VIDARABINE - Generic Drug Details

What are the generic drug sources for vidarabine and what is the scope of patent protection?

Vidarabine is the generic ingredient in one branded drug marketed by Parkedale and is included in two NDAs. Additional information is available in the individual branded drug profile pages.

Summary for VIDARABINE

US Patents:	0
Tradenames:	1
Applicants:	1
NDAs:	2
Raw Ingredient (Bulk) Api Vendors:	81
Clinical Trials:	1
DailyMed Link:	VIDARABINE at DailyMed

Recent Clinical Trials for VIDARABINE

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

Sponsor	Phase
National Institute of Allergy and Infectious Diseases (NIAID)	Phase 3

See all VIDARABINE clinical trials

Medical Subject Heading (MeSH) Categories for VIDARABINE

Antimetabolites

Antiviral Agents

Anatomical Therapeutic Chemical (ATC) Classes for VIDARABINE

J05AB	Nucleosides and nucleotides excl. reverse transcriptase inhibitors
J05A	DIRECT ACTING ANTIVIRALS
J05	ANTIVIRALS FOR SYSTEMIC USE
J	Antiinfectives for systemic use

S01AD	Antivirals
S01A	ANTIINFECTIVES
S01	OPHTHALMOLOGICALS
S	Sensory organs

US Patents and Regulatory Information for VIDARABINE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Parkedale	VIRA-A	vidarabine	OINTMENT;OPHTHALMIC	050486-001	Approved Prior to Jan 1, 1982		DISCN	No	No
Parkedale	VIRA-A	vidarabine	INJECTABLE;INJECTION	050523-001	Approved Prior to Jan 1, 1982		DISCN	No	No

Vidarabine Market Dynamics, Financial Trajectory, Patent Exclusivity, and Generic Risk

Last updated: September 7, 2026

Vidarabine is a legacy antiviral that has effectively exited the commercial pharmaceutical market in the United States. Its historical products, including Vira-A ophthalmic ointment and injectable vidarabine, lost practical market relevance after acyclovir and later antivirals offered better oral dosing, tolerability, selectivity, and manufacturing economics. No meaningful current branded revenue, active U.S. exclusivity, or material generic-launch opportunity is publicly identifiable. Vidarabine remains relevant mainly as a historical antiviral, a reference compound, and a potential research tool.

What is vidarabine and what products contained it?

Vidarabine, also called adenine arabinoside or ara-A, is a purine nucleoside analog with antiviral activity against herpesviruses and selected DNA viruses. It interferes with viral DNA synthesis after intracellular phosphorylation to active metabolites.

Historical dosage forms included:

Product	Historical use	Commercial status
Vidarabine ophthalmic ointment, commonly 3%	Herpes simplex keratitis	Discontinued or commercially unavailable in the U.S.
Injectable vidarabine	Severe herpesvirus infections, including herpes simplex and varicella-zoster infections	Discontinued or commercially unavailable in the U.S.
Investigational or compounded forms	Research and limited historical clinical use	No material modern commercial market

Vidarabine was approved in the United States before the modern antiviral market developed. Its historical role was concentrated in severe herpesvirus disease and ophthalmic herpes infections. Later products displaced it in most indications.

The drug had important commercial limitations. Injectable treatment required hospital-based administration, while ophthalmic treatment was less convenient and less competitive than newer topical or systemic options. Vidarabine also had a narrower commercial profile than acyclovir, which became available in oral, intravenous, and topical forms.

When did vidarabine lose exclusivity?

Vidarabine lost meaningful market exclusivity decades ago. Any original composition-of-matter and product patents would have expired by the late 20th century, given the drug's pre-1980 commercial development and approval history.

Exclusivity category	Vidarabine position
Original composition patent	Expired
Original formulation patents	Expired or commercially irrelevant
FDA regulatory exclusivity	Expired
Orphan exclusivity	No current commercial significance identified
U.S. Orange Book protection	No active commercial barrier of material value identified
Data exclusivity	Expired
Patent-term extension	No material current impact

The Hatch-Waxman framework did not create a durable protection period for vidarabine. The relevant commercial issue is not remaining exclusivity but the absence of a viable market for a mature, displaced antiviral.

What is the Orange Book status of vidarabine?

Vidarabine has no material current Orange Book position supporting a branded monopoly or an economically significant generic challenge. The FDA Orange Book records approved prescription drug products and patent or exclusivity information where applicable. Vidarabine products that were discontinued are not equivalent to actively marketed reference products with a functioning generic market.

A discontinued drug can remain relevant in regulatory records without having an active commercial franchise. That distinction matters for vidarabine. Historical approval records do not indicate current sales, active patent enforcement, or a realistic abbreviated new drug application opportunity.

The likely regulatory pathways for any future U.S. product would depend on the dosage form:

• A new ophthalmic product could require an abbreviated or full application depending on the reference-product and formulation status.
• A new injectable product would face clinical, manufacturing, and supply-chain requirements that exceed ordinary low-cost generic commercialization.
• A compounded preparation would not create a conventional branded pharmaceutical market.
• A reformulated or repurposed product could require new clinical evidence if the sponsor pursued a materially different indication or delivery system.

What patents protect vidarabine today?

No active, commercially meaningful U.S. patent estate is apparent for the original vidarabine molecule or its historical products. The key patent categories are summarized below.

Patent category	Historical relevance	Current commercial risk
Vidarabine compound patents	Protected early development and commercialization	Expired
Ophthalmic ointment patents	Covered formulation and delivery characteristics	Expired
Injectable formulation patents	Covered historical parenteral products	Expired
Manufacturing-process patents	Potentially addressed synthesis or purification	Expired or nonexclusive
Method-of-use patents	Covered antiviral treatment concepts	Expired
Modern delivery patents	Could protect a new reformulation	No established commercial estate identified

The absence of a current patent estate does not eliminate regulatory or manufacturing barriers. It means that any future sponsor would generally compete on formulation, clinical evidence, supply reliability, price, or a newly patented delivery system rather than rely on legacy molecule protection.

Are formulation patents still relevant?

Historical formulation patents for vidarabine are unlikely to block development. A sponsor could still seek new patents for:

• Improved ophthalmic retention.
• Sustained-release ocular delivery.
• Reduced local irritation.
• Stabilized injectable preparations.
• Combination therapy.
• Nanoparticle or depot formulations.
• New routes of administration.
• A targeted antiviral delivery system.

Those patents would protect the new formulation, not the underlying vidarabine molecule. Their value would depend on whether clinical performance improved enough to support reimbursement and physician adoption.

Are method-of-use patents still enforceable?

Historical method-of-use claims for treating herpes simplex, varicella-zoster, or related infections would be expected to have expired. A new use could receive patent protection only if it met novelty, nonobviousness, and written-description requirements. A simple return to an established antiviral indication would face substantial patentability challenges.

What was vidarabine's commercial trajectory?

Vidarabine followed a classic early-antiviral lifecycle: initial clinical importance, rapid displacement by a more convenient and selective competitor, then commercial withdrawal.

Early commercial period

Vidarabine entered clinical use when treatment options for serious herpesvirus infections were limited. It was valuable for severe disease and herpes keratitis, particularly before acyclovir became broadly available.

Its commercial model depended on specialist prescribing, hospital use, and ophthalmic treatment. That restricted the addressable market compared with oral antivirals.

Displacement by acyclovir

Acyclovir changed the competitive position of vidarabine. Acyclovir offered:

• Oral dosing for common herpesvirus infections.
• Intravenous dosing for severe disease.
• Better viral selectivity.
• A more familiar dosing profile.
• Stronger commercial development support.
• Broader use in recurrent and suppressive therapy.

Clinical reviews from the period generally describe acyclovir as more convenient and better tolerated than vidarabine for many herpesvirus applications. This reduced vidarabine's role in both hospital and outpatient treatment (Gnann, 2002).

Late-market decline

After acyclovir and related drugs became standard therapy, vidarabine's remaining use was limited. The product lacked a differentiated commercial position, and the market no longer supported extensive promotional activity or broad manufacturing investment.

No reliable public revenue series for vidarabine has been reported in major company filings or standard commercial databases. Parke-Davis historically marketed Vira-A, but vidarabine revenue was not separately disclosed in a way that supports a current valuation model. The appropriate financial conclusion is that vidarabine has no measurable standalone commercial franchise today.

What is the current financial trajectory for vidarabine?

Vidarabine has a near-zero direct revenue trajectory in the conventional pharmaceutical market.

Financial metric	Current assessment
Branded U.S. revenue	No material current revenue identified
Global branded revenue	No material current revenue identified
Generic revenue	No significant active market identified
Royalty stream	No current material stream identified
Licensing value	Limited unless linked to a new delivery or repurposing program
Manufacturing value	Low at commercial scale
Research value	Possible, but niche and noncommercial in most cases
Near-term growth outlook	Flat to negative without a new clinical or formulation strategy

Vidarabine should not be valued as a dormant branded asset with automatic reactivation potential. A reentry program would require a new commercial thesis, such as a resistant-virus indication, a differentiated ocular formulation, or a specialized use in a population underserved by current nucleoside analogs.

Which companies are challenging vidarabine?

No significant current Paragraph IV challenger landscape is associated with vidarabine. The drug's commercial problem is not an active generic attack. It is market abandonment and therapeutic substitution.

Historically, the competitive set included:

• Acyclovir and its generic versions.
• Valacyclovir, the oral prodrug of acyclovir.
• Ganciclovir and valganciclovir for cytomegalovirus-related indications.
• Foscarnet for selected resistant infections.
• Trifluridine for ophthalmic herpes treatment.
• Later topical agents and supportive ophthalmic therapies.

These products competed with vidarabine through clinical utility rather than patent litigation. Their advantages in dosing, route of administration, tolerability, or indication breadth weakened vidarabine's economic position.

What generic entry risks exist for vidarabine?

Generic entry risk is low in the conventional sense because there is little established branded revenue to erode. A hypothetical generic sponsor would face a different problem: proving that a small or nonexistent market can support product development and distribution.

Potential barriers include:

1. Lack of an actively marketed reference product.
2. Difficulty establishing a commercially attractive indication.
3. Limited physician demand.
4. Hospital procurement resistance to obsolete therapy.
5. Small manufacturing volumes.
6. Uncertain active pharmaceutical ingredient supply.
7. Potential need for clinical bridging or reformulation work.
8. Competition from inexpensive generic acyclovir and other antivirals.

The most plausible future entrant would not be a standard generic. It would be a specialty sponsor with a new formulation, an institutional-use strategy, or an orphan or resistant-infection development program.

What is the FDA regulatory status of vidarabine?

Vidarabine's historical FDA approvals do not translate into current commercial availability. Products can remain documented in FDA databases while being discontinued from active distribution. The FDA's discontinued-drug records and Drugs@FDA materials are important for distinguishing historical approval from current market status.

There is no evident modern FDA exclusivity period supporting vidarabine. Any new sponsor would need to determine whether an existing reference product and pathway remain usable for the proposed dosage form. A new product with materially different clinical claims could require a full development program.

FDA regulatory risk is therefore more important than patent risk. The central questions would be product quality, clinical relevance, dosage-form equivalence, and evidence of present medical need.

How strong is the vidarabine patent estate compared with modern antivirals?

Vidarabine's estate is weak because it is old, expired, and commercially unmaintained. Modern antiviral franchises typically combine composition patents, prodrug patents, formulation patents, method-of-use claims, regulatory exclusivity, and manufacturing know-how. Vidarabine has none of those protections in a meaningful current commercial configuration.

Attribute	Vidarabine	Modern antiviral franchise
Core composition protection	Expired	Often active during launch period
Formulation protection	Historical and expired	Frequently layered
Regulatory exclusivity	Expired	May be active
Clinical differentiation	Limited	Usually central to product strategy
Generic exposure	Technically high	Managed through patent layering
Manufacturing complexity	Moderate to low	Varies by molecule and dosage form
Commercial support	Minimal	Active development and promotion

What licensing or acquisition opportunities exist?

Vidarabine has limited standalone licensing value. A transaction would be more rational if it included:

• A proprietary ophthalmic delivery platform.
• A validated use against resistant herpesviruses.
• A combination regimen with clinical differentiation.
• Existing manufacturing capacity and regulatory documentation.
• Rights to a new formulation patent family.
• A non-U.S. market with limited access to newer antivirals.

Historical rights associated with Parke-Davis or successor companies would not, by themselves, establish a valuable current asset. The economic value would come from new intellectual property, new clinical data, or a defined unmet need.

What generic launch scenarios are realistic?

Three scenarios are plausible:

Scenario	Probability profile	Commercial outcome
Conventional generic reintroduction	Low	Limited demand and weak margins
New ophthalmic formulation	Low to moderate	Niche opportunity if efficacy or convenience improves
Specialty antiviral redevelopment	Low	Potential value only with new evidence and a defined resistant-virus market

A conventional low-price launch would likely struggle against generic acyclovir and established ophthalmic alternatives. A differentiated formulation could command higher pricing, but it would require new patent protection and clinical investment.

What geographic markets remain relevant?

Vidarabine has no clear large, developed-market opportunity. Any residual demand would likely be geographically fragmented and linked to local formularies, historical medical practice, or limited access to newer antivirals.

A sponsor would need to evaluate:

• Availability of acyclovir and valacyclovir.
• Local treatment guidelines.
• Hospital procurement practices.
• Regulatory recognition of legacy products.
• Active pharmaceutical ingredient supply.
• Local patent status.
• Pharmacovigilance obligations.

Global commercialization would be difficult because the competitive standard is inexpensive and widely available.

Key Takeaways

• Vidarabine is a legacy antiviral with no material current U.S. commercial franchise.
• Its original patents, formulation rights, and regulatory exclusivity have expired.
• The FDA record reflects historical approval, not an active branded market.
• Acyclovir and related antivirals displaced vidarabine through better dosing, selectivity, tolerability, and market support.
• No significant Paragraph IV or biosimilar-style challenge landscape exists.
• Current financial value is negligible unless a sponsor develops a new formulation, indication, or delivery platform.
• The principal barriers are market demand, clinical relevance, manufacturing economics, and regulatory redevelopment, not legacy patent enforcement.
• Vidarabine is more relevant as a historical compound or redevelopment candidate than as an investable commercial product.

FAQs

Is vidarabine still available by prescription?

Vidarabine is not generally available as a routinely marketed U.S. prescription antiviral. Historical ophthalmic and injectable products have been discontinued or are not commercially active.

Is vidarabine stronger than acyclovir?

No broad modern clinical advantage supports vidarabine over acyclovir. Acyclovir became the preferred therapy because of improved selectivity, oral availability, tolerability, and clinical utility.

Can a company still patent vidarabine?

A company cannot obtain a new patent simply on the old vidarabine molecule. It may pursue patents for a genuinely new formulation, delivery system, combination, or treatment method that satisfies patentability requirements.

Does vidarabine have biosimilar competition?

No. Vidarabine is a small-molecule antiviral, not a biologic. The relevant competitive category is generic small-molecule products, although no meaningful current generic market is apparent.

Could vidarabine return to the market?

A return is technically possible but commercially unlikely without a differentiated formulation, a new indication, or evidence of activity against a clinically important resistant-virus population.

References

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

2. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs. U.S. Department of Health and Human Services.

3. Gnann, J. W. (2002). Antiviral therapy of varicella-zoster virus infections. The New England Journal of Medicine, 347(5), 340-346.

4. Kimberlin, D. W., & Whitley, R. J. (2007). Antiviral therapy of HSV-1 and -2. In D. D. Richman, R. J. Whitley, & F. G. Hayden (Eds.), Clinical virology (2nd ed.). ASM Press.

5. National Library of Medicine. (n.d.). DailyMed: Vidarabine drug labeling and historical product information. U.S. National Library of Medicine.