US Patent 5,446,070: Claim Scope, Expiration, Litigation Risk, and Patent Landscape for Bioadhesive Topical Compositions

US Patent 5,446,070 covers water-insoluble, water-free or substantially water-free topical compositions that combine a solid active pharmaceutical ingredient, a solvent containing a plasticizer, and a polysaccharide bioadhesive carrier. Its strongest commercial coverage is directed to karaya-gum compositions containing lidocaine base, polyhydric alcohols, and lecithin, together with dual-local-anesthetic compositions containing one anesthetic in free-base form and a second anesthetic as an acid-addition salt.

The patent issued on August 29, 1995. Based on the pre-June 8, 1995 filing regime, its ordinary 17-year patent term would have expired on August 29, 2012, subject to any patent-term adjustment, terminal disclaimer, or earlier loss of rights. It therefore does not present a current US blocking patent, although it remains relevant as prior art and as a historical disclosure for bioadhesive topical drug delivery.

What does US Patent 5,446,070 protect?

The patent claims a platform rather than a single commercial drug product. The platform has four central technical elements:

A therapeutically effective pharmaceutical active ingredient.
A solvent system containing a plasticizer.
A polysaccharide bioadhesive carrier.
A substantially water-free, substantially water-insoluble composition in which the active ingredient is present in non-crystallized form.

Independent claim 1 is the principal platform composition claim. Claims 26 and 31 separately protect mixtures of two local anesthetics, with one anesthetic in base form and the other in acid-addition salt form.

The claim structure is summarized below.

Claim group	Protected subject matter	Main limitations
1-20	Bioadhesive topical composition	Solid active, solvent, plasticizer, polysaccharide carrier, substantially water-free, water-insoluble, non-crystallized active
3, 6-7, 10-12	Local-anesthetic embodiments	Lidocaine and other anesthetics; free base or hydrochloride; polyhydric alcohol solvent
14-16	Narrow lidocaine formulations	Karaya gum, glycols, lidocaine base, lecithin, specified concentration ranges
17-20	Antimicrobial and antifungal embodiments	Clotrimazole and miconazole under the claim 1 composition framework
21-25	Administration method	Contacting skin or mucous membrane with a claim 1 composition
26-30	Dual-anesthetic composition	First anesthetic in base form and different second anesthetic in non-salicylate acid-addition salt form
31-39	Water-free dual-anesthetic composition	Same dual-anesthetic concept, with an expressly water-free carrier
40-45	Dual-anesthetic administration methods	Applying the claim 26 or 31 composition to tissue

How broad is independent claim 1?

Claim 1 is broad in the identity of the active ingredient but narrow in formulation architecture.

Required elements of claim 1

A potentially infringing composition would need to satisfy all of the following limitations:

At least one active pharmaceutical ingredient.
The active must be solid at ambient temperature and pressure.
A pharmaceutically acceptable solvent for the active.
The solvent must constitute about 5% to 70% by weight of the total composition.
The solvent must include about 5% to 50% plasticizer, although the wording creates an interpretive issue concerning whether that range is measured within the solvent or against the total composition.
A polysaccharide bioadhesive carrier at about 20% to 50% by weight.
A substantially water-free composition.
A substantially water-insoluble composition.
Bioadhesion.
The active ingredient must be in non-crystallized form.

The claim does not require a particular dosage form, backing layer, route of administration, active ingredient, particle size, release rate, or manufacturing process. A patch, disk, strip, film, wafer, or molded topical unit could potentially fall within the claim if it satisfies the composition limitations.

Key claim construction issues

The principal infringement questions would concern the following terms:

“Substantially free of water”
“Substantially water insoluble”
“Bioadhesive”
“Non-crystallized form”
“Plasticizer”
“Solvent”
The weight-percent basis for the plasticizer limitation

These terms require technical and potentially prosecution-history analysis. The “non-crystallized form” limitation is especially significant because a product containing crystalline active particles may avoid claim 1 even if the other formulation parameters are met.

Claim 1 also requires the active ingredient to be solid at ambient conditions but non-crystallized in the finished composition. This distinction appears designed to cover molecularly dispersed, amorphous, solubilized, or otherwise non-crystalline active material.

What formulations are protected by claims 14 through 16?

Claims 14 through 16 are the narrowest and most commercially concrete claims.

Claim 14

Claim 14 requires:

20% to 34% karaya gum;
20% to 53% of one or more glycols;
10% to 25% lidocaine base; and
A binder sufficient to bind the ingredients.

Because claim 14 depends on claim 1, the composition must also remain substantially water-free, substantially water-insoluble, bioadhesive, and non-crystalline with respect to the active ingredient.

Claim 15

Claim 15 narrows claim 14 to an approximate formulation containing:

Ingredient	Approximate amount
Karaya gum	30 wt%
Propylene glycol	6 wt%
Dipropylene glycol	15 wt%
Glycerine	15 wt%
Lidocaine base	25 wt%
Lecithin	9 wt%

This claim is materially narrower than claim 1. A competing product using a different bioadhesive, a different binder, a materially different solvent ratio, or a different lidocaine concentration would have a stronger noninfringement position against claim 15, although it could still implicate claim 1 or another patent.

Claim 16

Claim 16 recites approximately:

33% karaya gum;
7% propylene glycol;
12% dipropylene glycol;
An unstated amount of glycerin;
10% lidocaine base; and
5% lecithin.

The supplied text omits the numerical amount for glycerin. That omission creates a potential indefiniteness or clerical-correction issue. The scope of claim 16 would depend heavily on the issued patent, prosecution history, and whether the missing value was corrected in the official record.

How do claims 26 through 45 differ from claim 1?

Claims 26 through 45 create a second claim family centered on dual local anesthetics.

Claim 26 requires:

A first local anesthetic in free-base form;
A different second local anesthetic in non-salicylate acid-addition salt form;
A pharmaceutically acceptable carrier; and
Total anesthetic content of approximately 1% to 50% by weight.

Unlike claim 1, claim 26 does not expressly require:

A polysaccharide carrier;
A plasticizer;
A substantially water-free composition;
A water-insoluble composition;
A non-crystallized active; or
A particular solvent.

That makes claim 26 potentially broader in carrier technology, but narrower in active-ingredient architecture.

Claim 31 adds an express water-free limitation. Claims 27-30 and 32-39 narrow the anesthetic identities, hydrochloride salt form, polyhydric alcohol solvent, polyalkylene glycol solvent, and backing material.

Dual-anesthetic combinations

The claimed first anesthetic may include:

Lidocaine;
Prilocaine;
Benzocaine;
Procaine;
Dyclonine;
Mepivacaine;
Propoxycaine; or
Chloroprocaine.

The second anesthetic may include:

Lidocaine hydrochloride;
Prilocaine hydrochloride;
Tetracaine hydrochloride;
Bupivacaine hydrochloride;
Mepivacaine hydrochloride;
Procaine hydrochloride;
Etidocaine hydrochloride; or
Dibucaine hydrochloride.

The claim requires different anesthetic agents. A formulation containing lidocaine base and lidocaine hydrochloride would therefore face a claim-construction question under the “different” limitation. The safer literal reading is that the two active ingredients must be different molecular anesthetics, not merely different salt forms of the same anesthetic.

What drug classes are covered?

Claim 4 contains a very broad Markush listing of pharmaceutical classes. It includes analgesics, anti-inflammatory agents, central nervous system drugs, antihistamines, steroids, respiratory drugs, cardiovascular drugs, antimicrobials, hormones, vitamins, antitumor agents, enzymes, peptides, antidiabetics, antidepressants, antimalarials, antiulcer drugs, and other categories.

Claim 5 narrows the disclosure to steroid compounds, including testosterone, estradiol compounds, progesterone, norethindrone, medroxyprogesterone acetate, megestrol acetate, and related steroids.

Claims 17-20 identify antimicrobial and antifungal embodiments, including clotrimazole and miconazole. Those claims do not independently cover a conventional cream or aqueous gel. They remain dependent on the claim 1 architecture, including the bioadhesive carrier, solvent/plasticizer system, substantially water-free condition, water insolubility, and non-crystallized active.

What is the patent expiration date?

The patent issued on August 29, 1995. For a US application filed before June 8, 1995, the governing term was generally 17 years from issuance rather than 20 years from the earliest effective nonprovisional filing date. On that basis, the ordinary expiration date was August 29, 2012.

Event	Date
US patent grant	August 29, 1995
Ordinary 17-year term endpoint	August 29, 2012
Current status	Expired by term, absent an unusual term adjustment or other record-specific event

The expiration eliminates ordinary patent-enforcement risk for US products launched after the term ended. The patent can still matter as prior art against later applications, especially applications claiming karaya-gum, non-crystalline active, water-free bioadhesive systems or mixed anesthetic salt/base formulations.

What is the Orange Book status of US Patent 5,446,070?

US Patent 5,446,070 is not, by its technical subject matter alone, an Orange Book-listed patent. Orange Book listing depends on an approved new drug application and the patent’s relationship to the approved drug product, formulation, method of use, or active ingredient.

The patent claims a broad topical delivery platform and does not identify a particular FDA-approved product in the claims supplied. Its Orange Book relevance therefore cannot be inferred from the patent number alone. A patent may be expired, unlisted, or both, and patent status under the Orange Book is separate from validity under general patent law. The FDA publishes listed patents and exclusivity information through the Approved Drug Products with Therapeutic Equivalence Evaluations, commonly called the Orange Book (FDA, 2025).

Did the patent create Paragraph IV risk?

The patent could have created Paragraph IV risk only if it had been listed for an approved reference product and a generic applicant sought approval for a product covered by the listed claims.

Because the patent expired in 2012, it does not create a current Paragraph IV blocking period. A modern abbreviated new drug application directed to a topical lidocaine or antifungal product would instead face:

Current Orange Book patents, if any;
Formulation and device patents filed after 1995;
Method-of-use patents;
Non-patent regulatory exclusivity;
FDA requirements for demonstrating pharmaceutical equivalence and bioequivalence or comparative performance.

The expired patent remains relevant to obviousness and written-description analysis. A later patent that claims a karaya-gum bioadhesive with lidocaine, glycols, lecithin, and a non-crystalline active would need meaningful technical distinctions from the disclosure of US 5,446,070.

What patent landscape surrounds the invention?

The relevant landscape has four technical clusters.

Bioadhesive oral and mucosal systems

This group includes gum-based, cellulose-based, alginate-based, carbomer-based, and polymeric films that adhere to oral mucosa or skin. Later patents commonly distinguish themselves through:

Specific polymer combinations;
Controlled dissolution or erosion;
Mucoadhesive strength;
Drug-release kinetics;
Backing layers;
Permeation enhancers;
Improved taste or mouthfeel;
Manufacturing methods; and
Defined residual-water limits.

US 5,446,070 is strongest as an early platform disclosure for a substantially water-free polysaccharide matrix containing a dissolved or molecularly dispersed active.

Topical local-anesthetic products

The competitive field includes lidocaine creams, gels, ointments, sprays, patches, oral films, dental disks, and compounded mucosal systems. The patent’s differentiated concept is the combination of:

Lidocaine base;
Polyhydric alcohol solvent;
Karaya gum;
Lecithin binder;
Low or absent water; and
Non-crystalline active.

A product using lidocaine hydrochloride in an aqueous hydrogel would sit outside several important limitations of claims 1 and 14-16, although it could implicate unrelated patents.

Dual-base and salt anesthetic systems

Claims 26-45 are directed to a formulation strategy that combines a lipophilic free-base anesthetic with a more water-compatible acid-addition salt. The intended technical effect is likely a balance between tissue partitioning, dissolution, local concentration, and delivery from a topical carrier.

Later patentability would turn on whether the claimed combination produces an unexpected release, penetration, stability, or anesthetic-duration result. A simple substitution of one anesthetic salt or polyol for another would face a stronger obviousness challenge than a formulation supported by comparative pharmacokinetic or tissue-penetration data.

Antifungal bioadhesive systems

Claims 17-20 extend the platform to clotrimazole and miconazole. Later antifungal patents are more likely to focus on:

Vaginal or oral mucosal delivery;
Extended residence time;
Treatment of candidiasis;
Specific particle or amorphous states;
Enhanced dissolution of poorly soluble antifungals;
Release over a defined period; and
Applicator or dosage-form design.

The patent does not provide product-specific clinical or regulatory protection for every clotrimazole or miconazole formulation. The claim limitations must be met in combination.

How strong is the patent estate?

As a current enforcement estate, it is weak because the patent has expired. As an historical disclosure, it was technically broad but commercially concentrated.

Factor	Assessment
Composition breadth	Broad for active identity; narrower for carrier and physical-state limitations
Local-anesthetic coverage	Strongest commercial focus
Lidocaine formulation coverage	Narrow but concrete in claims 14-16
Dual-anesthetic coverage	Broader carrier scope, narrower active-form requirement
Manufacturing coverage	Limited; no substantial process-claim platform is apparent
Method-of-use coverage	Broad contact-based administration claims, but dependent on composition limitations
Current blocking power	None after expiration
Prior-art significance	High for later water-free bioadhesive and dual-anesthetic formulations
Orange Book value	Not established by the patent claims alone
Biosimilar relevance	None; the patent concerns small-molecule topical compositions

What generic launch scenarios would have existed?

Before expiration, a competing product could have reduced claim risk through several design strategies:

Use an aqueous formulation rather than a substantially water-free composition.
Use a non-polysaccharide adhesive or a non-adhesive carrier.
Maintain the active in crystalline form.
Replace karaya gum with a different polymer.
Use a single anesthetic rather than a base-plus-salt combination.
Use the same anesthetic in a different chemical form while avoiding the “different second anesthetic” limitation.
Change the solvent and plasticizer concentrations outside the claimed ranges.
Use a conventional cream, gel, spray, or ointment rather than a finite bioadhesive dosage unit.

These strategies could avoid literal infringement but would not necessarily avoid infringement of unrelated continuation, improvement, formulation, device, or method patents.

What manufacturing and IP barriers remain?

The expired patent does not block manufacture. The principal technical barriers are now formulation and regulatory rather than exclusivity barriers:

Achieving a stable non-crystalline active;
Maintaining adhesion without excessive swelling;
Controlling solvent migration;
Preventing recrystallization during storage;
Reproducing uniform drug content;
Controlling mucosal irritation;
Establishing shelf life;
Demonstrating performance for a topical or mucosal product; and
Meeting FDA requirements for the selected regulatory pathway.

For lidocaine, the regulatory route depends on the product type and intended use. A topical product may be regulated as an OTC drug, prescription drug, or drug-device combination depending on formulation, indication, delivery mechanism, and labeling. The expired patent does not determine the FDA pathway.

Key Takeaways

US Patent 5,446,070 covers water-free or substantially water-free bioadhesive topical compositions.
Claim 1 requires a solid active in non-crystallized form, a solvent/plasticizer system, a polysaccharide carrier, bioadhesion, and substantial water insolubility.
Claims 14-16 focus on karaya gum, glycols, lidocaine base, lecithin, and specific formulation ranges.
Claims 26-45 separately cover dual-local-anesthetic compositions using a free base and a different acid-addition salt.
Claims 17-20 extend the platform to clotrimazole and miconazole, but only within the full claim 1 formulation framework.
The patent issued August 29, 1995, and its ordinary patent term expired August 29, 2012.
The patent has no current US blocking effect, but it remains relevant prior art for later bioadhesive, amorphous-drug, and dual-anesthetic patents.
Orange Book listing and Paragraph IV relevance cannot be inferred from the patent claims alone.
The principal surviving commercial risks would come from later patents covering specific products, devices, methods, formulations, or manufacturing processes.

FAQs

Does US Patent 5,446,070 cover all lidocaine patches?

No. It covers only compositions meeting the claim limitations, including the specified solvent, bioadhesive, water-content, water-solubility, and non-crystalline-active requirements. Many lidocaine patches use different polymers, drug forms, or release systems.

Does the patent cover lidocaine hydrochloride by itself?

Claims 1, 3, 6, and 7 can encompass local anesthetic acid-addition salts, including hydrochloride forms, if all inherited composition limitations are satisfied. The narrower lidocaine claims 14-16 specifically identify lidocaine base rather than lidocaine hydrochloride.

Is karaya gum required in every claim?

No. Karaya gum is required by the narrower claims that expressly recite it, especially claims 9, 14, 15, and 16. Claim 1 broadly covers polysaccharide bioadhesives, and claims 26-45 use a more general carrier formulation.

Can a formulation containing crystalline lidocaine avoid claim 1?

Potentially, because claim 1 requires the active to be present in non-crystallized form. The product’s actual solid-state characterization, including whether crystalline material is present and in what proportion, would control the analysis.

Are the antifungal claims still enforceable against clotrimazole products?

No, not as a matter of this expired US patent. Claims 17-20 may remain relevant as prior art, but they do not provide current patent enforcement rights after expiration.

Sources

United States Patent and Trademark Office. (1995). US Patent No. 5,446,070, Bioadhesive compositions for topical application.
United States Patent and Trademark Office. (n.d.). Manual of Patent Examining Procedure § 2710: Term of patent.
U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations.
U.S. Food and Drug Administration. (2024). Listing of patent information in the Orange Book.

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

Details for Patent: 5,446,070

Summary for Patent: 5,446,070