Last updated: September 8, 2026
Griseofulvin microsize is a mature, low-cost generic antifungal with limited commercial growth potential. Its patent and regulatory exclusivity have expired, no biosimilar pathway applies, and the product has no meaningful branded-market protection in the United States. Demand persists in selected dermatophyte infections, especially tinea capitis, but oral terbinafine and azole antifungals constrain expansion. The commercial opportunity is concentrated in manufacturing efficiency, reliable supply, pediatric liquid formulations, veterinary demand, and geographic markets where newer antifungals remain less accessible.
What is griseofulvin microsize and how is it used?
Griseofulvin microsize is an oral antifungal derived from Penicillium species. It inhibits fungal mitosis and concentrates in keratinized tissues, including skin, hair, and nails. The microsize formulation has lower particle size than conventional griseofulvin and is absorbed better when taken with a fatty meal.
The product is used for dermatophyte infections, including:
- Tinea capitis
- Tinea corporis
- Tinea pedis
- Tinea cruris
- Tinea barbae
- Tinea unguium and other dermatophyte nail infections
The FDA labeling states that griseofulvin is indicated for infections caused by susceptible species of Microsporum, Epidermophyton, and Trichophyton. It is not effective against bacterial, candidal, or systemic fungal infections.[1]
Common dosage forms include:
| Dosage form |
Typical strength |
Commercial relevance |
| Microsize tablet |
500 mg |
Low-cost oral solid; principal generic format |
| Microsize oral suspension |
125 mg/5 mL |
Important for pediatric tinea capitis |
| Ultramicrosize tablet |
125 mg and 250 mg |
Separate formulation with lower required dose |
| Oral suspension products |
Product-specific |
Supply and availability vary by manufacturer |
Griseofulvin microsize and griseofulvin ultramicrosize are not interchangeable on a milligram-for-milligram basis. The ultramicrosize formulation has higher bioavailability and generally requires a lower dose.[1]
What is the FDA regulatory status of griseofulvin microsize?
Griseofulvin microsize is an FDA-approved prescription drug marketed primarily through abbreviated new drug applications and legacy approved products. The product is an old small-molecule medicine with no current new-drug exclusivity.
FDA approval and generic pathway
Generic griseofulvin microsize products are approved under the Abbreviated New Drug Application pathway. Applicants must demonstrate pharmaceutical equivalence and bioequivalence to the applicable reference product. The regulatory burden is materially lower than for a new chemical entity because clinical efficacy has already been established.
FDA requirements generally focus on:
- Active ingredient identity and strength
- Dosage-form equivalence
- Dissolution and bioequivalence
- Manufacturing controls
- Stability
- Labeling consistency
- Container and closure performance
The product does not require a biosimilar application. Griseofulvin is a chemically defined small molecule, so abbreviated generic applications, rather than Biologics License Applications or biosimilar applications, govern market entry.
FDA exclusivity
No meaningful period of FDA new-drug, orphan-drug, pediatric, or qualified-infectious-disease exclusivity protects ordinary griseofulvin microsize products today. The drug’s commercial protection is therefore based on manufacturing, distribution, sourcing, and market access rather than regulatory exclusivity.
What patents protect griseofulvin microsize?
No commercially significant active U.S. patent estate protects the griseofulvin microsize active ingredient or its standard generic tablet and suspension forms.
| Protection category |
Current commercial position |
| Composition-of-matter patent |
Expired |
| Basic formulation patents |
Expired or no longer commercially relevant |
| Standard microsize tablet patents |
No active protection identified as a market barrier |
| Pediatric suspension patents |
No material active protection identified |
| Method-of-use patents |
No material current barrier to generic treatment of dermatophyte infections |
| Manufacturing patents |
Potentially relevant at the process level, but not a broad barrier to generic competition |
| FDA exclusivity |
None of practical commercial significance |
| Biosimilar exclusivity |
Not applicable |
Historical griseofulvin patents date from the early development period of the drug and do not support modern exclusivity. Patent protection for early antifungal compounds generally expired decades ago. The FDA Orange Book remains the principal source for checking patents and exclusivity associated with approved listed drugs, but mature griseofulvin products do not present the type of active patent listing seen with recently approved specialty drugs.[2]
Are formulation patents a commercial risk?
Formulation patents are unlikely to create a broad market barrier for standard griseofulvin microsize. A manufacturer could still seek protection for a narrowly defined formulation, such as:
- A modified-release tablet
- A taste-masked pediatric suspension
- A high-stability liquid
- A novel excipient system
- A fixed-dose combination
- A specialized topical or transdermal delivery system
Such patents would protect only the claimed formulation and would not prevent competition from conventional microsize tablets or suspensions. The commercial value of a new formulation would depend on demonstrated improvement in adherence, absorption, tolerability, storage, or dosing convenience.
When does griseofulvin microsize lose exclusivity?
Griseofulvin microsize lost meaningful market exclusivity long before the modern generic-drug era. Its active ingredient, conventional oral formulations, and principal therapeutic uses have been open to generic competition for decades.
The exclusivity timeline is therefore historical rather than prospective:
| Milestone |
Commercial implication |
| Original clinical development |
Established systemic treatment for dermatophyte infections |
| Original compound and formulation patents |
Expired |
| Legacy branded products |
Replaced or supplemented by generic products |
| ANDA approvals |
Expanded multi-source competition |
| Current market |
Low-price generic and limited branded participation |
| Future exclusivity event |
None apparent for conventional microsize products |
A generic entrant does not face a conventional patent cliff. It enters an already commoditized market.
How many patents cover griseofulvin microsize?
No active U.S. patent portfolio appears to provide meaningful exclusivity for conventional griseofulvin microsize tablets or suspensions. The relevant commercial count is effectively zero for broad composition, standard dosage form, and established method-of-use protection.
This does not mean that no patent anywhere references griseofulvin. Patent documents may mention the drug in combination products, pharmaceutical compositions, manufacturing processes, or research applications. Those documents do not necessarily create an enforceable barrier against a conventional generic microsize product.
Geographic coverage is also limited in practical value. Any surviving foreign patent would need to cover a commercially relevant product and remain enforceable in a market with sufficient demand. For griseofulvin, the principal market constraint is demand and price, not patent scope.
Which companies manufacture or market griseofulvin microsize?
The U.S. market has historically included generic manufacturers and marketers such as:
- Amneal Pharmaceuticals
- Rising Pharma Holdings
- Northwind Pharmaceuticals
- Upsher-Smith Laboratories
- Pharmaceutical companies operating through contract manufacturing or private-label arrangements
Product availability changes as companies discontinue low-volume products, transfer marketing rights, or alter supply arrangements. The market has also included branded or legacy products associated with Gris-PEG and other griseofulvin labels, but Gris-PEG is an ultramicrosize product rather than a microsize equivalent.
Because generic manufacturers generally do not report griseofulvin revenue separately, market-share analysis is more reliable through FDA listing data, National Drug Code records, wholesaler availability, prescription claims, and tender data than through public company filings.[3]
What is the market size and financial trajectory for griseofulvin microsize?
Griseofulvin microsize is a mature, low-revenue product at the manufacturer level. The market has a long-term declining or flat trajectory in developed countries, with periodic supply-driven volatility.
Revenue drivers
The main revenue drivers are:
- Prescription volume for tinea capitis and other dermatophyte infections.
- Pediatric use, particularly oral liquid demand.
- Availability of low-cost alternatives.
- Generic manufacturer participation.
- Hospital, clinic, and public-sector procurement.
- Veterinary and international demand.
- Temporary shortages affecting price and substitution.
The market does not benefit from premium specialty-drug pricing. Generic pricing is constrained by therapeutic substitution, multiple suppliers, pharmacy purchasing power, and limited prescriber loyalty.
Why revenue has declined
Oral terbinafine has replaced griseofulvin in many dermatophyte indications, particularly certain Trichophyton infections. Terbinafine has a shorter treatment course in several settings and is often preferred for adult skin and nail infections. Azoles, including itraconazole and fluconazole, provide additional alternatives.
Griseofulvin remains relevant when:
- Tinea capitis is caused by Microsporum
- Pediatric experience and safety familiarity influence prescribing
- Terbinafine susceptibility is less favorable
- A clinician prefers established therapy
- Cost or availability limits access to alternatives
- Veterinary treatment protocols call for griseofulvin
Financial profile
Public company reports generally do not disclose griseofulvin microsize revenue as a separate line item. The product is typically included within broader generic pharmaceutical revenue. Its financial profile has the following characteristics:
| Metric |
Assessment |
| Revenue growth |
Low or negative over the long term |
| Gross margin |
Sensitive to manufacturing scale and competition |
| Pricing power |
Minimal |
| Regulatory risk |
Low for established products |
| Supply-chain risk |
Moderate because low-volume products may have few suppliers |
| R&D upside |
Low without a differentiated formulation |
| Licensing value |
Low for the conventional product |
| Cash-flow profile |
Stable only where manufacturing and distribution costs are tightly controlled |
A manufacturer can earn acceptable returns if it has an efficient supply chain, a dependable active pharmaceutical ingredient source, and limited direct competition. The product is unlikely to support large commercial investment without a formulation, geographic, or channel-specific strategy.
What generic entry risks exist for griseofulvin microsize?
Generic entry risk is high because the product has no meaningful patent barrier. The commercial risk is asymmetric: entry is technically feasible, but the entrant may face insufficient volume to justify launch costs.
Risks to incumbent manufacturers
- Price erosion from additional ANDA holders
- Pharmacy substitution
- Product discontinuation by large suppliers
- Loss of shelf position to lower-cost competitors
- Contract-manufacturing disruptions
- Active pharmaceutical ingredient shortages
- Low-volume production inefficiency
- Liability associated with pediatric dosing or labeling errors
Risks to new entrants
- Limited prescription volume
- Low reimbursement and purchasing prices
- Established wholesaler relationships
- Difficulty achieving manufacturing scale
- Need to maintain oral-liquid supply
- Inventory write-offs if demand shifts to terbinafine or azoles
- Product shortage penalties or customer loss after supply interruptions
The most realistic generic launch scenario is a low-cost, targeted launch through a specialty generic, institutional, pediatric, or international channel. A broad U.S. launch aimed at rapid market share would have limited upside.
Are there Paragraph IV challenges involving griseofulvin microsize?
Paragraph IV litigation is not a material current feature of the conventional griseofulvin microsize market. Paragraph IV certifications are used when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or not infringed. Because standard griseofulvin microsize products do not have commercially important active patent protection, there is little incentive for a conventional Paragraph IV campaign.
A new formulation could generate Paragraph IV activity if a reference product carried an unexpired formulation or method-of-use patent. That scenario would concern the specific formulation, not the ordinary microsize active ingredient.
What patent litigation affects griseofulvin microsize?
No major current U.S. patent litigation appears to affect the conventional griseofulvin microsize market. The product is not associated with the type of ongoing litigation seen in high-value oncology, immunology, diabetes, or rare-disease products.
There is also no material settlement structure shaping generic entry. A settlement would be commercially meaningful only if an active patent created a delayed-entry date or other market restriction. That condition does not characterize standard griseofulvin microsize.
What licensing deals involve griseofulvin microsize?
There is no major current licensing transaction that defines the conventional griseofulvin microsize market. Historical rights transfers may have occurred as branded products moved among pharmaceutical companies, but these transactions do not create current exclusivity.
Potential licensing value would arise from:
- A pediatric liquid with improved palatability
- A novel delivery system
- A combination product
- A regional distribution agreement
- A veterinary formulation
- A manufacturing process that materially lowers cost
- A product designed for markets with limited access to terbinafine or azoles
For a standard generic tablet, licensing economics are generally weak because the active ingredient and formulation are widely available.
How does griseofulvin microsize compare with terbinafine and azole antifungals?
| Factor |
Griseofulvin microsize |
Terbinafine |
Itraconazole or fluconazole |
| Drug class |
Griseofulvin antifungal |
Allylamine |
Triazole |
| Patent status |
Long expired |
Generic competition; product-specific patent history |
Generic competition; product-specific patent history |
| Main use |
Dermatophyte infections, especially selected tinea capitis cases |
Skin, nail, and dermatophyte infections |
Broad dermatophyte and yeast use |
| Pediatric relevance |
Significant in tinea capitis |
Increasingly used depending on organism and age |
Product- and indication-dependent |
| Treatment duration |
Often longer |
Often shorter in selected indications |
Regimen varies |
| Monitoring concerns |
Drug interactions and hepatic considerations |
Hepatic risk and drug interactions |
Drug interactions and hepatic considerations |
| Pricing |
Very low generic pricing |
Low generic pricing |
Low generic pricing |
| Growth outlook |
Mature to declining |
More resilient |
Stable to indication-dependent |
Griseofulvin retains clinical value where organism-specific response, pediatric experience, or local practice supports its use. It has limited ability to regain broad market share without a meaningful clinical or delivery advantage.
What manufacturing and intellectual-property barriers remain?
Manufacturing is a more relevant barrier than intellectual property. Key operational requirements include:
- Consistent particle-size control
- Uniform content in tablets and suspensions
- Stable oral-liquid formulation
- Reliable micronization capability
- Control of dissolution and bioavailability
- Validated cleaning for potent or sensitizing materials
- Stable API sourcing
- Compliance with current good manufacturing practice requirements
Micronization can affect dissolution and absorption. A manufacturer that produces a product outside the expected particle-size or dissolution profile may face bioequivalence, stability, or inspection problems. These technical requirements do not create patent exclusivity, but they can limit the number of reliable suppliers.
The suspension is commercially more differentiated than the 500 mg tablet because pediatric products require acceptable taste, dosing accuracy, storage stability, and dependable availability.
What is the competitive outlook for griseofulvin microsize?
The competitive outlook is defensive rather than expansionary. The principal opportunities are operational:
- Maintain supply during competitor shortages
- Secure low-cost API and micronization capacity
- Protect pediatric liquid availability
- Serve institutional and international tenders
- Develop improved palatability or dosing formats
- Use contract manufacturing to avoid fixed-cost exposure
- Target veterinary or underserved regional channels
The largest threat is not patent litigation. It is substitution by terbinafine and azole products combined with generic price compression.
Key Takeaways
- Griseofulvin microsize is a mature, off-patent generic antifungal.
- No meaningful active U.S. patent estate protects the conventional microsize tablet or suspension.
- FDA exclusivity has expired, and biosimilar regulation does not apply.
- Paragraph IV litigation and patent settlements are not material current market factors.
- Revenue is generally not reported separately by public manufacturers.
- The long-term financial trajectory is flat to declining in developed markets.
- Pediatric suspension supply, low-cost manufacturing, and international access are the main commercial opportunities.
- Terbinafine and azole antifungals limit growth, although griseofulvin remains clinically relevant for selected tinea capitis cases.
- Manufacturing reliability is a greater barrier than intellectual property.
- A differentiated formulation would be required to create meaningful licensing or premium-pricing value.
FAQs
Is griseofulvin microsize still commercially available?
Yes. Availability varies by manufacturer, dosage form, pharmacy channel, and country. The 500 mg tablet and pediatric oral suspension are the most commercially relevant forms.
Does griseofulvin microsize have an Orange Book patent?
Conventional griseofulvin microsize products do not have a commercially meaningful active patent listing that blocks ordinary generic entry. The Orange Book should be checked for product-specific listings because marketing authorizations can change.
Is griseofulvin microsize interchangeable with Gris-PEG?
No. Gris-PEG is an ultramicrosize formulation. Microsize and ultramicrosize products have different bioavailability and dosing characteristics and should not be substituted on a milligram-for-milligram basis.[1]
Can a company obtain FDA exclusivity for a new griseofulvin formulation?
Potentially, but only if the product satisfies the requirements for an applicable regulatory exclusivity category. A new formulation could also rely on patent protection, but protection would attach to the specific formulation or use rather than to conventional griseofulvin microsize.
Is veterinary demand material to the griseofulvin microsize market?
Veterinary demand can support niche volume, particularly for dermatophyte infections in companion animals. It is unlikely to transform the economics of the human generic market but may improve utilization of specialized manufacturing or distribution channels.
References
-
U.S. Food and Drug Administration. (2023). Griseofulvin microsize tablets: Prescribing information. FDA labeling database.
-
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. FDA Orange Book.
-
National Library of Medicine. (2024). DailyMed: Griseofulvin microsize product labeling. U.S. National Library of Medicine.
-
Centers for Disease Control and Prevention. (2024). Clinical guidance for ringworm and tinea infections. U.S. Department of Health and Human Services.
-
U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs database. FDA.
