US Patent 4,842,864: Scope, Claims, Expiration, and Transdermal Patch Patent Landscape

US Patent 4,842,864 covers a self-adhesive transdermal matrix built around four functional excipient classes: high-vinyl-acetate ethylene/vinyl acetate copolymer, a C12-C20 aliphatic monoalcohol, a cellulose derivative, and a polyhydric alcohol. The patent also covers steroid-loaded versions, particularly estradiol matrices, and a multistage high-temperature manufacturing process.

The patent issued on June 27, 1989. Because it predates the change to the 20-year filing-term regime, its ordinary US term was 17 years from issue and ended in 2006, absent an unusual term adjustment or extension. It is not a current US exclusionary barrier to generic or branded transdermal products. [1, 2]

What does US Patent 4,842,864 protect?

The patent protects a composition-defined transdermal matrix rather than a particular patch shape, backing layer, label, or therapeutic indication.

Its central technical combination is:

Component	Claimed range	Technical role
Ethylene/vinyl acetate copolymer	40-60 parts by weight	Matrix-forming polymer and adhesive phase
Higher aliphatic monoalcohol	40-60 parts by weight	Plasticizing, adhesive, and permeation-related phase
Cellulose derivative	1-20 parts by weight	Viscosity control, matrix stabilization, and release modulation
Polyhydric alcohol	0.1-8 parts by weight	Co-solvent, plasticizer, and permeation modifier
Active ingredient	0.01-10 parts by weight	Percutaneously delivered drug

The required balance is:

[ \frac{a+c}{b+d}=0.7\text{ to }1.3 ]

where:

(a) is the EVA quantity;
(b) is the higher aliphatic monoalcohol quantity;
(c) is the cellulose derivative quantity; and
(d) is the polyhydric alcohol quantity.

This ratio is a material limitation. A formulation that satisfies each individual ingredient range but falls outside the ratio is outside the literal scope of claims 1 and 2.

How are the independent claims structured?

Claim 1: Broad active-ingredient matrix

Claim 1 covers a self-adhesive matrix containing the specified excipient classes and any active ingredient capable of percutaneous administration.

The claim is compositionally broad because it does not restrict the active ingredient to steroids. It can potentially read on matrices containing hormones, analgesics, antiemetics, cardiovascular agents, or other transdermal drugs, provided all compositional and ratio limitations are met.

The phrase “comprises” generally makes the claim open-ended. A product may contain additional ingredients and still fall within the claim if it contains every required element in the claimed ranges.

Claim 2: Steroid matrix

Claim 2 is directed to a narrower active-ingredient category. It covers matrices containing:

estradiol;
progesterone;
testosterone;
derivatives of those compounds; or
corticosteroids.

Claim 2 is not limited to estradiol. A testosterone or progesterone formulation can fall within the claim if the excipient system and ratio requirements are satisfied.

Claim 12: Manufacturing process

Claim 12 covers a specific manufacturing sequence. Its key process limitations include:

Mixing EVA with part of the higher aliphatic monoalcohol at at least 110°C.
Incorporating the cellulose derivative at at least 110°C.
Adding the remainder of the monoalcohol at at least 110°C.
Homogenizing and allowing the mixture to stand for at least eight hours.
Heating to approximately 50-70°C.
Adding the polyhydric alcohol and active ingredient, generally in a solvent.
Homogenizing without heating.
Coating the mixture onto a temporary support at approximately 50-70°C and 100-300 g/m².
Heating at approximately 70-90°C to reduce residual solvent below 5% by weight.
Transferring the dried matrix to a final support.

A product can potentially avoid claim 12 while still implicating the composition claims. Conversely, a process that follows the claimed sequence may create process-claim exposure even if the final product is not marketed with every possible optional component.

What formulations are protected by claims 3 through 11?

Claims 3 through 11 narrow the generic composition through specific materials and concentration ranges.

Claim	Principal limitation
3	EVA containing 35-55% vinyl acetate
4	EVA containing approximately 45% vinyl acetate
5	Saturated or unsaturated C12-C20 monoalcohol
6	Alkyl or hydroxyalkyl cellulose
7	Listed cellulose derivatives, including ethyl cellulose and hydroxypropyl cellulose
8	Alkylene glycol or related glycol
9	Specific glycols, including ethylene glycol, propylene glycol, dipropylene glycol, polyethylene glycol, and polypropylene glycol
10	2-octyldodecan-1-ol, ethyl cellulose, dipropylene glycol, and estradiol
11	Approximately 45% EVA with 45% vinyl acetate, 2-octyldodecan-1-ol, ethyl cellulose, dipropylene glycol, and beta-estradiol

Claim 10: Estradiol formulation

Claim 10 identifies a particularly important embodiment:

EVA: 40-60 parts;
2-octyldodecan-1-ol: 40-60 parts;
ethyl cellulose: 1-20 parts;
dipropylene glycol: 0.1-8 parts; and
estradiol: 0.01-10 parts.

Because claim 10 depends on claim 1, the ratio requirement remains applicable.

Claim 11: Narrow beta-estradiol embodiment

Claim 11 narrows the formulation to approximately:

45 parts EVA;
40-45 parts 2-octyldodecan-1-ol;
5-10 parts ethyl cellulose;
1-5 parts dipropylene glycol; and
3-5 parts beta-estradiol.

The EVA must contain approximately 45% vinyl acetate, and the ethyl cellulose must have a viscosity of approximately 0.02-0.2 Pa·s.

The stated component ranges do not independently guarantee compliance with the ratio limitation inherited from claim 1. For example, a formulation with 45 parts EVA, 10 parts ethyl cellulose, 40 parts monoalcohol, and 1 part dipropylene glycol produces a ratio of:

[ \frac{45+10}{40+1}=1.34 ]

That formulation would fall outside the 0.7-1.3 ratio, despite satisfying the listed component ranges in claim 11. The dependent claim must be read with all limitations of the parent claim.

How strong is the patent estate for US Patent 4,842,864?

The patent had meaningful technical breadth when issued, but its present commercial strength is zero in the United States because the patent term ended in 2006.

Historical strengths

The patent combined several limitations that could have distinguished a conventional transdermal adhesive:

a relatively high-vinyl-acetate EVA polymer;
a long-chain monoalcohol;
cellulose-based rheology control;
a glycol component;
a defined balance between polymer/cellulose and alcohol/glycol phases; and
a defined thermal mixing and solvent-removal sequence.

The narrow estradiol claims could have been commercially important for matrix patches using the specified excipient platform.

Scope limitations

The claims are narrower than a general “transdermal patch” claim in several respects:

They require a self-adhesive matrix.
They require EVA within a defined weight range.
They require a higher aliphatic monoalcohol within a defined weight range.
They require a cellulose derivative.
They require a polyhydric alcohol.
They require the numerical ratio.
Claims 3-11 add specific chemical identities and concentration constraints.

A reservoir patch, hydrogel, silicone adhesive system, acrylic adhesive system, or polyurethane matrix would not fall within the literal composition claims merely because it delivers estradiol through the skin.

When did US Patent 4,842,864 lose exclusivity?

The patent issued June 27, 1989. Under the pre-1995 US patent term rule, the ordinary term was 17 years from issue, producing an expiration date of June 27, 2006. [1, 2]

Event	Date
US patent issued	June 27, 1989
Ordinary 17-year term	June 27, 2006
Current US enforceability	Expired
Current Paragraph IV relevance	None as an enforceable patent
Current biosimilar relevance	None

A patent expiration eliminates the right to exclude under the patent. It does not eliminate the technical value of the disclosure, formulation know-how, or manufacturing process.

What is the Orange Book status of US Patent 4,842,864?

US Patent 4,842,864 should not be treated as a currently effective Orange Book patent barrier.

Orange Book listing is tied to an approved drug product and the patent information submitted by the new drug application holder. The existence of a patent covering a formulation does not automatically make that patent an Orange Book-listed patent. FDA listing also does not extend an expired patent term. [3]

For transdermal estradiol products, relevant Orange Book patents would need to be reviewed at the product level, including products such as:

generic estradiol transdermal systems;
Climara;
Minivelle;
Vivelle-Dot;
Alora;
Estraderm; and
other approved estradiol delivery systems.

The key distinction is between the expired foundational matrix patent and later patents covering:

patch dimensions;
drug loading;
adhesive chemistry;
dose delivery;
crystallization control;
backing layers;
release liners;
manufacturing controls;
application schedules; and
specific therapeutic uses.

Are there current Paragraph IV challenges involving this patent?

No current Paragraph IV risk should attach to US Patent 4,842,864 because its US term expired in 2006.

Paragraph IV certifications are relevant when an ANDA applicant addresses an unexpired patent listed for an approved drug. An expired patent cannot block an ANDA launch, although other unexpired patents may remain relevant. [4]

Historical litigation or certification activity involving estradiol patches should not be attributed to this patent without a product-specific court docket or FDA patent listing. Later patents may have generated Paragraph IV disputes even where the underlying technology originated from the matrix architecture disclosed in US 4,842,864.

Does biosimilar risk apply to this patent?

No. Biosimilar law is not the relevant pathway for an estradiol transdermal patch.

Estradiol is a small molecule. Generic transdermal products generally proceed through the ANDA pathway under section 505(j), subject to product-specific bioequivalence, adhesion, pharmacokinetic, and quality requirements. The BPCIA biosimilar pathway under section 351(k) applies to biological products, not conventional estradiol patches. [5]

What manufacturing and intellectual-property barriers remain?

Although the patent is expired, technical barriers may remain in five areas.

Adhesion and skin performance

A successful patch must balance:

adhesion over the intended wear period;
acceptable peel and shear properties;
low residue;
limited irritation;
controlled drug release; and
reliable delivery across variable skin conditions.

Drug crystallization

Estradiol and related steroids can crystallize or partition unevenly in adhesive matrices. Later patents may target supersaturation, crystal inhibitors, drug loading, or storage stability.

Dose uniformity

A solvent-based coating and drying process must maintain uniform drug distribution across the web. Residual solvent, coating weight, drying temperature, and line speed can affect dose uniformity and release.

Component substitution

Replacing 2-octyldodecan-1-ol, ethyl cellulose, dipropylene glycol, or the specified EVA grade can change adhesion and release behavior. Such substitutions would generally avoid the literal claim only if the resulting composition falls outside every relevant claim.

Process scale-up

Claim 12 identifies process parameters that may have been important for laboratory manufacture. Commercial scale-up can create different risks involving mixing torque, thermal history, residence time, solvent removal, and coating uniformity.

How does this patent compare with later transdermal patch patent estates?

Estate type	Typical protected subject matter	Relevance of US 4,842,864
Foundational matrix patent	EVA, cellulose, glycol, monoalcohol, active ingredient	Directly relevant
Acrylic adhesive patent	Acrylic copolymer composition and drug release	Usually outside literal scope
Silicone adhesive patent	Silicone pressure-sensitive adhesive	Usually outside literal scope
Reservoir patch patent	Drug reservoir, membrane, backing, and adhesive	Different architecture
Estradiol use patent	Menopausal therapy, dosing, or treatment schedule	Separate method-of-use layer
Manufacturing patent	Coating, drying, lamination, or solvent control	Potentially related but distinct
Device patent	Patch geometry, backing, liner, or packaging	Separate device layer

The patent is therefore best characterized as an expired foundational formulation patent, not as a complete patent estate for modern estradiol transdermal products.

Which companies could have commercial exposure?

Historical and current commercial exposure would depend on whether a product used the claimed EVA-monoalcohol-cellulose-glycol matrix, not merely whether it delivered estradiol through the skin.

Relevant product developers and manufacturers in the estradiol patch market have included:

Novartis and Sandoz;
Bayer-related women’s health businesses;
3M;
Mylan and Viatris;
Teva;
Endo;
Amneal;
Watson and Actavis; and
other generic transdermal manufacturers.

The expired status of US 4,842,864 means those companies would generally face no current US infringement liability based solely on this patent. Commercial exposure may instead arise from later patents, FDA exclusivity, product-specific formulation patents, or manufacturing patents.

What generic launch scenarios exist?

Immediate technical freedom from this patent

A generic manufacturer does not need to design around US 4,842,864 after its expiration. It may use the disclosed formulation architecture, subject to other live patents and regulatory requirements.

Design-around strategy

A manufacturer can also avoid the claim architecture by using:

an acrylic adhesive;
a silicone adhesive;
a hydrogel;
a reservoir system;
a different plasticizer;
a different cellulose or polymer system; or
a composition outside the claimed ratio.

Regulatory launch risk

The principal current risks are likely to be:

product-specific Orange Book patents;
therapeutic equivalence or bioequivalence requirements;
adhesion performance;
manufacturing validation;
residual solvent limits;
supply of specialty polymers; and
litigation over later formulation or use patents.

Key Takeaways

US Patent 4,842,864 covers a self-adhesive EVA transdermal matrix with a C12-C20 monoalcohol, cellulose derivative, polyhydric alcohol, and active ingredient.
Claims 1 and 2 are the principal composition claims.
Claims 10 and 11 focus on estradiol, especially beta-estradiol, with 2-octyldodecan-1-ol, ethyl cellulose, dipropylene glycol, and approximately 45% vinyl acetate EVA.
Claim 12 covers a detailed high-temperature mixing, aging, solvent-addition, coating, and drying process.
The ratio ((a+c)/(b+d)) between 0.7 and 1.3 is a central limitation.
The US patent issued June 27, 1989, and its ordinary term ended June 27, 2006.
It is not a current US patent barrier, current Paragraph IV barrier, or biosimilar barrier.
Modern estradiol patch risk must be assessed against later product, formulation, method-of-use, manufacturing, and device patents.
The patent remains relevant as prior art and technical disclosure, but not as an enforceable US exclusion right.

FAQs

Can a generic estradiol patch use the exact formulation disclosed in US 4,842,864?

Yes, from this patent alone, because the US patent term expired in 2006. Other unexpired patents and FDA requirements may still apply.

Does using 45% vinyl acetate EVA automatically infringe the patent?

No. The product must satisfy all applicable limitations, including the specified monoalcohol, cellulose derivative, polyhydric alcohol, active ingredient, weight ranges, and ratio.

Is 2-octyldodecan-1-ol required for every claim?

No. It is expressly required by claim 10 and claim 11. The broader claims permit a higher aliphatic monoalcohol within the claimed category.

Can an acrylic estradiol patch infringe this patent?

A purely acrylic system would generally not satisfy the required EVA limitation. It could still implicate later patents directed to acrylic adhesive systems or estradiol delivery.

Does the patent cover the therapeutic use of estradiol for menopause?

No. The claims provided are directed to a matrix and a manufacturing method. They do not claim a menopausal treatment method, dosage regimen, or clinical indication.

References

United States Patent No. 4,842,864, “Self-adhesive matrix for the percutaneous administration of active ingredients,” issued June 27, 1989.
35 U.S.C. § 154, patent term provisions applicable to pre-June 8, 1995 applications.
U.S. Food and Drug Administration. Approved Drug Products with Therapeutic Equivalence Evaluations, commonly known as the Orange Book.
U.S. Food and Drug Administration. ANDA Submissions - Amendments and Reviews: Patent Certifications and Paragraph IV Certifications.
Biologics Price Competition and Innovation Act of 2009, Pub. L. No. 111-148, § 7002.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
France	87 04133	Mar 25, 1987

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	69724	⤷ Start Trial
Germany	3866408	⤷ Start Trial
European Patent Office	0288336	⤷ Start Trial
Spain	2027773	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 4,842,864