United States Patent 4,783,337: Claim Scope, Expiration, and Osmotic Drug-Delivery Patent Landscape

U.S. Patent No. 4,783,337 is an Alza Corporation patent covering bilayer osmotic drug-delivery systems, commonly associated with the push-pull osmotic pump architecture. It claims a permeable or semipermeable wall, a drug-containing composition, a second expandable osmotic composition, and one or more delivery passageways. The patent issued on November 8, 1988, and its enforceable term expired in 2005 under the pre-Uruguay Round patent-term rule. It does not currently create a U.S. patent barrier for generic or branded products.

The claims are broad in therapeutic coverage but narrow in device architecture. A potentially infringing product would generally need to use the claimed two-composition osmotic arrangement, with fluid entering through the wall and the second composition assisting delivery of the drug formulation through a passageway.

What does U.S. Patent 4,783,337 cover?

The patent covers controlled-release osmotic dosage forms in which two internal compositions cooperate to deliver a drug over time.

The core technical elements are:

A shaped wall that admits external fluid.
A compartment inside the wall.
A first composition containing the drug and an osmopolymer.
A second composition containing an osmopolymer, with or without an osmagent.
One or more passageways through the wall.
Fluid absorption by the internal compositions.
Expansion or hydration of the second composition to push or assist delivery of the first composition.

The claims extend across oral, gastrointestinal, rectal, and vaginal delivery environments. The specification and claims also identify numerous drug classes, including ACE inhibitors, calcium-channel blockers, histamine receptor antagonists, cardiovascular drugs, nonsteroidal anti-inflammatory drugs, polypeptides, and other therapeutics.

The patent is principally a drug-delivery-system patent, not a patent directed to the chemical composition of an active pharmaceutical ingredient.

When did U.S. Patent 4,783,337 expire?

U.S. Patent 4,783,337 expired on November 8, 2005, based on the 17-year term applicable to patents issuing from applications filed before June 8, 1995. The patent therefore has no remaining enforceable U.S. patent term. [1][2]

Event	Date
U.S. patent issued	November 8, 1988
Applicable term rule	17 years from issue
Patent expiration	November 8, 2005
Current enforceability	Expired
Current U.S. exclusivity value	None as an enforceable patent right

The expiration analysis concerns the patent itself. It does not establish that every product using an osmotic pump is free from later patent rights. Later patents may cover specific pump geometries, membranes, formulations, manufacturing processes, release profiles, or commercial products.

What are the independent claims in U.S. Patent 4,783,337?

The patent contains 79 claims. The independent claims create several overlapping claim groups.

Claim	Principal subject matter	Scope
1	Osmotic device for ACE inhibitors	Two compositions, osmotic wall, passageway
3	Method of administering an ACE inhibitor	Oral administration using the two-composition device
4	Osmotic device for calcium antagonists	Drug composition plus osmotic second composition
5	Method of managing calcium-channel-blocker plasma levels	Oral controlled delivery
6	Dosage form for histamine receptor blockers	Two-composition osmotic device
9	General beneficial-agent osmotic device	Broadest central device formulation
29	Controlled delivery to a biological environment	Drug composition and cooperating osmotic composition
48	Controlled delivery of a drug formulation	Drug, solute, polymer, and cooperating formulation
62	Dosage form for controlled drug delivery	Drug formulation plus osmotically effective composition
65	Osmotic device with drug formulation and osmotic composition	Semipermeable wall and delivery passageway
66	Composition for forming a drug-delivery system	Laminar first and second compositions
67	Method of gastrointestinal administration	Oral administration using two different osmotic compositions
76	Diltiazem osmotic device	Drug-specific device claim
78	Nicardipine osmotic device	Drug-specific device claim

Claims 2, 7, 8, 10-28, 30-46, 49-61, 63-64, 68-75, 77, and 79 depend on these independent claims.

How broad is claim 9?

Claim 9 is the principal generic device claim. It does not limit the beneficial agent to a particular therapeutic class. Instead, it requires:

A wall that is at least partly semipermeable.
A wall substantially impermeable to the beneficial agent.
A compartment.
A first drug-delivery means containing the drug and an osmopolymer.
A second assisting means containing an osmopolymer.
A passageway connecting the first means with the exterior.

The claim uses functional language, including "first means for delivering" and "second means for assisting." Under U.S. claim-construction principles, the scope of a means-plus-function limitation may be tied to corresponding structures disclosed in the specification and their equivalents under 35 U.S.C. §112(f). The practical scope is therefore not unlimited merely because the claim uses broad functional terminology. [3]

A competing product would face a claim 9 issue if it uses a classic push-pull architecture in which:

The drug layer hydrates and becomes dispensable.
A separate push layer hydrates and expands.
The wall controls water ingress.
The drug exits through a drilled, molded, porous, or otherwise defined passageway.

A product using a single drug-containing osmotic core without a separate assisting osmotic layer would have a stronger non-infringement position against the two-composition limitation, although other patent claims could remain relevant.

What formulations and device structures are protected?

The dependent claims add material limitations concerning membranes, layers, osmotic agents, passageways, drug identity, and route of administration.

Wall and membrane limitations

Claims 10, 33, 35, 36, 37, 45, and 46 cover or narrow the wall structure. The recited materials include:

Cellulose acylate
Cellulose diacylate
Cellulose triacylate
Cellulose acetate
Cellulose diacetate
Cellulose triacetate
Cellulose acetate butyrate
Cellulose acetate propionate
Cellulose ester and ether materials

Claim 36 covers a laminate having a semipermeable lamina and a microporous lamina. Claims 32 and 33 address pores formed by leaching a removable material or present as micropores in a cellulose-acylate wall.

These limitations are important because the membrane controls water influx, internal pressure, hydration rate, and drug-release kinetics.

Bilayer and osmotic-composition limitations

Claims 11 and 12 require the first and second means to be arranged as layers and to imbibe fluid through the wall. Claims 13 and 34 further specify relative osmopolymer molecular weight or fluid uptake by both internal compositions.

Claims 40-42 add functional or compositional requirements:

The drug layer forms a dispensable drug-containing formulation.
The assisting layer forms an in situ formulation.
The polymer in either composition may be water soluble.

Claim 66 is directed to the pre-device composition itself. It requires a laminar arrangement in which:

Composition 1 contains drug and osmopolymer.
Composition 2 contains osmagent and osmopolymer.
Both compositions exhibit an osmotic pressure gradient across a semipermeable film.

This claim could be relevant to intermediate products, bilayer tablets, or manufacturing-stage assemblies, subject to proof that the accused composition has the claimed structure and properties.

Passageway limitations

Claims 26-28, 31-33, and 45-46 narrow the outlet structure. They cover:

Multiple passageways.
Microporous members.
One or more pores.
Leached pores.
Micropores in cellulose-acylate walls.
A passageway communicating with the drug-containing composition.

A delivery opening located only in the push layer, or an outlet that does not communicate with the drug composition, could avoid particular claim limitations. The physical location of the outlet is therefore a central infringement question.

Which drugs are expressly identified in the claims?

The claims identify drug classes and specific active ingredients. These references do not create active composition-of-matter rights in the drugs. They limit the device claims only where the relevant dependent claim is asserted.

Drug category	Examples in the claims
ACE inhibitors	Lisinopril, ramipril, enalapril, captopril, enalaprilat
Histamine receptor blockers	Famotidine, cimetidine, ranitidine, nizatidine, sucralfate, etintidine
Calcium-channel blockers	Verapamil, diltiazem, nicardipine, amlodipine and others
Other cardiovascular drugs	Milrinone, amrinone, digoxin, propranolol, atenolol
NSAIDs	Ibuprofen, ketoprofen, zomepirac, flurbiprofen, indomethacin
Other drugs	Theophylline, salbutamol, diazepam, furosemide, hydrochlorothiazide, haloperidol, danazol, cephalexin, erythromycin

The wording supplied by the user contains typographical errors, including "famatidine," "propanolol," "mimodipine," "flurobiprofen," and "captompril." The issued patent should control for legal analysis. Patent databases and the official file history are the proper sources for the authoritative claim text. [1][2]

What is the patent landscape around Alza osmotic pump technology?

U.S. Patent 4,783,337 belongs to a larger Alza osmotic-delivery patent cluster. The relevant landscape generally includes four patent groups.

Early osmotic pump patents

Earlier Alza patents established foundational osmotic devices with semipermeable walls, osmotic pressure, and delivery passageways. These patents may cover single-layer osmotic systems, membrane technology, and general controlled-release principles.

Push-pull and bilayer patents

The 4,783,337 patent is directed to a two-composition architecture. Related patents in this field may claim:

Specific push-layer compositions.
Drug-layer formulations.
Bilayer tablet manufacture.
Membrane coating techniques.
Passageway drilling.
Controlled release of poorly soluble or highly soluble drugs.
Geometry and dimensional relationships.
Use of expandable driving layers.

Later patents may have had longer terms than the 4,783,337 patent and could have provided the operative protection for commercial products using similar systems.

Drug-specific osmotic products

Separate patents may protect commercial formulations of specific drugs such as methylphenidate, oxybutynin, glipizide, nifedipine, or other agents. Those patents can cover release profiles, dose strength, pharmacokinetics, clinical use, or formulation details without depending on the expired 4,783,337 patent.

Manufacturing and coating patents

A product can face patent risk from manufacturing patents even when the basic dosage-form patent has expired. Relevant processes may include:

Bilayer compression.
Core encapsulation.
Semipermeable coating.
Laser drilling.
Pore formation by leaching.
Membrane plasticization.
In-process testing of release rate.
Coating thickness control.

A freedom-to-operate review must therefore examine later patent families, continuations, divisionals, foreign counterparts, and terminal disclaimers rather than relying on the status of U.S. Patent 4,783,337 alone.

Was U.S. Patent 4,783,337 listed in the Orange Book?

U.S. Patent 4,783,337 is not a current Orange Book barrier. The Orange Book lists patents and exclusivity associated with approved drug products, not every drug-delivery patent issued in the United States. [4]

A formulation or delivery-system patent can be Orange Book-listed if it is submitted by the NDA holder and meets FDA listing requirements. The mere fact that a patent claims an oral dosage form does not establish that it was listed for a particular NDA.

Because this patent expired in 2005, it cannot support a current Paragraph IV infringement dispute or block an ANDA launch.

What Paragraph IV and generic-entry risks existed?

During the patent’s term, an ANDA applicant seeking approval of a product potentially covered by the patent could have used a Paragraph IV certification if the patent was listed for the relevant reference product. A Paragraph IV certification asserts that the patent is invalid, unenforceable, or not infringed under 21 U.S.C. §355(j)(2)(A)(vii)(IV). [5]

The patent’s practical generic-entry risks were:

Risk category	Relevance to Patent 4,783,337
Direct device infringement	Material during the patent term
Paragraph IV certification	Possible only if properly listed for the relevant NDA
Method-of-use certification	Limited, because the patent primarily claims device and administration methods
Composition-of-matter challenge	Not applicable to the active ingredients themselves
Formulation design-around	Potentially significant
Post-expiration launch	No remaining patent obstacle from this patent
Biosimilar challenge	Not applicable

A generic manufacturer could design around the patent by using a non-osmotic controlled-release system, a single-compartment system, a different driving mechanism, a conventional matrix, a reservoir system, or a delivery architecture without the claimed cooperating osmopolymer composition.

Does the patent create biosimilar risk?

No. Biosimilars are regulated under the biologics pathway in section 351(k) of the Public Health Service Act. U.S. Patent 4,783,337 is directed to drug-delivery devices and includes certain polypeptides as possible beneficial agents, but it is not a biologic composition patent and has expired. [6]

The patent could have been technically relevant to a delivery device for a peptide or protein, but it would not establish exclusivity over the biologic itself, its amino-acid sequence, cell line, manufacturing process, or formulation unless those features were separately claimed.

How strong was the patent estate?

The patent was technically important but legally narrow in several respects.

Strengths

The claims cover the central two-layer push-pull architecture.
The claims use broad beneficial-agent language.
The patent includes device, method, composition, route-of-administration, and drug-specific claims.
Dependent claims cover multiple membrane and pore configurations.
The claims reach both the drug layer and the cooperating osmotic layer.
Functional delivery language links the device structure to controlled release.

Weaknesses

The patent requires two internal compositions or means.
The wall must admit fluid while limiting drug passage.
The passageway must communicate with the drug-containing composition in several claims.
The claims are vulnerable to prior-art attacks involving earlier osmotic pumps and bilayer systems.
Means-plus-function construction may limit claim 9 to disclosed structures and equivalents.
The patent’s term ended in 2005.
Later patents could supersede its commercial importance even where they use similar technology.

The patent’s present legal strength is zero because an expired patent cannot be enforced. Its historical technical value remains relevant for prior-art analysis, patent-family mapping, and interpretation of later Alza and osmotic-pump patents.

What patent litigation affects U.S. Patent 4,783,337?

The patent has no current litigation value because it is expired. Historical litigation involving osmotic dosage forms has generally focused on later, product-specific, or continuation patents rather than relying on an expired foundational patent as a present injunction basis.

The most relevant litigation questions for a product review are:

Whether a later patent claims the same bilayer pump more narrowly.
Whether the commercial product has an Orange Book-listed delivery-system patent.
Whether the patent family contains continuations with later expiration dates.
Whether a settlement agreement delayed generic entry under a later patent.
Whether the accused product uses a materially different release mechanism.

An expired patent may still appear in litigation as prior art, a prosecution-history reference, a claim-construction aid, or part of a patent-family narrative. It cannot independently support an infringement action after expiration.

How does this patent compare with later osmotic delivery patents?

Issue	U.S. 4,783,337	Later osmotic-pump patents
Primary focus	General two-composition osmotic device	Often product, formulation, process, or release-profile specific
Drug coverage	Broad classes and named drugs	Usually one active ingredient or product
Device architecture	Drug layer plus assisting osmotic layer	May claim more precise geometry or materials
Membrane claims	Cellulose-based and microporous options	May claim newer coatings and pore-forming methods
Commercial enforceability	Expired in 2005	Depends on individual patent term
Orange Book relevance	Not currently operative	Potentially material if listed for an NDA
Generic risk	None from this patent	Can remain material under later patents
Biosimilar relevance	None	Depends on biologic-specific patents

What generic launch scenarios remain possible?

A generic or follow-on manufacturer would not need to overcome U.S. Patent 4,783,337 today. The relevant launch analysis would focus on later rights and regulatory requirements.

Potential design strategies include:

A monolithic matrix tablet.
A conventional coated reservoir system.
A single-layer osmotic tablet.
An osmotic system using a non-polymeric osmagent.
A system in which the driving layer does not comprise the claimed osmopolymer.
A dosage form with a different outlet arrangement.
A liquid, suspension, multiparticulate, or capsule-based controlled-release system.
A formulation using a different membrane or pore-generation process.

The commercial question is whether the alternative delivers equivalent pharmacokinetics, stability, manufacturability, dose loading, and patient adherence. The patent itself does not prevent any of these approaches.

Does the patent have geographic coverage outside the United States?

U.S. Patent 4,783,337 provided rights only in the United States. Foreign counterparts, if filed, would have had separate prosecution histories, claim scope, term calculations, and legal status. A U.S. expiration date does not establish the status of corresponding patents in Europe, Japan, Canada, Australia, or other jurisdictions.

For international freedom-to-operate work, the relevant analysis must distinguish:

Priority applications.
PCT filings.
National-phase patents.
Continuations and divisionals.
Patent-term adjustments or extensions.
Abandoned applications.
National revocations or oppositions.
Foreign term rules.

No foreign patent can be treated as active solely because it is related to U.S. Patent 4,783,337.

Key Takeaways

U.S. Patent 4,783,337 covers a bilayer or two-composition osmotic drug-delivery device.
Its central architecture has a semipermeable wall, drug layer, expandable osmotic layer, and delivery passageway.
Claim 9 is the broadest central device claim, while claims 29, 48, 62, and 65 provide overlapping general device coverage.
Claims 1, 3, 4, 5, 6, 67, 76, and 78 target specific therapeutic classes, administration methods, or drugs.
The patent expired on November 8, 2005.
It cannot currently support a Paragraph IV litigation strategy, injunction, royalty demand, or launch block.
It is not a biologic patent and creates no biosimilar exclusivity.
It is not a current Orange Book barrier.
Later Alza or third-party patents may still cover particular osmotic products, formulations, membranes, manufacturing processes, or release profiles.
Current freedom-to-operate analysis must focus on unexpired continuation, divisional, improvement, product-specific, and manufacturing patents.

Frequently Asked Questions

Can an ANDA applicant launch a product that uses the same push-pull osmotic concept?

Yes, U.S. Patent 4,783,337 itself expired in 2005. The applicant must still review later unexpired patents covering the specific product, formulation, manufacturing process, or release profile.

Does claim 24 patent lisinopril, ramipril, enalapril, or captopril?

No. Claim 24 limits a device claim to an identified ACE inhibitor. It does not claim the active pharmaceutical ingredient as a chemical compound.

Could a single-layer osmotic tablet infringe this patent?

It would have a stronger non-infringement position because many claims require a first drug-containing composition and a second osmotic composition. The answer would depend on whether the single-layer system nevertheless contains equivalent claimed structures under the applicable claim construction.

Are the diltiazem and nicardipine claims still enforceable?

No. Claims 76-79 are subject to the patent’s expiration in 2005 and are no longer enforceable in the United States.

Is the patent relevant to OROS products?

Yes, technically and historically. The claims describe core elements associated with push-pull osmotic delivery. They do not, however, establish that every OROS product is covered, and the patent itself is no longer enforceable.

References

United States Patent and Trademark Office. (1988). U.S. Patent No. 4,783,337, Osmotic device for delivering a beneficial agent. U.S. Department of Commerce.
Google Patents. (n.d.). US4783337A: Osmotic device for delivering a beneficial agent. Google. https://patents.google.com/
United States Code, 35 U.S.C. §112(f).
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations, 43rd edition. FDA.
Federal Food, Drug, and Cosmetic Act, 21 U.S.C. §355(j)(2)(A)(vii)(IV).
Public Health Service Act, 42 U.S.C. §262(k).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	394944	⤷ Start Trial
Austria	397180	⤷ Start Trial
Austria	A150789	⤷ Start Trial
Austria	A88084	⤷ Start Trial
Australia	2251183	⤷ Start Trial
Australia	566110	⤷ Start Trial
Belgium	898819	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,783,337

Summary for Patent: 4,783,337