United States Drug Patent 4,911,932: Claim Scope, Expiration, and Patent Landscape

U.S. Patent No. 4,911,932 protects a topical skin-care composition combining miconazole nitrate and zinc oxide in a claimed ratio of approximately 1:60 to 1:333, together with a diaper-rash treatment method using that composition. The patent issued on March 27, 1990, and its ordinary 17-year patent term expired on March 27, 2007. The claims no longer create an enforceable U.S. patent barrier to generic, OTC, or compounded products that use the same combination.

The patent remains relevant as a historical formulation patent and as a reference point for freedom-to-operate analysis involving miconazole nitrate, zinc oxide, diaper-rash products, and topical antifungal compositions.

What does U.S. Patent 4,911,932 cover?

U.S. Patent 4,911,932 covers two related subject matter categories:

A skin-care composition containing miconazole nitrate and zinc oxide.
A method of treating diaper rash by applying a composition containing those ingredients.

The operative limitation is the ratio between miconazole nitrate and zinc oxide. The independent claims require a ratio ranging from approximately 1:60 to 1:333.

Claim	Category	Core limitation	Scope
1	Composition	Miconazole nitrate plus zinc oxide in a ratio of about 1:60 to about 1:333	Independent composition claim
2	Composition	Claim 1 composition at about a 1:60 ratio	Narrow dependent claim
3	Method	Applying the composition to affected skin to treat diaper rash	Independent method claim
4	Method	Claim 3 method at about a 1:60 ratio	Narrow dependent method claim

The patent claims use “comprising,” which is an open-ended transitional term under conventional U.S. claim construction. A product containing the claimed miconazole nitrate and zinc oxide ratio could therefore contain additional ingredients, including carriers, emollients, preservatives, surfactants, fragrances, suspending agents, or other skin-protective materials, without automatically falling outside the claim.

What are the composition claims in U.S. Patent 4,911,932?

Claim 1 is the principal composition claim. It requires:

A skin-care composition;
Miconazole nitrate as active component (a);
Zinc oxide as active component (b); and
A miconazole nitrate-to-zinc oxide ratio from about 1:60 to about 1:333.

Claim 2 narrows claim 1 to an approximately 1:60 ratio.

The claims do not expressly require a particular:

Cream;
Ointment;
Paste;
Lotion;
Powder;
Gel;
Aerosol;
Concentration;
Container;
Preservative system;
Fragrance;
Nonionic or anionic emulsifier; or
Manufacturing process.

Unless narrower limitations appear elsewhere in the patent specification or prosecution history, the composition claims are directed principally to the ingredient combination and quantitative relationship.

How should the claimed ratio be interpreted?

The ratio is the main quantitative limitation. On the claim language provided, the relevant relationship is:

miconazole nitrate : zinc oxide = approximately 1:60 to approximately 1:333.

Examples include:

Miconazole nitrate	Zinc oxide	Approximate ratio
1 part	60 parts	1:60
1 part	100 parts	1:100
1 part	200 parts	1:200
1 part	333 parts	1:333

A formulation with a ratio below 1:60, such as 1:20, would fall outside the literal numerical range. A formulation with a ratio above 1:333, such as 1:400, would also fall outside the stated range.

The claims supplied do not state whether the ratio is calculated by weight, volume, molar quantity, or another measurement. Pharmaceutical formulation patents ordinarily use weight-based ratios when referring to quantities of solid active ingredients, but the patent specification and prosecution history would control that construction. For commercial freedom-to-operate work, the product formula, certificates of analysis, and claim-construction record would need to be evaluated against the patent’s defined measurement basis.

What are the diaper-rash method claims?

Claim 3 covers a method for treating diaper rash by applying to affected skin a composition containing:

An antimicrobially effective amount of miconazole nitrate;
Zinc oxide; and
The same approximately 1:60-to-1:333 ratio required by claim 1.

Claim 4 narrows the method to an approximately 1:60 ratio.

The method claims add a use limitation that does not appear in the composition claims. The composition must be applied to affected skin, and the purpose must be treatment of diaper rash. A product could therefore be evaluated differently under the composition and method claims:

A product sold for general skin care could potentially implicate claim 1 if it satisfies the composition limitations.
A product used specifically to treat diaper rash could implicate claim 3 if it satisfies both the ingredient-ratio and use limitations.
A composition outside the claimed ratio would not literally satisfy either claim 1 or claim 3.

The phrase “antimicrobially effective amount” imposes a functional limitation in claim 3. It requires an amount capable of producing the claimed antimicrobial treatment result under the relevant conditions. The claim does not state a fixed miconazole nitrate concentration.

When did U.S. Patent 4,911,932 expire?

U.S. Patent 4,911,932 issued on March 27, 1990. Patents filed before the transition to the 20-year term generally received a 17-year term measured from grant under the former U.S. patent-term regime. On that basis, the patent expired on March 27, 2007, absent an unusual term adjustment, terminal disclaimer, or other record-specific event. The patent is therefore expired and cannot presently block commercial practice of the claimed combination in the United States. [1, 2]

Event	Date or status
Patent number	U.S. 4,911,932
Issue date	March 27, 1990
Ordinary term	17 years from issue
Estimated ordinary expiration	March 27, 2007
Current enforceability	Expired
Current Paragraph IV relevance	None for this patent
Current injunction risk based solely on this patent	None

Patent expiration does not eliminate other possible rights, such as later patents covering a particular formulation, packaging system, manufacturing process, dosage form, or commercial product. It does eliminate the enforceable exclusionary rights created by Patent 4,911,932 itself.

What is the Orange Book status of U.S. Patent 4,911,932?

U.S. Patent 4,911,932 is not expected to function as a current Orange Book barrier.

The FDA Orange Book principally lists patents and exclusivity information submitted for approved prescription drug products under the Hatch-Waxman framework. Miconazole nitrate and zinc oxide topical products are generally associated with OTC monograph regulation rather than a conventional prescription NDA product protected by an active Orange Book patent listing. FDA’s OTC framework separately addresses topical antifungal and skin-protectant ingredients, including miconazole nitrate and zinc oxide. [3-5]

The practical consequences are:

The patent’s expiration removes any remaining Hatch-Waxman patent block.
An ANDA applicant would not face a current Paragraph IV challenge directed to this expired patent.
An OTC manufacturer would generally evaluate monograph compliance, labeling, manufacturing controls, and any later patents rather than rely on this patent for market exclusivity.
The patent does not confer current regulatory exclusivity.

Does U.S. Patent 4,911,932 create generic entry risk today?

The patent itself creates no current generic-entry risk because it expired in 2007.

A manufacturer can generally develop a miconazole nitrate and zinc oxide product corresponding to the claimed combination without infringing an expired U.S. patent. The principal present-day barriers are regulatory and commercial rather than patent-based:

Compliance with the applicable FDA OTC monograph or approved application pathway;
Product quality and stability;
Uniformity of zinc oxide and miconazole nitrate distribution;
Microbial control;
Labeling and permissible therapeutic claims;
Manufacturing scale-up;
Consumer acceptance;
Retail distribution; and
Any later, unexpired patents covering a specific product or formulation.

The patent’s historical claims could still matter in due diligence because they identify the claimed technical concept and may have influenced later formulation work. They do not support an injunction, damages claim, or compulsory license against a current U.S. manufacturer.

What formulations are protected by the patent?

The patent claims potentially cover topical compositions containing the two specified active ingredients in the claimed ratio, regardless of whether the formulation is presented as a cream, ointment, paste, lotion, or another topical vehicle, subject to the full claim language and specification.

The claims do not expressly require a particular zinc oxide percentage. Instead, the zinc oxide amount is controlled relative to miconazole nitrate. For example:

1% miconazole nitrate with 60% zinc oxide corresponds to 1:60.
1% miconazole nitrate with 100% zinc oxide corresponds to 1:100.
0.3% miconazole nitrate with 20% zinc oxide corresponds to approximately 1:66.7.
2% miconazole nitrate with 12% zinc oxide corresponds to 1:6 and falls outside the stated range.

The ratio limitation distinguishes this patent from ordinary miconazole antifungal products and ordinary zinc oxide barrier products. A formulation containing only one of the ingredients would not satisfy the combination requirement.

Are formulation patents still relevant after expiration?

They are relevant for historical product-line analysis, not as current exclusionary rights. An expired formulation patent can help identify:

Earlier product concepts;
Prior-art disclosures;
Potential continuation or divisional activity;
Technical development paths;
Formulation design-around strategies; and
The distinction between ingredient patents and later delivery-system patents.

A current product review should search later U.S. patents that claim specific emulsions, particle sizes, encapsulation systems, barrier compositions, preservative combinations, or branded product formulations. Those later rights are legally separate from Patent 4,911,932.

Are there method-of-use patents covering diaper-rash treatment?

Patent 4,911,932 includes method-of-use claims directed specifically to treating diaper rash. Claims 3 and 4 require application to affected skin and use of the miconazole nitrate-zinc oxide combination within the stated ratio.

Those claims expired with the patent. They do not currently prevent:

Labeling a product for diaper-rash treatment;
Applying the combination to diaper-rash-affected skin;
Conducting clinical or consumer testing;
Selling an otherwise lawful OTC product; or
Using a different ratio or formulation.

Current labeling must still comply with FDA requirements. The expired method claims have no continuing regulatory effect.

Which companies are challenging U.S. Patent 4,911,932?

No current Paragraph IV challenge is commercially relevant because the patent expired more than 18 years ago. Paragraph IV certifications address listed patents that remain relevant to an ANDA product. An expired patent does not provide a present patent term that can delay FDA approval or trigger the ordinary Hatch-Waxman litigation timetable. [6]

The patent may have been owned or commercialized by an entity associated with the original miconazole product franchise, but ownership history does not change the current legal position. A patent assignment, license, or settlement agreement cannot revive an expired patent term.

Did the patent involve licensing deals or settlement agreements?

An expired patent can no longer support a forward-looking exclusive license in the ordinary patent-rights sense. Historical licenses, supply agreements, or settlements may have existed, but they would require separate assignment, litigation, or contract records. The claim text and basic patent record do not establish a current licensing restriction or settlement-based market block.

Any historical agreement would need to be distinguished from:

Patent ownership;
Regulatory exclusivity;
Trademark rights;
Trade-secret manufacturing rights;
Distribution agreements; and
Product-specific commercial contracts.

The patent’s expiration ends the patent exclusion period but does not terminate unrelated contractual obligations.

How strong is the patent estate for miconazole nitrate and zinc oxide?

The estate represented by Patent 4,911,932 is legally weak today because the patent is expired. During its term, the patent had meaningful claim coverage because it combined composition claims with diaper-rash method claims.

Estate characteristic	Assessment
Composition coverage	Directly targeted miconazole nitrate plus zinc oxide
Numerical limitation	Significant; ratio range limits claim breadth
Dosage-form limitation	Broad on the supplied claim language
Method-of-use coverage	Diaper-rash treatment
Manufacturing coverage	None apparent in the supplied claims
Biosimilar relevance	None
Current patent life	None
Current blocking value	None
Historical design-around options	Change ratio, omit one active, or use a different composition

The estate was narrower than a broad miconazole composition patent because it required zinc oxide and a defined ratio. It was broader than a highly specific cream claim because it did not, on the supplied language, require a named vehicle or detailed excipient system.

Does biosimilar risk apply to this patent?

No. Biosimilar regulation applies to biological products, not to conventional small-molecule miconazole nitrate and inorganic zinc oxide topical products. The relevant competitive pathway is generic or OTC competition, not a 351(k) biosimilar pathway under the Public Health Service Act. [7]

Potential competitors include:

OTC antifungal manufacturers;
Zinc oxide diaper-rash product manufacturers;
Private-label retailers;
Compounding pharmacies;
Contract manufacturers; and
Branded topical-care companies.

The main competitive distinction is likely to be formulation performance, labeling, retail placement, and consumer trust rather than patent exclusivity.

What manufacturing and IP barriers remain?

Patent 4,911,932 does not claim a manufacturing process in the provided claims. Manufacturing barriers therefore arise from execution rather than from this patent.

Important technical issues include:

Uniform dispersion of miconazole nitrate and zinc oxide;
Particle-size control;
Prevention of agglomeration;
Stability in the selected vehicle;
Preservation and microbial limits;
Skin tolerability;
Compatibility with packaging;
Batch-to-batch assay control; and
Demonstration that the finished product meets labeled strength.

A manufacturer should also screen later patents covering high-zinc-oxide barrier systems, antifungal combinations, delivery vehicles, encapsulation, aerosol systems, and specialized pediatric skin-care formulations. These later rights could create more relevant freedom-to-operate issues than Patent 4,911,932.

How does this patent compare with ordinary miconazole and zinc oxide products?

Product type	Miconazole nitrate	Zinc oxide	Relationship to Patent 4,911,932
Miconazole antifungal alone	Present	Absent	Does not meet combination limitation
Zinc oxide barrier cream alone	Absent	Present	Does not meet combination limitation
Combination product, ratio 1:60 to 1:333	Present	Present	Historically within claim scope
Combination product, ratio below 1:60	Present	Present	Outside literal ratio range
Combination product, ratio above 1:333	Present	Present	Outside literal ratio range
Combination with additional actives	Present	Present	Potentially covered because “comprising” is open-ended, subject to ratio

The patent was directed to a specific combination strategy: antifungal activity from miconazole nitrate and barrier or protective activity from zinc oxide. It did not claim either ingredient in isolation.

Key Takeaways

U.S. Patent 4,911,932 claims miconazole nitrate and zinc oxide compositions at an approximately 1:60-to-1:333 ratio.
Claims 1 and 2 cover compositions; claims 3 and 4 cover diaper-rash treatment methods.
The claims do not expressly limit the formulation to a particular cream, ointment, paste, vehicle, or excipient system.
The patent issued on March 27, 1990, and its ordinary 17-year term expired on March 27, 2007.
The patent creates no current U.S. patent barrier to generic or OTC products.
Paragraph IV litigation and biosimilar pathways are not currently relevant to this expired small-molecule topical patent.
Current freedom-to-operate analysis should focus on later patents, FDA OTC requirements, labeling, formulation performance, manufacturing controls, and commercial rights.

FAQs

Can a company sell a miconazole nitrate and zinc oxide diaper-rash product today?

Yes, Patent 4,911,932 is expired. The product must still satisfy applicable FDA requirements and avoid infringement of any later unexpired patents.

Does a 1:60 formulation receive special protection under the patent?

Historically, claim 2 and claim 4 specifically recited an approximately 1:60 ratio. That protection expired with the patent in 2007.

Does the patent cover zinc oxide diaper-rash cream without miconazole?

No. The claims require both miconazole nitrate and zinc oxide.

Does the patent cover a miconazole product with a small amount of zinc oxide?

Only if the miconazole nitrate-to-zinc oxide ratio falls within the claimed range. A formulation with a materially lower zinc oxide amount may fall outside the literal claims.

Can a later patent restore exclusivity under U.S. Patent 4,911,932?

No. The expired patent cannot be revived. A later patent could protect a new formulation, manufacturing process, delivery system, or use only if it satisfies separate patentability and infringement requirements.

References

United States Patent and Trademark Office. (1990). U.S. Patent No. 4,911,932.
United States Code, 35 U.S.C. § 154(c). Patent term provisions for pre-1995 applications.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations (Orange Book).
21 C.F.R. § 333.210. Topical antifungal drug products.
21 C.F.R. § 347.10. Skin protectant active ingredients.
United States Code, 21 U.S.C. § 355(j). Abbreviated new drug applications and patent certifications.
United States Code, 42 U.S.C. § 262(k). Biosimilar biological product licensure.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	42039	⤷ Start Trial
Australia	3775885	⤷ Start Trial
Australia	569602	⤷ Start Trial
Canada	1250522	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,911,932

Summary for Patent: 4,911,932