercial disappearance: DOACs and generic anticoagulants removed the remaining economic rationale.

A precise global revenue figure is not available because historical sales were fragmented by country, brand, distributor, and product withdrawal date. Current revenue should be treated as negligible relative to active anticoagulant products.

Financial comparison with current anticoagulants

Product	Current commercial scale	Revenue model	Competitive status
Phenindione	Negligible	Legacy or limited regional supply	Commercially obsolete
Warfarin	Large generic-volume market	Low unit price, high prescription volume	Mature and durable
Apixaban	Large branded and generic-transition market	Premium anticoagulant pricing	Strong clinical adoption
Rivaroxaban	Large branded and generic-transition market	Premium anticoagulant pricing	Strong clinical adoption
Dabigatran	Moderate, region-dependent	Branded and generic sales	Established DOAC
Edoxaban	Regional	Branded sales in selected markets	Narrower geographic position

Phenindione has no credible route to compete on price, convenience, safety, evidence, or reimbursement against these products.

What generic launch risks exist for phenindione?

A hypothetical phenindione generic would face low patent risk but high commercial and regulatory risk.

Patent risk

Patent barriers would likely be minimal. The active ingredient is old, and no material current patent estate is evident.

Regulatory risk

Regulatory risk would be substantial because a sponsor may need to address:

• Current safety characterization
• Product quality and impurity controls
• Bioequivalence expectations
• Historical adverse-event evidence
• Labeling and clinical positioning
• Availability of a suitable reference product
• Market-specific approval requirements

Commercial risk

Commercial risks would be greater than patent risks:

• Limited prescribing demand
• Strong physician preference for alternatives
• Weak payer incentive to reimburse an obsolete product
• Potential liability from known toxicities
• Limited clinical-trial return on investment
• Difficulty securing distribution and pharmacovigilance infrastructure

The most plausible launch model would be a narrow, low-volume supply strategy in a jurisdiction where the product retains a recognized regulatory pathway or unmet local demand. A broad multinational launch is commercially implausible.

What licensing deals involve phenindione?

No material recent licensing deal involving phenindione is publicly established.

A licensing transaction would have limited strategic value unless it included a new asset, such as:

• A reformulated dosage form
• A controlled-release delivery system
• A combination product
• A new anticoagulation indication
• A validated safety improvement
• A manufacturing-cost advantage

Without such differentiation, licensing phenindione would transfer regulatory and liability obligations without creating a defensible revenue opportunity.

What geographic markets could support phenindione?

Phenindione's remaining opportunity, if any, is regional rather than global.

Geography	Commercial outlook
United States	No meaningful current market position
European Union	No mainstream clinical or commercial role
United Kingdom	Historical association with Dindevan, but no modern strategic franchise
Japan	No material current commercial position identified
Emerging markets	Possible limited legacy or local supply, but demand is uncertain
Hospital compounding channels	Potentially niche and low volume

Geographic availability should not be confused with commercial viability. A product may remain listed in an old database or appear through a limited distributor while generating little revenue.

How does phenindione compare with warfarin and DOACs?

Phenindione is inferior as a commercial asset across the main value drivers.

Value driver	Phenindione	Warfarin	DOACs
Patent value	None of practical significance	Expired	Historically strong, varying by product
Regulatory support	Limited or absent	Extensive	Extensive
Clinical familiarity	Historical	High	High and increasing
Monitoring burden	High	High	Lower for routine use
Safety perception	Weak	Established but narrow therapeutic index	Generally stronger in approved uses
Market access	Limited	Broad	Broad, payer-dependent
Revenue potential	Negligible	Durable generic volume	High for major brands and generics
Development rationale	Poor	Not applicable as a redevelopment asset	Stronger for differentiated products

Key Takeaways

• Phenindione is a legacy oral anticoagulant with no meaningful modern global market.
• Its commercial decline resulted from therapeutic substitution, toxicity concerns, and displacement by warfarin and DOACs.
• Original compound and historical formulation patent rights are expired or commercially irrelevant.
• Phenindione has no material current U.S. Orange Book, Paragraph IV, biosimilar, or patent-litigation profile.
• Public company filings do not identify a material current revenue stream.
• Any future product would face regulatory, safety, liability, and demand barriers rather than patent barriers.
• The only plausible opportunity is a small regional or specialty supply market, not a broad commercial relaunch.

FAQs

Is phenindione still prescribed anywhere?

Phenindione is not a standard anticoagulant in contemporary major-market clinical practice. Any remaining use would be limited and jurisdiction-specific.

Was Dindevan the same drug as phenindione?

Yes. Dindevan was a historical brand associated with phenindione, particularly in the United Kingdom.

Can a company launch a generic phenindione product?

A company could theoretically pursue approval where a regulatory pathway and reference product exist, but commercial demand and safety concerns would make the opportunity unattractive.

Does phenindione have a 180-day generic exclusivity period?

No commercially relevant current 180-day generic exclusivity position is associated with phenindione in the United States.

Is phenindione safer than warfarin?

Phenindione is not regarded as the preferred alternative to warfarin. Historical safety concerns, including blood dyscrasias and hepatic toxicity, contributed to its loss of clinical use.

References

1. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.

2. National Center for Biotechnology Information. (2024). Phenindione. PubChem Compound Summary. National Library of Medicine.

3. National Center for Biotechnology Information. (2024). Anticoagulants. LiverTox: Clinical and Research Information on Drug-Induced Liver Injury. National Library of Medicine.

4. Joint Formulary Committee. (2024). British National Formulary: Anticoagulants and antiplatelet drugs. BMJ Group and Pharmaceutical Press.

5. National Institute for Health and Care Excellence. (2021). Atrial fibrillation: Diagnosis and management. NICE guideline NG196.

6. Ruff, C. T., Giugliano, R. P., Braunwald, E., Hoffman, E. B., Deenadayalu, N., Ezekowitz, M. D., Camm, A. J., Weichert, D., Lewis, B. S., Rossebø, A. B., Murphy, S. A., Mercuri, M., & Antman, E. M. (2014). Comparison of the efficacy and safety of new oral anticoagulants with warfarin in patients with atrial fibrillation: A meta-analysis of randomised trials. The Lancet, 383(9921), 955-962.