United States Drug Patent 5,401,741: Scope, Claims, Expiration, and Ofloxacin Otic Patent Landscape

U.S. Patent No. 5,401,741 covered methods of treating otopathy by topically administering ofloxacin or an ofloxacin salt to the affected ear. Its practical commercial scope centered on 0.3% aqueous ofloxacin ear drops administered by instillation for otitis externa and otitis media. The patent expired in 2012 and no longer creates an enforceable barrier to generic ofloxacin otic products. It was a method-of-use patent, not a current composition, active-ingredient, or manufacturing patent.

What does U.S. Patent 5,401,741 protect?

U.S. Patent 5,401,741 protects a therapeutic method requiring the following elements:

The condition treated is an otopathy.
The active agent is ofloxacin or a salt of ofloxacin.
The product is administered topically through the ear.
The active agent is present in a pharmaceutically acceptable carrier.
The administered quantity is effective to treat the condition.

The broadest claim is claim 1. It does not expressly require an aqueous formulation, a particular concentration, a particular dosage volume, or a particular delivery device.

Patent element	Scope under claim 1
Active ingredient	Ofloxacin or an ofloxacin salt
Therapeutic target	Otopathy
Route	Topical otic administration
Vehicle	Pharmaceutically acceptable carrier
Dose	Amount effective to treat
Site	Area affected by otopathy
Dosage form	Not limited by claim 1

The claim is directed to use rather than ownership of ofloxacin itself. A party could therefore practice the claimed method with a formulation that was independently known or protected by another patent.

The patent is particularly relevant to products marketed as ofloxacin otic solution, including products using approximately 0.3% ofloxacin in an aqueous vehicle.

What do the individual claims cover?

Claim 1: Broad otic treatment method

Claim 1 covers topical otic administration of ofloxacin or an ofloxacin salt for treating otopathy. The term "otopathy" is broad and can encompass diseases of the ear, subject to the patent's specification and ordinary claim-construction principles.

The claim does not limit treatment to infection. A product or use directed to an ear disorder could potentially fall within the claim if the other elements were met and the disorder qualified as an otopathy.

The main limitations are:

Ofloxacin must be the active therapeutic agent.
Administration must be topical and otic.
The carrier must be pharmaceutically acceptable.
The dose must be therapeutically effective.

A systemic oral or intravenous ofloxacin regimen would not satisfy the topical otic administration limitation.

Claim 2: Otitis media

Claim 2 narrows claim 1 to treatment of otitis media. It retains all limitations of claim 1 and adds the disease limitation.

This claim is commercially significant because otitis media can involve the middle ear, including treatment through a perforated tympanic membrane or other access route. The claim does not, on its face, require a particular type of tympanic membrane condition.

Claim 3: Apparent dependency and disease-category inconsistency

The supplied text states:

"The method of claim 2 wherein said otopathy is otitis externa."

As written, claim 3 depends on claim 2, which already specifies otitis media, while claim 3 substitutes otitis externa. That creates a logical inconsistency. A method cannot ordinarily be limited simultaneously to otitis media and otitis externa unless the claim is interpreted as covering both conditions or the dependency is corrected.

The likely commercial intent was to claim treatment of otitis externa separately. The quoted language may reflect a transcription error, a claim-formatting error, or an inaccurate reproduction of the issued claims. A legal opinion on infringement would require reliance on the certified patent document and prosecution history rather than the supplied text alone.

Claim 4: Concentration range

Claim 4 limits the concentration of ofloxacin to approximately 0.05% to approximately 2% weight/volume.

This range includes the conventional 0.3% ofloxacin otic solution:

Product concentration	Within claim 4 range?
0.05% w/v	Yes, at the lower boundary
0.1% w/v	Yes
0.2% w/v	Yes
0.3% w/v	Yes
0.5% w/v	Yes
1.0% w/v	Yes
2.0% w/v	Yes, at the upper boundary
Above 2% w/v	Not literally within the stated range

The use of "about" gives the concentration limitation some tolerance around the endpoints. The scope would depend on the specification, prosecution history, and any applicable doctrine-of-equivalents analysis.

Claim 5: Aqueous solution

Claim 5 narrows claim 4 to an aqueous solution. It excludes nonaqueous oils, suspensions, gels, ointments, and other dosage forms unless a court construed the formulation as an aqueous solution.

The claim therefore maps closely to the standard ofloxacin otic dosage form: ofloxacin dissolved in water with suitable excipients and pH adjustment.

Claim 6: Instillation into the external auditory canal

Claim 6 requires application of the aqueous solution to the external auditory canal by instillation. This limitation targets conventional ear-drop administration.

It does not require:

A specific drop volume.
A specific dosing frequency.
A particular bottle or dropper.
A particular preservative.
A specific patient age.
A tympanostomy tube.

A product administered as ear drops into the external auditory canal would fall within the practical center of this claim if the concentration and other limitations were met.

Claim 7: Intratympanic injection

Claim 7 adds intratympanic injection through a puncture in the tympanic membrane. As supplied, it depends on claim 6 and therefore appears to inherit the instillation requirement as well as the aqueous solution, concentration, otitis media, and topical administration limitations.

That creates an unusual claim structure. Intratympanic injection and external-canal instillation are distinct administration techniques. If claim 7 truly depends from claim 6, a literal reading could require both techniques. The claim may have been intended to depend from an earlier claim or to describe an alternative route.

When did U.S. Patent 5,401,741 expire?

The patent expired in 2012. FDA product information historically identified June 18, 2012, as the patent expiration date associated with the Floxin Otic product. The patent therefore no longer blocks generic entry or current use of the claimed method.

Event	Date or status
U.S. patent number	5,401,741
Issue date	March 28, 1995
Patent subject	Ofloxacin otic treatment methods
Historical reference product	Floxin Otic
Historical Orange Book relevance	Method-of-use listing
Expiration	June 18, 2012
Current enforceability	Expired
Current generic barrier	None from this patent

The expiration date is the critical commercial fact. Even if a product satisfies every limitation of an issued claim, an expired patent cannot support an infringement action for post-expiration conduct.

What was the FDA and Orange Book status of the patent?

The patent was associated with the ofloxacin otic product Floxin Otic and was historically listed in FDA product and patent information. Floxin Otic was a small-molecule drug product approved through the NDA pathway. Generic ofloxacin otic products are generally approved through abbreviated new drug applications, or ANDAs, rather than through the biosimilar pathway.

The patent did not protect the basic ofloxacin molecule. It covered a therapeutic use involving otic administration. The Orange Book distinction matters because use patents can be addressed through a section viii statement or Paragraph IV certification, depending on the listed indication, product labeling, and the scope of the patent claims.

Paragraph IV relevance

A generic applicant seeking approval before patent expiry could have taken one of several positions:

certify that the patent was invalid;
certify that the patent was not infringed;
assert that the patent was unenforceable;
submit a section viii statement carving out a patented method of use, where FDA labeling and the listed use permitted a lawful carve-out.

A Paragraph IV certification could have triggered litigation under the Hatch-Waxman statute. A timely patent-infringement action could also have produced a 30-month stay of approval under the statutory framework. Those mechanisms became immaterial after the 2012 expiration date. [3]

What formulations are protected by the patent?

The patent's formulation coverage is layered rather than absolute.

Formulation or use	Likely relationship to the claims
0.3% aqueous ofloxacin ear drops	Central commercial embodiment
0.05%-2% aqueous ofloxacin solution	Within claims 4-6 if other limitations are met
Ofloxacin suspension	Potentially within claim 4 only if not excluded by claim construction; not clearly within claim 5
Ofloxacin ointment	Potentially within claim 1, but not claims requiring aqueous solution
Ofloxacin gel	Potentially within claim 1 depending on carrier and administration
Oral ofloxacin tablet	Outside the topical otic route
Intravenous ofloxacin	Outside the topical otic route
Intratympanic aqueous solution	Addressed by claim 7 as supplied
Ciprofloxacin otic product	Outside the ofloxacin limitation

The broadest claim could reach nonaqueous carriers, provided they are pharmaceutically acceptable and used for topical otic administration. Claims 5 and 6 materially narrow that scope to aqueous ear-drop products.

The patent does not appear to claim a proprietary device, bottle, closure, preservative system, or manufacturing process. A later formulation patent could therefore have covered excipient selection, stability, preservative concentration, packaging, or a specialized delivery system without being coextensive with this patent.

How strong was the patent estate for ofloxacin otic products?

The patent estate was commercially meaningful during the period before expiration but narrow in structure.

Estate component	Assessment
Active ingredient patent	Separate historical protection; not the subject patent
Otic method patent	U.S. Patent 5,401,741
Formulation protection	Concentration and aqueous-solution limitations in dependent claims
Manufacturing protection	Not established by the supplied claims
Device protection	Not established by the supplied claims
Use protection	Strongest aspect of the patent
Current strength	None after expiration

The patent's principal strength was its alignment with the marketed dosage form. A 0.3% aqueous ofloxacin ear drop administered by instillation could satisfy claims 4-6 when used for a claimed otic condition.

Its principal weaknesses were:

reliance on method-of-treatment proof;
broad and potentially contestable terms such as "otopathy" and "effective";
the apparent inconsistency in claim 3;
the unusual dependency structure of claim 7;
lack of apparent protection for the active ingredient itself;
expiration in 2012.

A generic product could have been commercially difficult to distinguish from the reference product if it used the same concentration and route. After expiration, those distinctions no longer provide a patent-based market barrier.

Which companies challenged or competed with ofloxacin otic products?

Ofloxacin otic products competed with several categories of treatment:

generic ofloxacin otic solution;
ciprofloxacin otic products;
ciprofloxacin/dexamethasone combinations;
aminoglycoside-containing otic products;
systemic or oral antibiotics used in selected ear infections;
non-antibiotic treatments for inflammatory or fungal ear conditions.

The principal branded competitive products in the broader otic-antibiotic market included Ciprodex, Cipro HC, and other ciprofloxacin- or aminoglycoside-based products. Those products were not direct infringement substitutes for the claims of U.S. Patent 5,401,741 because the claims require ofloxacin or an ofloxacin salt.

Generic manufacturers could enter with ofloxacin otic solution after addressing FDA requirements for pharmaceutical equivalence, bioequivalence where applicable, manufacturing quality, labeling, and patent certifications. Because the patent was a use patent, labeling strategy was particularly important before expiry.

What patent litigation and settlement issues affected the patent?

The patent's present litigation risk is zero because it expired. No settlement can extend the enforceable life of an expired patent.

For the pre-expiry period, the relevant litigation questions would have been:

Whether a generic applicant filed a Paragraph IV certification.
Whether the patent holder sued within the statutory period.
Whether the generic label included or carved out the patented otic indications.
Whether the patent holder asserted claims 1-6 against the proposed product or against the labeled use.
Whether the patent's claim dependencies created validity or construction issues.
Whether any settlement delayed generic launch beyond the statutory patent term.

The claim text supplied does not establish a specific Paragraph IV defendant, settlement agreement, or reported infringement judgment. The patent's expiration eliminates the need to resolve those issues for current commercialization.

How does ofloxacin otic patent protection compare with competing drugs?

Product or active ingredient	Patent relationship to U.S. 5,401,741	Competitive status
Ofloxacin otic solution	Directly aligned with the claimed method	Generic entry available after expiry
Ciprofloxacin otic solution	Different active ingredient	Separate patent estate
Ciprofloxacin/dexamethasone suspension	Different active ingredients and dosage form	Separate formulation and method patents
Aminoglycoside otic drops	Different active ingredients	Separate product and use protection
Oral ofloxacin	Same active ingredient but different route	Outside the claimed topical otic method
Ofloxacin ophthalmic solution used in the ear	Potentially relevant to method claim if labeled or used otically	Regulatory and infringement analysis depends on actual use

The key distinction is that the patent is route- and use-specific. It does not give the patent owner control over every ofloxacin product or every use of ofloxacin.

What generic launch risks existed?

Before expiration, a generic launch would have faced several risks:

Paragraph IV litigation over otic method claims;
possible induced-infringement allegations based on product labeling;
difficulty carving out otitis media or otitis externa indications;
claim-construction disputes involving "topical," "otopathy," and "effective";
formulation differences affecting pharmaceutical equivalence;
FDA labeling restrictions;
commercial substitution pressure from other otic antibiotics.

After June 18, 2012, the patent-based launch risk ended. Current risks are primarily regulatory, manufacturing, quality, supply, and commercial rather than patent-related.

What geographic coverage did the patent have?

U.S. Patent 5,401,741 provided rights only in the United States. It did not directly block:

manufacture and sale outside the United States;
foreign commercialization;
importation into jurisdictions without corresponding patent rights;
products covered only by foreign patents.

International protection would have depended on separately filed national or regional patents. The U.S. patent's expiration did not determine the expiration of foreign rights.

Did the patent create manufacturing or intellectual-property barriers?

The claims supplied do not cover a manufacturing process. They also do not expressly cover:

synthesis of ofloxacin;
purification;
polymorphism;
particle-size control;
sterile filling;
container-closure systems;
preservatives;
pH adjustment;
packaging;
delivery devices.

The patent could create a use-based barrier for a manufacturer selling an otic product with labeling that directed use within the claims. It did not prevent a company from manufacturing ofloxacin or developing an alternative dosage form as such.

Key Takeaways

U.S. Patent 5,401,741 is a method-of-use patent for topical otic administration of ofloxacin.
Claim 1 is the broadest claim and covers ofloxacin or an ofloxacin salt in a pharmaceutically acceptable carrier.
Claims 4-6 specifically target approximately 0.05%-2% aqueous ofloxacin solutions administered by ear-drop instillation.
The commercial center of gravity is a 0.3% aqueous ofloxacin otic solution.
Claim 3, as supplied, is internally inconsistent because it depends on otitis media but recites otitis externa.
Claim 7 also has an unusual dependency because it appears to combine instillation with intratympanic injection.
The patent expired on June 18, 2012, according to historical FDA product information.
It no longer blocks generic ofloxacin otic entry or current commercialization.
The patent did not claim the ofloxacin molecule, a manufacturing process, or a delivery device.
Ofloxacin otic products are small-molecule products regulated through the NDA/ANDA framework, not the biosimilar pathway.
Current competitive risks are regulatory, quality, manufacturing, supply, and pricing risks rather than patent-exclusion risks.

FAQs About U.S. Patent 5,401,741

Is U.S. Patent 5,401,741 still enforceable?

No. The patent expired in 2012 and cannot presently support an infringement action.

Does the patent cover oral ofloxacin?

No. The claims require topical otic administration. Oral and intravenous ofloxacin regimens fall outside that route limitation.

Does a 0.3% ofloxacin ear drop fall within the patent claims?

Historically, a 0.3% aqueous ofloxacin ear drop administered by instillation would have aligned closely with claims 4-6 when used for a claimed otic condition. The patent is now expired.

Did the patent protect ciprofloxacin ear drops?

No. The claims require ofloxacin or an ofloxacin salt. Ciprofloxacin products are subject to separate patent and regulatory analyses.

Are current generic ofloxacin otic products exposed to this patent?

No. The patent's expiration removed the patent-based exclusion risk. Current products remain subject to FDA approval, quality, labeling, and manufacturing requirements.

References

United States Patent and Trademark Office. (1995). U.S. Patent No. 5,401,741, methods for treating otopathy with ofloxacin. U.S. Department of Commerce. https://patents.google.com/patent/US5401741
U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs and historical labeling for Floxin Otic. U.S. Department of Health and Human Services. https://www.accessdata.fda.gov/scripts/cder/daf/
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. U.S. Department of Health and Human Services. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
Food and Drug Administration. (2024). Orange Book patent and exclusivity information. U.S. Department of Health and Human Services. https://www.fda.gov/drugs/development-resources/patent-and-exclusivity-information
U.S. Code, 21 U.S.C. § 355. (2024). New drugs. Cornell Law School Legal Information Institute. https://www.law.cornell.edu/uscode/text/21/355

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Japan	63-86378	Apr 08, 1988

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	109350	⤷ Start Trial
Australia	3256789	⤷ Start Trial
Australia	614349	⤷ Start Trial
Canada	1330946	⤷ Start Trial
Germany	68917186	⤷ Start Trial
Denmark	168189	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,401,741

Summary for Patent: 5,401,741