United States Drug Patent 5,190,765: Claim Scope, Expiration, and Patent Landscape

U.S. Patent No. 5,190,765 covers a delayed-delivery osmotic dosage form using three coordinated polymer systems: a drug-layer polymer, a semipermeable wall containing a second cellulose polymer, and a hydroxyalkylcellulose subcoat. The claims target calcium-channel blockers, including verapamil, and extend to specified angiotensin-converting enzyme inhibitors.

The patent issued on February 16, 1993. Because the application predates the modern 20-year-from-earliest-effective-filing-date term, its ordinary U.S. term was 17 years from issuance, placing expiration in February 2010, subject to any terminal disclaimer or patent-term adjustment shown in the official file. The patent therefore does not present a current U.S. infringement barrier. Its technical disclosures remain relevant as prior art against later patent applications. (U.S. Patent No. 5,190,765, 1993; USPTO, 2024a)

What technology does U.S. Patent 5,190,765 protect?

The patent protects a delayed-delivery dosage form that uses osmotic pressure to expel drug through an exit opening after a programmed delay.

The claimed architecture has six required elements:

Claim element	Technical requirement
Drug composition	Contains 0.05 ng to 1.5 g of a calcium-channel blocker or specified substitute drug
Drug-layer polymer	Has molecular weight up to 1,000,000 and changes from a non-dispensable to a dispensable phase upon hydration
Push composition	Imbibes fluid, expands, and pushes the drug composition out of the dosage form
Outer wall	Contains a semipermeable cellulose polymer and 15 wt% to 85 wt% of a different cellulose polymer
Subcoat	Contains hydroxyalkylcellulose with molecular weight from 8,500 to 4,000,000
Delivery profile	Provides a 30-minute to seven-hour delay through the combined operation of the three polymer systems

The claim is directed to a dosage form, not to the active pharmaceutical ingredient as a molecule. It does not claim verapamil, nifedipine, or the other named drugs in isolation.

The core invention is the interaction between:

Fluid entering through the semipermeable wall.
Hydration and liquefaction of the drug composition.
Expansion of the push layer.
Controlled fluid passage through the wall.
Delayed activation created by the hydroxyalkylcellulose subcoat.
Expulsion of drug through one or more exit openings.

This combination is characteristic of an osmotic-controlled oral delivery system associated with Alza Corporation's OROS technology.

How broad is independent claim 1?

Independent claim 1 is structurally broad but technically constrained. It uses "comprising," which generally permits additional ingredients, layers, excipients, coatings, or manufacturing features so long as the accused dosage form includes every required claimed element.

The principal limitations are cumulative. A product would generally need to show all of the following to fall within the literal scope:

A drug composition with the specified dose range.
A polymer in that drug composition with the stated hydration behavior.
A separate expanding push composition.
A wall surrounding both compositions.
A semipermeable cellulose polymer in the wall.
A different cellulose polymer present at 15 wt% to 85 wt%.
A hydroxyalkylcellulose subcoat between the inner wall surface and the drug and push compositions.
At least one drug-delivery exit.
A 30-minute to seven-hour delay attributable to the combined polymer operation.

The most commercially significant limitations are the wall composition and the subcoat. A conventional extended-release tablet, matrix tablet, enteric-coated tablet, multiparticulate capsule, or transdermal system would not ordinarily satisfy these limitations because those products lack the claimed push layer and osmotic wall arrangement.

What does “comprising” mean in claim 1?

“Comprising” makes the claim open-ended. An accused product may include additional polymers, coatings, drug layers, lubricants, colorants, membranes, or delivery openings. Those additions do not avoid the claim if all required elements remain present.

The open transition does not eliminate the need for the specific claimed architecture. A product that omits the subcoat, omits the push composition, or uses a wall without the specified cellulose-polymer relationship would have a substantial literal-infringement defense.

How important is the 30-minute to seven-hour delay limitation?

The delay limitation is a material functional limitation. The claim requires delayed delivery within a defined time range and attributes that delay to the combined operation of three polymer systems.

The limitation creates two potential proof issues:

Whether the product actually produces the required delay under the relevant test conditions.
Whether the delay results from the claimed drug-layer polymer, wall polymer, and subcoat operating together.

A product that produces a seven-hour delay through an enteric coating, pH-triggered layer, or separate programmable mechanism may not satisfy this limitation if the claimed polymer combination is not responsible for the delay.

What do dependent claims 2 through 6 add?

What does claim 2 protect?

Claim 2 narrows claim 1 to:

Hydroxyethylcellulose as the subcoat polymer; and
Verapamil as the calcium-channel blocker.

This is the most commercially focused claim in the set. It directly targets an osmotic delayed-delivery verapamil dosage form using hydroxyethylcellulose in the subcoat.

The claim does not require a particular verapamil salt unless that limitation appears in the specification or prosecution history. A pharmaceutically acceptable salt or derivative could be covered if it falls within the claim construction of the underlying drug limitation.

What does claim 3 protect?

Claim 3 recites a calcium-channel blocker and its pharmaceutically acceptable derivatives. It appears to reinforce the drug-class limitation rather than add a major structural feature.

The claim's scope depends on how "derivatives" is construed. A derivative must remain sufficiently related to the claimed drug class and be pharmaceutically acceptable. The term would not automatically cover every cardiovascular drug with a calcium-modulating effect.

What does claim 4 protect?

Claim 4 lists specific calcium-channel blockers:

Nifedipine
Nilvadipine
Flunarizine
Nimodipine
Diltiazem
Nicardipine
Nitredipine
Nisoldipine
Felodipine
Amlodipine
Cinnarizine
Fendiline

The claim is a Markush-style species list. It narrows the drug identity but retains all structural limitations inherited from claim 1.

The list includes drugs with materially different pharmacology and formulation characteristics. A marketed product containing one of these ingredients would not be covered merely because it uses delayed release. It would also need the osmotic push-pull architecture, cellulose wall composition, hydroxyalkylcellulose subcoat, and claimed delay.

What does claim 5 protect?

Claim 5 replaces the calcium-channel blocker with an angiotensin-converting enzyme inhibitor or one of the listed compounds, including:

Ramipril
Fosinopril
Benazepril
Cilazapril
Perindopril
Zofenopril
Enalapril
Lisinopril
Captopril
Quinapril

The claim is unusual because it depends on a claim framed around a calcium-channel blocker but attempts to substitute a different therapeutic class. Its legal effect would depend on the prosecution history and the court's treatment of the dependency language.

A court could construe claim 5 as incorporating the dosage-form limitations of claim 1 while replacing the active ingredient limitation. It could also view the wording as internally inconsistent or as requiring correction under applicable claim-construction principles. The claim does not independently claim an ACE inhibitor formulation without the claim 1 architecture.

What does claim 6 protect?

Claim 6 covers an external immediate-release dose in contact with the wall. This is commonly associated with a loading dose or immediate-release overcoat, followed by delayed delivery from the osmotic core.

The external dose may create an initial pharmacokinetic pulse before the delayed internal dose is released. The claim requires contact with the wall, which is narrower than merely administering an immediate-release dose separately.

What patents protect the same osmotic delayed-delivery concept?

The relevant patent landscape has several overlapping technology groups.

Technology group	Typical protected subject matter	Relevance to U.S. Patent 5,190,765
Osmotic push-pull tablets	Semipermeable membrane, expandable push layer, drug layer, exit orifice	Directly overlaps the claimed architecture
Delayed-start osmotic systems	Subcoats, swelling layers, soluble barriers, delayed activation	Directly overlaps the 30-minute to seven-hour delay
Cellulose membrane systems	Cellulose acetate or related semipermeable polymers	Directly relevant to the wall limitation
Hydroxyalkylcellulose barriers	Hydroxyethylcellulose, hydroxypropylcellulose, and related coatings	Directly relevant to the subcoat limitation
Drug-layer rheology systems	Hydrating polymers that convert a solid or non-dispensable phase into an injectable or dispensable phase	Directly relevant to the drug-composition limitation
Immediate-release overcoats	External loading doses applied to the dosage-form wall	Relevant to claim 6
Manufacturing methods	Drilling, coating, bilayer compression, membrane control, and osmotic-core assembly	Potentially relevant to later patents but not expressly claimed here
Product-specific formulations	Verapamil, nifedipine, or ACE-inhibitor dosage forms	Relevant if they use the claimed structure

The patent should be analyzed as one historical member of the broader OROS and controlled-release dosage-form families. Later patents may claim different membrane compositions, laser-drilled openings, multilayer cores, dose dumping controls, manufacturing processes, or specific pharmacokinetic profiles.

When did U.S. Patent 5,190,765 lose exclusivity?

The patent issued on February 16, 1993. For a pre-June 8, 1995 U.S. application, the governing patent term was generally 17 years from issuance rather than 20 years from the earliest effective filing date. On that basis, the ordinary expiration date was February 16, 2010. (35 U.S.C. § 154; USPTO, 2024a)

Event	Date or period
Patent issuance	February 16, 1993
Ordinary 17-year patent term	February 16, 2010
Current status	Expired
Current enforceability	No prospective infringement exclusion based solely on this patent

A terminal disclaimer, reexamination certificate, patent-term adjustment, or other file-specific event could modify the exact legal record. The operative status should be confirmed in the USPTO Patent Center and the patent's maintenance records.

Because the patent is expired, a company does not need a license to practice the expired claims in the United States. A license may still be relevant for later continuation patents, foreign counterparts, know-how, trademarks, or separate manufacturing rights.

What is the Orange Book status of U.S. Patent 5,190,765?

U.S. Patent 5,190,765 is not itself an FDA approval or an Orange Book listing. The FDA Orange Book lists patents associated with specific approved drug products and approved uses. A broad formulation patent can be listed against a product only if the statutory and FDA listing requirements are satisfied. (FDA, 2024)

The patent's named drugs include verapamil, nifedipine, diltiazem, nicardipine, amlodipine, and several ACE inhibitors. That list does not establish that the patent was listed for every product containing those ingredients.

For an Orange Book analysis, the relevant questions are product-specific:

Whether the approved product used the claimed dosage form.
Whether the patent owner submitted the patent for listing.
Whether the patent covered the approved formulation or method of use.
Whether the listing remained active during the relevant abbreviated new drug application period.
Whether the patent had expired or been delisted.

An expired patent would not create a current Orange Book barrier to generic approval, even if it had previously been listed.

Were Paragraph IV challenges available against this patent?

Paragraph IV certifications are used in abbreviated new drug applications to challenge listed patents that are unexpired or to assert that a product will not infringe them. A patent that expired in 2010 cannot create a current 30-month stay or prospective Paragraph IV litigation risk based solely on that patent. (21 U.S.C. § 355; FDA, 2024)

Historically, a generic applicant could have challenged the patent by asserting that:

The dosage form did not contain the required subcoat.
The wall did not contain the specified cellulose polymer concentration.
The dosage form did not include a push composition.
The claimed delay was outside the 30-minute to seven-hour range.
The polymer did not undergo the claimed hydration-phase transition.
The claim was invalid for anticipation or obviousness.
The claim language was indefinite or internally inconsistent.

No current generic entrant needs to overcome this patent as a live exclusivity right. The commercial issue is whether later, unexpired patents cover the specific approved product.

How strong is the patent estate for a product using this technology?

The patent's current blocking strength is zero because the patent has expired. Its historical claim strength was mixed.

Strengths

The claim combines multiple structural elements.
The wall, push layer, subcoat, and delay profile create a detailed formulation fingerprint.
Claim 2 directly targets verapamil with hydroxyethylcellulose.
The open "comprising" language permits additional formulation components.
The claim reaches several therapeutic classes and named active ingredients.

Weaknesses

The claim requires a complex combination that may be difficult to prove in an accused product.
The delay limitation introduces testing and causation questions.
The polymer molecular-weight ranges may limit the claim in practice.
The specified cellulose wall composition creates design-around opportunities.
Claim 5 has potentially problematic dependency and drug-class substitution language.
The patent expired in 2010.

For historical litigation, the strongest infringement case would have involved a product with a bilayer osmotic core, cellulose-based semipermeable wall, hydroxyethylcellulose subcoat, and delayed verapamil delivery. A conventional matrix formulation would present a materially weaker case.

What generic launch scenarios exist today?

For products relying only on U.S. Patent 5,190,765, generic launch is not blocked by this patent.

The practical scenarios are:

Scenario	Patent effect
Conventional immediate-release generic	No meaningful relevance
Conventional extended-release matrix generic	Usually outside the structural claim scope
Osmotic generic with no hydroxyalkylcellulose subcoat	Potentially avoids a key limitation
Osmotic generic using a different wall polymer system	Potential design-around
Verapamil osmotic generic with the claimed three-polymer architecture	Historically high overlap, but no current patent barrier from this patent
Product covered by later patents	Must be analyzed separately
Foreign launch	Depends on national counterparts and their expiration status

What geographic coverage and manufacturing barriers matter?

The U.S. patent affected only U.S. conduct. Foreign counterparts, if granted, had separate terms, claim scope, prosecution histories, and expiration dates. A company conducting formulation, manufacture, importation, or sale in Europe, Japan, Canada, or other jurisdictions requires a country-by-country review.

Manufacturing barriers may remain even after patent expiration. The technology can require:

Bilayer or multilayer tablet compression.
Controlled membrane coating.
Precise wall thickness.
Controlled drilling or formation of exit openings.
Subcoat application between the core and the semipermeable wall.
Verification of osmotic pumping and delayed activation.
Stability testing for membrane permeability and dose delivery.

These are technical and regulatory barriers, not continuing rights under the expired patent.

What litigation and licensing conclusions follow?

The supplied claim set does not establish a current lawsuit, settlement, license, or Orange Book dispute. The patent's expiration removes it as a current U.S. exclusion right.

Any present diligence should focus on:

Continuations and divisionals in the same patent family.
Later patents assigned to Alza, Johnson & Johnson, or other controlled-release developers.
Product-specific patents for verapamil, nifedipine, and other listed drugs.
Formulation, manufacturing, and pharmacokinetic patents that issued after 1993.
Foreign family members with different expiration dates.
Trade-secret manufacturing knowledge and regulatory exclusivity.

The expired patent remains relevant as a prior-art reference. A later applicant cannot ordinarily obtain valid claims that merely restate the disclosed combination without a patentable distinction.

Key Takeaways

U.S. Patent 5,190,765 covers a delayed-delivery osmotic dosage form, not the claimed active ingredients as standalone compounds.
The central claim requires a drug layer, expanding push layer, semipermeable cellulose wall, hydroxyalkylcellulose subcoat, exit opening, and 30-minute to seven-hour delay.
Claim 2 specifically targets verapamil with a hydroxyethylcellulose subcoat.
Claim 5 attempts to extend the dosage-form concept to specified ACE inhibitors but has potentially problematic dependency language.
The patent issued February 16, 1993, and its ordinary U.S. term ended February 16, 2010.
The patent is not a current U.S. barrier to generic or competing formulation development.
Orange Book relevance is product-specific and cannot be inferred from the patent's drug list.
Current freedom-to-operate risk depends on later patents, foreign counterparts, regulatory exclusivities, and manufacturing know-how.

FAQs About U.S. Patent 5,190,765

Does U.S. Patent 5,190,765 cover all delayed-release verapamil products?

No. It covers products with the specified osmotic architecture and polymer combination. A matrix tablet, enteric-coated product, multiparticulate capsule, or different osmotic system may fall outside the claims.

Can a company manufacture the claimed dosage form in the United States today?

Yes, this patent does not currently block manufacture because its ordinary patent term expired in February 2010. Later patents and other intellectual-property rights require separate review.

Is hydroxyethylcellulose required for every claim?

No. Hydroxyethylcellulose is expressly required by claim 2. Claim 1 requires a hydroxyalkylcellulose subcoat, while the broader claim may cover other hydroxyalkylcellulose species within the stated molecular-weight range.

Does claim 6 require an immediate-release overcoat?

Claim 6 requires an external, instant dose of drug in contact with the dosage-form wall. The claim therefore targets a loading dose associated with the outside of the osmotic dosage form, although the exact coating structure depends on the specification and claim construction.

Are the listed ACE inhibitors protected as chemical compounds?

No. Claim 5 addresses dosage forms containing the listed ACE inhibitors. It does not claim the chemical compounds themselves, their synthesis, or every pharmaceutical formulation containing them.

References

Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.
Food and Drug Administration. (2024). Abbreviated new drug application regulations and patent certifications. U.S. Department of Health and Human Services.
United States Code. (2024). 21 U.S.C. § 355: New drugs.
United States Code. (2024). 35 U.S.C. § 154: Contents and term of patent; provisional rights.
United States Patent No. 5,190,765. (1993). Delayed delivery dosage form. United States Patent and Trademark Office.
United States Patent and Trademark Office. (2024a). Patent term calculator and patent term examination guidance. U.S. Department of Commerce.
United States Patent and Trademark Office. (2024b). Manual of Patent Examining Procedure, claim interpretation and dependency provisions. U.S. Department of Commerce.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	165000	⤷ Start Trial
Australia	2255092	⤷ Start Trial
Australia	654871	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,190,765

Summary for Patent: 5,190,765