U.S. Patent 5,676,968: Scope, Claims, Expiration, and Transdermal Patent Landscape

U.S. Patent 5,676,968 covers a multilayer transdermal therapeutic system in which an active ingredient is incorporated into an adhesive matrix containing 0.1% to 40% by weight of a vinylpyrrolidone-vinyl acetate copolymer as a crystallization inhibitor. The patent also claims selected active ingredients, penetration enhancers, backing films, matrix dimensions, protective liners, active-ingredient loading, and polyacrylate adhesives.

The patent issued on October 14, 1997, and its enforceable term has expired. Based on the pre-1995 U.S. filing framework applicable to the patent, the expected expiration date was October 14, 2014, subject to any applicable patent-term adjustment or extension. The patent therefore presents historical technology and freedom-to-operate relevance, but it does not currently block commercial development in the United States. [1][2]

What does U.S. Patent 5,676,968 protect?

The patent protects a transdermal patch having two required functional layers:

An impermeable top coating containing or associated with a penetration enhancer and active ingredient.
An adhesive matrix attached to the top coating.

The adhesive matrix must contain:

The active ingredient;
0.1% to 40% by weight of a vinylpyrrolidone-vinyl acetate copolymer; and
A skin-contact adhesive.

The central technical concept is the use of the vinylpyrrolidone-vinyl acetate copolymer to inhibit crystallization of the active ingredient in the adhesive matrix. The crystallization inhibitor is therefore a required limitation of independent claim 1, not merely an optional excipient.

Patent identification

Field	Information
U.S. patent	5,676,968
Title	Transdermal therapeutic system
Issue date	October 14, 1997
Technology	Adhesive-matrix transdermal delivery
Principal formulation feature	Vinylpyrrolidone-vinyl acetate copolymer as crystallization inhibitor
Key adhesive type	Polyacrylate, under claim 10
Key dosage form	Multilayer transdermal patch
Expected U.S. expiration	October 14, 2014
Current enforceability	Expired
Regulatory category	Drug-delivery technology, not a standalone drug approval

The patent is associated with the Lohmann transdermal delivery technology portfolio. Patent records identify a German-origin priority chain and a U.S. patent family directed to transdermal systems using polymeric crystallization control. [1]

How broad is independent claim 1?

Claim 1 is broad in active-ingredient selection but narrow in its structural and polymer requirements.

Claim 1 element analysis

Claim limitation	Scope	Practical significance
Transdermal therapeutic system	Requires a system designed to deliver an active ingredient through skin	Excludes oral tablets, injectables, ordinary topical creams, and non-transdermal dosage forms
Top coating impermeable to water	Requires a water-impermeable backing or top layer	The top coating functions as a backing layer and limits water transmission
Penetration enhancer and active ingredient associated with top coating	Requires both components in the claimed top-coating arrangement	Could create a dispute over whether the enhancer must be physically present in the backing layer or merely part of the top-coating structure
Adhesive matrix adhered to top coating	Requires direct or operative attachment between matrix and top coating	A reservoir system with a separate non-adhesive drug compartment may fall outside the claim
Active ingredient in matrix	Requires the active ingredient to be present in the adhesive matrix	A patch with drug only in a separate reservoir may avoid this limitation
0.1%-40% vinylpyrrolidone-vinyl acetate copolymer	Mandatory quantitative polymer limitation	This is the principal composition-based limitation
Skin-contact adhesive	Requires adhesive contact with the skin	A non-adhesive patch using straps or mechanical retention may avoid claim 1

The claim does not require a specific active ingredient, dose, release rate, therapeutic indication, or commercial product. Its breadth comes from the generic formulation architecture. Its principal vulnerability is that infringement requires proof of the specified copolymer concentration and the claimed layer arrangement.

What do dependent claims 2 through 10 add?

The dependent claims create narrower species within claim 1. They do not broaden the independent claim.

Claims 2 and 3: active-ingredient classes

Claim 2 identifies a steroid hormone as the active ingredient. Claim 3 lists additional classes, including:

Steroid hormones;
Corticoids;
Ergoline compounds;
Antihypertensive compounds;
Anticoagulants;
Psychopharmacological agents;
Organic nitro compounds;
Beta blockers;
Carotenoids;
Beta-carboline compounds;
Scopolamine;
Mixtures of those compounds.

The supplied text states "asteroid hormone" in claim 2. That phrase appears to be a transcription or OCR error for "steroid hormone." The issued patent should control any legal interpretation.

Claim 3 is unusual because it repeats steroid hormones and contains a broad list of pharmacological classes. It remains dependent on claim 1 and therefore requires the same backing, matrix, copolymer, and adhesive limitations.

Claim 4: penetration enhancer in the adhesive matrix

Claim 4 adds a penetration enhancer to the adhesive matrix. Claim 1 already refers to a penetration enhancer in the top-coating arrangement. Claim 4 therefore appears to require penetration-enhancer presence in both locations, depending on the construction of claim 1.

Examples of potential penetration enhancers in transdermal technology include alcohols, fatty acids, fatty acid esters, glycols, terpenes, and sulfoxides. The claim does not restrict the enhancer to a named chemical class.

Claim 5: removable protective layer

Claim 5 requires a removable protective layer over the adhesive matrix. This is the conventional release liner removed before application to the skin.

A product without a removable liner could avoid claim 5 but would remain potentially relevant to claim 1 if all independent-claim limitations were present.

Claim 6: active-ingredient concentration

Claim 6 limits the active ingredient in the matrix to 0.1% to 10% by weight relative to total matrix weight.

This claim is narrower than claim 1 because it adds a concentration range. A formulation containing more than 10% active ingredient could still fall within claim 1, provided it satisfies all other limitations.

Claims 7 and 8: top-coating materials and thickness

Claim 7 limits the top coating to films made from:

Polyvinyl chloride;
Polyvinylidene chloride;
Ethylene-vinyl acetate copolymer;
Polyethylene;
Polyester;
Copolymers of those materials; or
Coextrudates.

Claim 8 narrows the top-coating thickness to 10-100 micrometers.

These claims create a materials-based patent position around conventional polymeric backing films. A metal foil, fluoropolymer, multilayer laminate outside the listed polymer classes, or another non-covered backing structure could avoid these dependent claims while remaining subject to claim 1.

Claim 9: matrix dimensions

Claim 9 requires:

Matrix thickness of 20-500 micrometers; and
Opposite-face surface area of 5-100 square centimeters.

The surface-area limitation is material for product-specific infringement. A smaller patch, larger patch, or matrix outside the claimed thickness range could avoid claim 9 but not necessarily claim 1.

Claim 10: polyacrylate adhesive

Claim 10 limits the skin-contact adhesive to a polyacrylate.

This claim is commercially relevant because polyacrylate pressure-sensitive adhesives are common in drug-in-adhesive transdermal patches. It is not limited to a named polyacrylate grade, monomer composition, crosslinking system, or commercial supplier.

What patent claims form the core of the estate?

The effective patent estate is concentrated in one issued U.S. patent and one central independent claim. The commercial value of the claim set historically came from claim 1, not from a broad collection of independent claims.

Claim group	Protected subject matter	Relative breadth
Claim 1	General adhesive-matrix patch with vinylpyrrolidone-vinyl acetate copolymer	Broadest and commercially central
Claims 2-3	Specified drug classes	Narrower active-ingredient species
Claim 4	Penetration enhancer in matrix	Narrower formulation configuration
Claim 5	Removable protective liner	Conventional patch construction
Claim 6	0.1%-10% matrix drug concentration	Narrower concentration range
Claims 7-8	Listed backing polymers and 10-100 micrometer thickness	Narrower structural species
Claim 9	Matrix dimensions and area	Product-dimension limitations
Claim 10	Polyacrylate adhesive	Narrower adhesive species

No claim, based on the supplied claim set, independently protects a particular drug product. The patent instead claims a platform delivery system that could be used with several therapeutic categories.

When did U.S. Patent 5,676,968 lose exclusivity?

The patent lost enforceable exclusivity no later than October 14, 2014, based on the ordinary 17-year term from its October 14, 1997, issue date under the pre-1995 U.S. patent-term rules. U.S. patent law later shifted to a 20-year term measured from the earliest effective nonprovisional filing date, but patents in the relevant filing category generally remained governed by the earlier regime. [2]

Exclusivity timeline

Event	Date
German-origin priority period	1992
International/U.S. prosecution period	Early to mid-1990s
U.S. patent grant	October 14, 1997
Expected ordinary expiration	October 14, 2014
Current status	Expired

No current patent-term extension should be expected for the patch platform itself. Patent-term extension under 35 U.S.C. § 156 is generally tied to regulatory review of a specific approved product and is not automatically available to a general delivery-platform patent. [2]

What is the Orange Book status of U.S. Patent 5,676,968?

U.S. Patent 5,676,968 should not be treated as an active Orange Book barrier by itself.

The FDA Orange Book lists patents submitted by NDA applicants or holders for approved drug products. A formulation or delivery-system patent may appear in the Orange Book only when the NDA holder submits it for a particular approved product and the FDA accepts the listing under applicable requirements. A general transdermal-platform patent is not automatically listed merely because it covers a possible drug-delivery configuration. [3]

Because the patent expired in 2014, it cannot presently support a new effective Paragraph IV exclusivity strategy. Any historical Orange Book listing would no longer create a live patent bar to ANDA approval.

How do Paragraph IV challenges apply?

A Paragraph IV certification would have been relevant only if:

The patent were listed in the Orange Book for the reference drug;
The proposed generic product implicated the listed claims; and
The patent remained unexpired or otherwise enforceable.

For a generic transdermal product, the applicant could challenge the patent by asserting that:

The product lacks vinylpyrrolidone-vinyl acetate copolymer;
The copolymer concentration is below 0.1% or above 40%;
The active ingredient is not in the adhesive matrix;
The backing is not impermeable to water;
The product uses a reservoir rather than the claimed adhesive matrix;
The penetration enhancer is absent from the claimed location;
The adhesive is not a skin-contact adhesive; or
The claim is invalid for anticipation, obviousness, indefiniteness, or lack of enablement.

Because the patent is expired, present-day ANDA applicants would generally address it as expired rather than mount a commercially meaningful Paragraph IV campaign.

What generic launch risks exist for transdermal products?

The patent creates no current U.S. launch risk. Its historical importance was greatest for products using all of the following:

A drug-in-adhesive matrix;
A water-impermeable polymer backing;
A polyacrylate pressure-sensitive adhesive;
A vinylpyrrolidone-vinyl acetate copolymer at a concentration within the claimed range;
A penetration enhancer;
An active ingredient dissolved or dispersed in the matrix.

A generic developer can now use that architecture without infringing this patent. Other risks may arise from later patents covering:

The specific active ingredient;
A particular patch brand;
A release-rate profile;
A specific adhesive composition;
A manufacturing process;
A multilayer laminate;
A therapeutic method of use;
A combination with another active ingredient;
A particular concentration or dosing schedule.

The expired patent does not eliminate those later or separate rights.

What formulations are protected by the patent?

The patent is most directly relevant to adhesive-matrix formulations in which the active ingredient has a tendency to crystallize during storage or use. The copolymer is claimed as a crystallization inhibitor, allowing the matrix to maintain a usable drug distribution.

A formulation is most exposed to the historical claim scope when it includes:

Formulation attribute	Relevance
Drug in adhesive matrix	Required by claim 1
Vinylpyrrolidone-vinyl acetate copolymer	Required by claim 1
Polymer concentration of 0.1%-40%	Required by claim 1
Polyacrylate adhesive	Claim 10
Drug loading of 0.1%-10%	Claim 6
Penetration enhancer in matrix	Claim 4
Conventional polymer backing	Claims 7-8
Removable release liner	Claim 5

The patent does not require a specific crystallization assay, particle-size distribution, dissolution profile, or adhesive peel-strength value. Those omissions increase the claim’s formulation breadth but may create validity questions if prior art disclosed comparable polymer-stabilized matrices.

How strong is the patent estate?

The current legal strength is zero for enforcement because the patent has expired. Its historical claim strength was mixed.

Strengths

Claim 1 covers a platform rather than one drug.
The active ingredient is defined generically.
The copolymer range extends from 0.1% to 40%.
The claim covers common transdermal patch architecture.
Dependent claims provide multiple formulation and construction positions.

Weaknesses

The claim requires a specific polymer family and quantitative range.
The layer arrangement may distinguish between adhesive-matrix and reservoir systems.
Several dependent claims use conventional patch components.
Prior art on drug-in-adhesive patches, polymeric crystallization inhibitors, and penetration enhancers could support validity attacks.
The patent contains no live term in the United States.

The patent is therefore best viewed as an expired platform patent with historical licensing and litigation relevance, not as a current barrier to entry.

Which companies are challenging the patent?

No current challenge is legally material because the patent expired in 2014. The patent record does not establish a current Paragraph IV dispute, active infringement action, or settlement involving this patent. A company-specific litigation conclusion should not be inferred from the patent alone because litigation is product- and defendant-specific.

No biosimilar pathway applies. Transdermal products containing conventional small-molecule active ingredients proceed through the abbreviated new drug application or other small-molecule FDA pathways, not the biosimilar pathway under the Public Health Service Act. [3][4]

What licensing deals involve the patent?

The patent record identifies the technology owner and patent family but does not itself establish a commercial license, royalty arrangement, assignment deal, or settlement agreement. Any licensing analysis must distinguish:

Assignment of the patent;
License of the transdermal platform;
License of a specific drug product;
Development agreement;
Settlement license in patent litigation.

The existence of the patent does not prove that a marketed patch product licensed it.

How does this patent compare with later transdermal patent estates?

U.S. Patent 5,676,968 is an early platform patent focused on matrix composition and crystallization control. Later transdermal estates commonly use a more layered strategy:

Patent category	Typical protected subject matter	Status relative to 5,676,968
Platform patch patents	General matrix, backing, liner, and adhesive architecture	Similar technical scope
Drug-specific formulation patents	One active ingredient with defined excipients	More product-specific
Method-of-use patents	Treatment indication, dose, or patient population	Separate legal category
Manufacturing patents	Coating, drying, laminating, die-cutting, or packaging	Process-focused
Device patents	Patch geometry, wear time, or application system	Physical-product focused
Release-profile patents	Flux, lag time, delivery rate, or duration	Performance-focused

For freedom-to-operate work, the expired patent should be screened out first. The relevant search should then focus on the active ingredient, formulation, patch brand, manufacturing process, and approved indication.

Key Takeaways

U.S. Patent 5,676,968 claims a transdermal adhesive-matrix system.
Claim 1 requires a water-impermeable top coating, active ingredient, adhesive matrix, skin-contact adhesive, and 0.1%-40% vinylpyrrolidone-vinyl acetate copolymer.
The copolymer is claimed as a crystallization inhibitor.
Dependent claims cover steroid and other drug classes, penetration enhancers, release liners, drug loading, backing materials, dimensions, and polyacrylate adhesives.
The patent issued on October 14, 1997.
Its ordinary U.S. term expired on October 14, 2014.
It is not a current U.S. patent barrier.
The patent does not create a current Paragraph IV or biosimilar risk.
Any present freedom-to-operate risk must come from later patents covering the active ingredient, product, formulation, use, manufacturing process, or device configuration.
The patent record alone does not establish a licensing deal, settlement, or active litigation.

FAQs

Does U.S. Patent 5,676,968 cover all transdermal patches?

No. It targets a specific adhesive-matrix configuration containing vinylpyrrolidone-vinyl acetate copolymer within the claimed concentration range.

Can a patch avoid the patent by using a reservoir system?

Historically, a properly designed reservoir system could avoid the requirement that the active ingredient be incorporated into the claimed adhesive matrix. The patent is now expired in any event.

Is a polyacrylate adhesive required by claim 1?

No. Polyacrylate is required only by dependent claim 10. Claim 1 requires a skin-contact adhesive but does not limit that adhesive to polyacrylate.

Does the patent cover scopolamine patches?

Claim 3 expressly lists scopolamine. A scopolamine patch would historically have required all limitations of claim 1, not merely the presence of scopolamine.

Can this expired patent be used to challenge a later transdermal patent?

Yes. The patent may remain relevant as prior art against later claims, subject to the applicable prior-art rules, claim construction, priority dates, and disclosure in the later patent.

References

United States Patent and Trademark Office. (1997). U.S. Patent No. 5,676,968, Transdermal therapeutic system. https://patents.google.com/patent/US5676968A/en
United States Code. (2023). 35 U.S.C. §§ 154 and 156: Patent term and patent term extension. https://uscode.house.gov/
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
U.S. Food and Drug Administration. (2023). Abbreviated new drug application process. https://www.fda.gov/drugs/types-applications/abbreviated-new-drug-application-anda-prescription-generic-drug-product-reviews

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	41 36 057.5	Oct 31, 1991
Germany	42 10 711.3	Mar 27, 1992

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	158181	⤷ Start Trial
Australia	1652997	⤷ Start Trial
Australia	2895392	⤷ Start Trial
Australia	712692	⤷ Start Trial
Canada	2120599	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,676,968

Summary for Patent: 5,676,968