US Patent 5,234,957: Claim Scope, Expiration, and Patent Landscape for Topical Bioadhesive Anesthetic Compositions

US Patent 5,234,957 covers substantially water-insoluble, low-water topical compositions containing a local anesthetic, a solvent, and a flexible polysaccharide or related bioadhesive carrier. The core technical concept is a solvent-containing bioadhesive dosage form that remains on a topical surface and releases anesthetic locally.

The patent issued on August 10, 1993. Because it was filed before June 8, 1995, its term was generally governed by the 17-year-from-issue framework applicable to pre-1995 applications. On that basis, the patent expired in August 2010, subject to any adjustment or terminal-disclaimer information recorded in the official prosecution file. The claims therefore do not present a current blocking patent risk in the United States. The patent also is too old to support a current Orange Book exclusivity position.

What does US Patent 5,234,957 protect?

The independent claims protect two related composition architectures:

Claim	Protected subject matter	Principal limitations
1	Single-anesthetic topical composition	Local anesthetic, solvent at about 5%-70% by weight, flexible finite bioadhesive carrier at about 20%-50%, less than 10% water, substantially water insoluble
11	Dual-anesthetic topical composition	First anesthetic in base form, different second anesthetic in acid-addition-salt form, solvent at about 5%-70%, bioadhesive carrier at about 20%-50%, substantially water-free and water insoluble

Claim 1 is the principal single-agent claim. Claim 11 is an independent dual-agent claim and is materially narrower in one respect because it requires:

Two different local anesthetics;
One anesthetic in base form; and
The other anesthetic in acid-addition-salt form.

The patent does not broadly claim every topical lidocaine product, every anesthetic patch, or every bioadhesive formulation. A potentially infringing product would need to satisfy the claimed composition elements and the quantitative ranges.

How should claim 1 be construed?

Claim 1 requires all of the following:

A composition intended for topical application;
A therapeutically effective amount of at least one local anesthetic;
A pharmaceutically acceptable solvent;
Solvent concentration of approximately 5% to 70% by weight;
A flexible, finite, pharmaceutically acceptable polysaccharide bioadhesive carrier;
Carrier concentration of approximately 20% to 50% by weight;
Less than 10% water;
Substantial water insolubility; and
Bioadhesion.

The claim is composition-focused. It does not require a particular manufacturing process, release rate, treatment duration, disease indication, applicator, or commercial product configuration.

What is the significance of the “flexible, finite” carrier limitation?

The carrier must be a discrete or finite dosage-form material rather than merely a dissolved thickener or an unlimited bulk vehicle. “Flexible” points toward a conformable film, strip, disc, patch, wafer, or similar dosage form.

The specification and dependent claims indicate that the carrier can include gums, celluloses, cellulose derivatives, polyacrylates, and polyacrylic acids. Claim 1 itself is narrower than a generic “bioadhesive” claim because it requires a polysaccharide carrier. Claim 16, which depends from claim 11, expressly adds polyacrylates and polyacrylic acids to the dual-anesthetic embodiment.

What does “substantially water insoluble” add?

The formulation must resist dissolution in water. That limitation differentiates the claimed dosage form from conventional aqueous gels, rinses, sprays, and water-soluble films.

The claim also requires less than 10% water. Claims 22 and 23 narrow this requirement to less than 5% and less than 3%, respectively. These dependent claims create progressively stricter low-moisture embodiments:

Claim	Water limitation
1	Less than 10% by weight
22	Less than 5% by weight
23	Less than 3% by weight

A formulation containing 8% water could potentially satisfy claim 1 but would not satisfy claims 22 or 23. A formulation containing 2% water could satisfy all three water-content limitations, assuming the other limitations are met.

Which anesthetics and solvents fall within the claims?

Claim 2 identifies a broad group of local anesthetics:

Procaine
Lidocaine
Prilocaine
Mepivacaine
Dyclonine
Dibucaine
Benzocaine
Chloroprocaine
Tetracaine
Bupivacaine
Etidocaine

Claim 3 permits the anesthetic to be present as the free base, an acid-addition salt, or both. Claim 4 identifies hydrochloride salts as a specific embodiment.

The solvent claims focus on polyhydric alcohols and polyalkylene glycols. Claim 9 lists:

Dipropylene glycol
Propylene glycol
Ethylene glycol
Polyethylene glycol
Glycerin
Butylene glycol
Hexylene glycol
Polypropylene glycol
Sorbitol

The listing of specific anesthetics and solvents in dependent claims does not mean that claim 1 is limited to those exact compounds. Claim 1 uses the broader categories “local anesthetic,” “pharmaceutically acceptable solvent,” and “polysaccharide bioadhesive carrier.” The dependent claims provide fallback positions and narrower species.

What bioadhesive carriers are protected?

The carrier coverage is broad within the stated material classes. The claims identify:

Karaya gum
Tragacanth gum
Pectin gum
Xanthan gum
Guar gum
Cellulose
Cellulose derivatives
Polyacrylates
Polyacrylic acids

Claims 5 and 6 apply to the single-anesthetic branch. Claims 16 and 17 apply to the dual-anesthetic branch.

The most commercially relevant carrier limitations are likely the combination of:

A finite flexible dosage form;
A polysaccharide or related polymer matrix;
Low water content;
A polyhydric alcohol solvent; and
A local anesthetic dissolved or dispersed in the matrix.

A product using a conventional aqueous carbomer gel would face a stronger argument that it fails the finite-carrier, low-water, and water-insolubility limitations. A dry or semidry adhesive film containing glycerin or propylene glycol and lidocaine would present a closer technical profile.

How do claims 1 and 11 compare?

Claim 1 is broader regarding the number and form of anesthetic agents. It requires at least one local anesthetic and permits the anesthetic to be in base form, salt form, or both.

Claim 11 requires two different agents and specifies their chemical forms. It may be harder to satisfy, but it protects a distinct formulation strategy in which a free-base anesthetic and an acid-addition salt are combined in the same low-water adhesive carrier.

Issue	Claim 1	Claim 11
Number of anesthetics	At least one	Two different agents
Chemical form	Base, salt, or both under dependent claims	One base and one acid-addition salt
Carrier	Flexible finite bioadhesive carrier	Same general requirement
Solvent	5%-70% by weight	5%-70% by weight
Carrier concentration	20%-50% by weight	20%-50% by weight
Water	Less than 10%	Substantially free of water
Water insolubility	Expressly required	Expressly required

Claim 11 may have been designed to address compatibility, solubility, or release characteristics created by combining anesthetic forms. Its scope is not a general claim to any two-anesthetic topical product.

What does the backing-material limitation cover?

Claims 10 and 21 add a backing material that conforms to the size and shape of a single dosage of the composition.

This limitation covers a dosage-form construction in which the adhesive anesthetic composition is supported by a backing layer. Potential examples include:

A polymeric backing film;
A foil or laminate;
A fabric-backed patch;
A shaped oral or dermal strip; or
A backing layer cut to the unit-dose geometry.

The backing must conform to the size and shape of a single dose. A bulk container of adhesive gel would not naturally satisfy this limitation. The backing claims are therefore narrower product-form claims, not independent protection for every composition within claim 1 or claim 11.

When did US Patent 5,234,957 lose exclusivity?

The patent issued on August 10, 1993. For a pre-June 8, 1995 application, the applicable patent term was generally 17 years from issuance rather than 20 years from the earliest effective nonprovisional filing date. The ordinary term therefore ended in August 2010, absent a recorded adjustment that changed the date. [1][2]

The practical consequences are:

No current US patent exclusion based solely on US 5,234,957;
No current ability to bring a new infringement action based on unexpired claims;
No current Paragraph IV exposure directed solely to this patent;
No meaningful patent-based barrier to generic or follow-on development; and
No current Orange Book patent listing significance.

Patent expiration does not erase historical infringement exposure occurring during the enforceable term. It does eliminate prospective exclusion after expiration.

What is the Orange Book status of US Patent 5,234,957?

US Patent 5,234,957 should not be treated as a current Orange Book-listed patent. The Orange Book lists patents submitted by new drug application sponsors for approved drug products, including qualifying drug substance, drug product, and method-of-use patents. A patent covering a general topical composition does not automatically qualify for listing. [3]

The patent claims a formulation platform rather than a specifically identified FDA-approved active ingredient product. Unless it was historically submitted and accepted for a particular NDA, there is no basis to infer Orange Book listing from the patent claims alone.

For a current product, the relevant regulatory analysis would instead involve:

The approved NDA or abbreviated new drug application;
Any listed patents for the specific product;
FDA labeling;
Drug product exclusivity;
Potential monograph status; and
Whether the product is regulated as a drug, device, or combination product.

Are Paragraph IV challenges relevant?

A Paragraph IV certification would have been relevant only if:

A generic applicant submitted an ANDA referencing an NDA product;
US Patent 5,234,957 was listed in the Orange Book for that reference product; and
The patent remained unexpired when the ANDA certification was made.

Because the patent expired in 2010, it cannot now create a prospective Paragraph IV barrier. A generic applicant would not need to wait for the patent term to expire. If the patent had been listed historically, its expiration would have removed the relevant patent-based delay mechanism.

The patent also does not appear, from the claims supplied, to be directed to a biologic or biological product. Biosimilar litigation and the Biologics Price Competition and Innovation Act therefore are not central to this patent.

What patent litigation or settlements affect this patent?

The supplied claims do not identify a litigation history, settlement agreement, license, or Paragraph IV case. The patent’s 1993 issue date and 2010 expiration date make current litigation unlikely. Any historical dispute would need to be tied to a particular product, licensee, formulation, or prosecution event.

There is no basis to infer that a settlement agreement created post-expiration restrictions. A private license may have affected historical commercialization, but it would not revive the expired patent or create patent exclusivity after expiration.

How strong was the patent estate?

The patent was technically focused but commercially constrained by several cumulative limitations:

Low water content;
Substantial water insolubility;
A flexible finite carrier;
A defined solvent range;
A defined carrier range;
Bioadhesion; and
For claim 11, two different anesthetic forms.

Its strongest coverage would have been directed to unit-dose adhesive films, wafers, patches, or discs containing a local anesthetic in a low-water polyol-polymer matrix.

Its weaker areas would have included:

Conventional aqueous gels;
Sprays and rinses;
Bulk creams;
Products without a finite carrier;
Products with carrier levels below 20% or above 50%;
Products with solvent levels outside 5%-70%;
Water-soluble dosage forms; and
Products using a single anesthetic where claim 11 was the only potentially relevant claim.

The patent’s commercial value was therefore dependent on the specific dosage-form architecture rather than the anesthetic molecule itself. Lidocaine, benzocaine, prilocaine, and related anesthetics were known pharmaceutical agents and were not monopolized by this patent as active ingredients.

What generic launch and freedom-to-operate risks exist today?

For US development, the patent creates no current patent-expiration barrier. A developer can use the claimed composition concept without infringing an unexpired US claim from this patent.

The remaining risks are product-specific:

Other patents covering adhesive matrices;
More recent patents covering oral films, dermal patches, or mucosal delivery;
Formulation patents directed to particular polymer combinations;
Device patents covering applicators or backing structures;
Method-of-use patents;
Trade-secret manufacturing processes; and
Regulatory exclusivity unrelated to this patent.

A launch assessment should not rely on the expiration of US 5,234,957 alone. The patent is expired, but later continuation, divisional, improvement, or foreign-family patents could have covered related commercial products. Those rights must be evaluated separately by jurisdiction and claim family.

How does this patent compare with modern topical anesthetic patents?

US 5,234,957 is an early formulation-platform patent. Its claims emphasize composition percentages, solvent selection, low moisture, and bioadhesive structure.

Modern topical anesthetic patent estates typically separate protection into several categories:

Patent category	Typical focus
Active ingredient	New anesthetic molecule or salt
Formulation	Particle size, solvent system, pH, permeation enhancer
Delivery platform	Film, microneedle, patch, mucoadhesive disc
Manufacturing	Drying, coating, lamination, solvent removal
Method of use	Treatment of a specific pain condition or procedure
Device	Applicator, reservoir, backing, release-control structure

The 5,234,957 claims principally occupy the formulation and delivery-platform categories. They do not claim a new anesthetic, a specific indication, or a detailed manufacturing process.

Key Takeaways

US Patent 5,234,957 covers low-water, substantially water-insoluble topical anesthetic compositions using a flexible finite bioadhesive carrier.
Claim 1 targets a single-anesthetic formulation with 5%-70% solvent and 20%-50% carrier.
Claim 11 targets a dual-anesthetic formulation combining a free base and a different acid-addition salt.
The patent identifies lidocaine, benzocaine, prilocaine, mepivacaine, tetracaine, bupivacaine, and other local anesthetics.
Key solvents include glycerin, propylene glycol, polyethylene glycol, sorbitol, and related polyhydric alcohols.
Claims 10 and 21 add a unit-dose backing material.
Claims 22 and 23 narrow the water content to less than 5% and less than 3%.
The patent issued August 10, 1993 and generally expired in August 2010 under the pre-1995 patent-term rules.
It does not create a current US blocking position, current Paragraph IV risk, or current Orange Book exclusivity barrier.
Current freedom-to-operate analysis must focus on later patents, continuation families, product-specific patents, manufacturing rights, and non-US rights.

FAQs About US Patent 5,234,957

Does US Patent 5,234,957 cover lidocaine gel?

No. It covers a specific class of topical compositions. A lidocaine gel would need to satisfy the solvent, carrier, water, water-insolubility, bioadhesion, and finite-carrier limitations of the relevant claim.

Does the patent cover an ordinary lidocaine patch?

Only if the patch has the claimed composition architecture, including the specified solvent and carrier ranges, low water content, substantial water insolubility, and bioadhesive characteristics. The patent does not cover every lidocaine patch.

Are claims 22 and 23 independent claims?

No. They depend from claim 1. They narrow the water content to less than 5% and less than 3%, respectively.

Can an expired patent still be listed in the Orange Book?

A patent can remain in historical records, but an expired patent cannot provide a current patent-term barrier to an ANDA launch. Orange Book relevance also depends on whether the patent was properly listed for a specific approved drug product.

Does the patent cover manufacturing methods?

The claims supplied are composition claims. They do not independently claim a manufacturing process, drying process, coating process, or lamination method.

References

United States Patent and Trademark Office. (1993). US Patent No. 5,234,957: Bioadhesive compositions for topical application.
United States Patent and Trademark Office. (n.d.). Manual of Patent Examining Procedure, Section 2710: Patent term.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. [no URL provided]

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	002355	⤷ Start Trial
Austria	122240	⤷ Start Trial
Austria	144704	⤷ Start Trial
Austria	148633	⤷ Start Trial
Austria	223185	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,234,957

Summary for Patent: 5,234,957