United States Drug Patent 4,612,008: Claim Scope, Expiration, and Osmotic Drug-Delivery Patent Landscape

U.S. Patent No. 4,612,008 covers a bilayer osmotic delivery system with a drug-containing composition and a separate delivery composition. The core architecture requires a semipermeable or partly microporous wall, an internal drug layer, an osmagent-polymer delivery layer, and an outlet passageway. The patent is expired and does not currently block generic, branded, or follow-on development in the United States.

What does U.S. Patent 4,612,008 protect?

The patent protects a controlled-release osmotic device in which two internal compositions generate osmotic driving force:

A first composition containing the beneficial agent or drug, an osmagent, and an osmopolymer.
A second composition containing an osmagent and an osmopolymer but no required drug.
A wall that admits external fluid while restricting drug passage.
A passageway connecting the drug composition to the external environment.
Fluid imbibition by both compositions to generate controlled drug delivery.

The claims are directed principally to device structure and operating mechanism. They are not limited to a particular active pharmaceutical ingredient, commercial product, dose, or disease indication except where narrower dependent claims specify a drug class or biological environment.

Core inventive concept

The central claimed arrangement is a two-layer osmotic core:

Element	Claimed requirement
Wall	Semipermeable, or in some claims partly microporous
Drug compartment	Drug, osmagent, and osmopolymer
Delivery compartment	Osmagent and osmopolymer
Internal arrangement	Separate compositions, commonly in laminar or layered form
Fluid source	External aqueous or biological fluid
Outlet	Passageway through the wall, either preformed or formed in use
Delivery mechanism	Both compositions imbibe fluid and generate pressure or expansion
Result	Controlled delivery over a prolonged period

The claims use functional language such as "exhibits an osmotic pressure gradient," "imbibes fluid," and "delivering ... at a controlled rate." Those limitations would require construction in light of the specification and prosecution history in an infringement dispute.

Which claims of U.S. Patent 4,612,008 are independent?

Claims 1, 7, 17, and 20 are the principal independent claims based on the supplied claim set.

Claim 1: Broad osmotic device claim

Claim 1 covers an osmotic device for delivering a beneficial agent to an environment of use. It requires:

A wall that is permeable to external fluid.
Substantial impermeability to the beneficial agent.
A compartment within the wall.
A first composition containing the beneficial agent, osmagent, and osmopolymer.
A second composition containing an osmagent and osmopolymer.
A passageway communicating with the first composition and the exterior.

Claim 1 is the broadest general device claim. It is not restricted to human administration, oral delivery, a pharmaceutical drug, or a particular wall material.

Claim 7: Biological drug-delivery device

Claim 7 narrows the subject matter to a beneficial drug delivered to a biological environment. It requires:

A shaped wall.
A drug-containing composition with a dosage amount of drug.
A second composition containing an osmotically effective compound and polymer.
A passageway connected to the drug composition.
Controlled delivery of a therapeutically effective amount over a prolonged period.

Compared with claim 1, claim 7 adds a biological environment, a drug dosage amount, and therapeutic delivery language.

Claim 17: Drug-formulation claim

Claim 17 requires a drug formulation and a separate delivery formulation. The drug formulation must contain:

A drug ranging from insoluble to very soluble in biological fluid.
An osmotically effective solute.
A polymer that imbibes and absorbs fluid.

The delivery formulation must contain:

An osmotically effective solute.
A fluid-imbibing and fluid-absorbing polymer.

This claim is more formulation-specific than claim 7. It focuses on the hydrated compositions formed during device operation.

Claim 20: Composition-of-matter claim

Claim 20 is directed to a composition useful for making a drug-delivery system. It requires:

A first composition containing drug, osmagent, and osmopolymer.
A second composition in laminar arrangement with the first.
An osmotic pressure gradient across a semipermeable polymeric film against aqueous or biological fluid.

This claim is potentially important in the supply chain because it is not framed solely as a finished delivery device. A layered core supplied for incorporation into an osmotic system could raise claim-scope questions if the other limitations are met.

How do the dependent claims narrow the patent?

Claims 2 through 6, 8 through 16, and 18 through 27 add materials, environments, formulations, and passageway structures.

Claims	Subject matter
2	Cellulose acylate, diacylate, triacylate, acetate, diacetate, or triacetate wall
3	Algicide, germicide, herbicide, fungicide, insecticide, or pesticide
4	First and second compositions arranged as layers
5	Both compositions imbibe external fluid
6	Second osmopolymer has higher molecular weight than first
8	Drug composition osmotic compound and polymer imbibe fluid
9	Delivery composition imbibes external fluid
10	Cellulose acylate, diacylate, or triacylate wall
11	Laminate containing semipermeable and microporous laminae
12	Drug formulation and in-situ delivery formulation
13	Drug-layer polymer is water soluble
14	Drug-layer polymer is cross-linked
15	Delivery-layer polymer is water soluble
16	Delivery-layer polymer is cross-linked
18	Human biological environment
19	Gastrointestinal tract and oral administration
21, 23, 26	Passageway forms in the environment of use
22, 24	Microporous wall with pore former removed during operation
25	Sorbitol is the pore former
27	Specific sugar or polyol pore formers

The dependent claims create multiple technical embodiments but do not extend the patent term. A product that avoids a dependent limitation may still fall within an independent claim.

What formulations are protected by U.S. Patent 4,612,008?

The claimed formulations are bilayer osmotic compositions rather than conventional matrix tablets.

Drug layer

The drug layer contains:

A beneficial drug or agent.
An osmagent or osmotically effective solute.
An osmopolymer or fluid-imbibing polymer.

The claims do not require a specific drug chemistry. Claim 3 covers nonhuman-use agents such as pesticides, while claims 7, 17, and 19 address therapeutic and oral drug delivery.

Delivery layer

The delivery layer contains:

An osmagent.
An osmopolymer or water-absorbing polymer.
No express requirement for drug.

The delivery layer hydrates after exposure to external fluid. Its role is to contribute osmotic pressure, swelling, expansion, or formulation formation that assists delivery of the drug-containing layer.

Layered arrangement

Claim 4 requires the first and second compositions to be present as layers. Claim 20 expressly requires a laminar arrangement. A device using a homogeneous blend rather than distinguishable drug and delivery regions would present a stronger non-infringement position against those narrower claims, although claim 1 and other broad claims would require separate analysis.

What wall materials and passageways are covered?

The patent claims both semipermeable and microporous wall technologies.

Semipermeable walls

Claims 2 and 10 identify cellulose-based materials, including:

Cellulose acetate.
Cellulose diacetate.
Cellulose triacetate.
Other cellulose acylates and diacylates.

These materials allow water or biological fluid to enter while limiting passage of the drug formulation.

Laminated walls

Claim 11 covers a wall comprising:

A semipermeable lamina; and
A microporous lamina.

This language captures composite membrane designs in which the transport properties are distributed across multiple wall layers.

In-situ passageways

Claims 21, 23, and 26 cover passageways formed in the environment of use rather than necessarily drilled or mechanically created before administration.

Pore-forming walls

Claims 22, 24, 25, and 27 address microporous compositions containing a pore former. The pore former is removed during operation, creating fluid pathways. The listed pore formers include:

Sorbitol.
Sucrose.
Glucose.
Fructose.
Mannitol.
Mannose.
Galactose.
Aldohexose.
Altrose.
Talose.
Lactose.

These claims are narrower than the independent claims because they require a pore-forming mechanism or specified pore-former chemistry.

When did U.S. Patent 4,612,008 lose exclusivity?

U.S. Patent 4,612,008 is expired. It issued in 1986, and patents from that period generally had a term of 17 years from issue under the pre-Uruguay Round patent-term regime. On that basis, the ordinary patent term ended in 2003, subject to any applicable patent-term adjustment, extension, disclaimer, or reissue history.

Event	Approximate timing
U.S. patent issuance	1986
Ordinary pre-1995 patent term	17 years from issue
Approximate ordinary expiration	2003
Current enforceability	Expired
Current Paragraph IV exposure	None attributable to this patent
Current Orange Book blocking effect	None attributable to this patent

The patent’s expiration means that the claims no longer provide enforceable exclusionary rights in the United States. Expiration also eliminates the commercial importance of historical claim construction disputes for new products, except where the patent remains relevant as prior art, technical history, or evidence concerning inventorship and enablement.

The controlling statutory framework for patents issued before the modern 20-year-from-earliest-effective-filing-date regime is 35 U.S.C. § 154, together with the transitional provisions enacted in the Uruguay Round Agreements Act (United States Code, 1994).

What is the Orange Book status of U.S. Patent 4,612,008?

U.S. Patent 4,612,008 is not an operative Orange Book patent barrier.

The patent claims an osmotic delivery platform rather than a specific FDA-approved active ingredient, dosage strength, formulation, or method of use. Orange Book listing generally concerns patents that claim an approved drug, approved formulation or composition, or approved method of use. Platform patents may be relevant to product development but are not automatically Orange Book-listable merely because an approved product uses a similar delivery principle.

The patent therefore should not be treated as:

A current listed patent for an approved drug.
A current patent supporting a Paragraph IV certification.
A current basis for an automatic 30-month stay.
A current barrier to an ANDA or 505(b)(2) application.

FDA Orange Book treatment is product-specific and depends on the approved drug application and the patent listing submitted by the NDA holder. The relevant statutory and regulatory framework includes 21 U.S.C. § 355 and 21 C.F.R. Part 314 (FDA, 2024).

Were Paragraph IV challenges or patent litigation associated with this patent?

No current Paragraph IV challenge can be based on U.S. Patent 4,612,008 because the patent has expired. A Paragraph IV certification addresses a listed patent associated with an approved drug application. An expired platform patent does not create a present ANDA litigation risk.

The supplied information does not establish a specific historical infringement action, ANDA case, settlement agreement, or consent judgment involving this patent. The patent should not be confused with later Alza osmotic-delivery patents that were asserted against generic versions of commercial products.

Historical litigation involving related osmotic systems may have concerned:

Later patents with different filing dates.
Specific drug formulations.
Push-pull osmotic systems.
Membrane compositions.
Pore-former technology.
Drug-specific dosage forms.
Commercial products such as controlled-release tablets.

A citation to U.S. Patent 4,612,008 in later litigation would not by itself establish that the patent was asserted, licensed, or found valid and infringed.

How strong was the patent estate technically?

The patent was technically broad for its filing period because it claimed a platform architecture rather than a single pharmaceutical compound. Its coverage extended across:

Human and nonhuman environments.
Oral gastrointestinal delivery.
Pharmaceutical and nonpharmaceutical agents.
Semipermeable and microporous membranes.
Preformed and in-situ passageways.
Water-soluble and cross-linked polymers.
Different molecular-weight relationships between osmopolymers.

Its principal limitation was structural specificity. An accused system would generally need to show a drug or beneficial-agent composition and a separate osmotic delivery composition within a wall, with the relevant fluid-imbibition and passageway features.

Likely validity pressure points

A historical validity analysis would likely have focused on:

Anticipation: Earlier osmotic pumps and controlled-release devices could disclose semipermeable walls, osmotic agents, drug compartments, and passageways.
Obviousness: Combining known osmotic drug layers with a second osmotic polymer layer could have been challenged under 35 U.S.C. § 103.
Claim construction: Terms such as "osmopolymer," "exhibits an osmotic pressure gradient," "substantially impermeable," and "controlled rate" could affect scope.
Enablement and written description: Broad coverage across drugs, polymers, wall materials, and environments could raise questions about whether the specification enabled the full genus.
Indefiniteness: Functional delivery language could create disputes if the claims did not define measurable rate or duration parameters.

Because the patent is expired, these issues have no current exclusionary effect unless they arise in historical licensing, patent valuation, or prior-art analysis.

How does this patent compare with later osmotic delivery patents?

U.S. Patent 4,612,008 should be viewed as an early platform patent in the osmotic delivery field. Later patent families often narrowed the technology around a commercial product or addressed specific improvements.

Technology category	U.S. Patent 4,612,008	Later product-focused patents
Core	Drug layer plus separate osmotic delivery layer	Often drug-specific or dosage-form-specific
Drug limitation	Broad beneficial agent or drug language	Usually named active ingredient or formulation
Wall	Semipermeable or microporous	Often specified membrane chemistry and permeability
Passageway	Preformed or formed in use	Frequently defined by size, number, drilling, or geometry
Polymer	Broad osmopolymer language	Often specified polymer, grade, viscosity, or molecular weight
Commercial relevance	Platform technology	Product-specific exclusivity and litigation
Current term	Expired	Depends on each later patent family

Later osmotic systems may avoid literal claim coverage by using:

A single homogeneous drug matrix.
A nonosmotic swellable push layer.
A membrane with a different transport mechanism.
A diffusion-controlled matrix.
A drug layer lacking an osmagent.
A delivery layer lacking an osmopolymer.
A nonlayered reservoir.
A different outlet or release mechanism.

Those design differences would have to be evaluated claim by claim and, during the patent term, under the doctrine of equivalents.

What generic-entry risks exist today?

There is no direct generic-entry risk from U.S. Patent 4,612,008 because it is expired. The relevant current risks would come from later, unexpired patents covering a specific commercial product or its formulation.

For a controlled-release osmotic product, a freedom-to-operate review would normally examine:

Orange Book-listed formulation patents.
Method-of-use patents.
Drug-specific crystalline-form patents.
Membrane and coating patents.
Manufacturing-process patents.
Dosage-form geometry patents.
Device patents covering osmotic push layers.
Regulatory exclusivity unrelated to patent term.

A generic manufacturer could use the expired patent’s technical disclosure without obtaining a license. A later patent could still create risk if it claims a narrower implementation, even where the broader 4,612,008 disclosure is available as prior art.

What licensing or commercial significance did the patent have?

The claims are consistent with technology developed in the Alza osmotic-delivery patent portfolio. The patent’s commercial value would have depended on licensing or integration into controlled-release products using layered osmotic cores.

The supplied information does not establish a specific assignment, license, royalty agreement, settlement, or commercial product directly tied to U.S. Patent 4,612,008. No such transaction should be attributed to this patent without a recorded agreement or litigation document.

The patent’s present commercial value is limited to:

Prior-art and freedom-to-operate analysis.
Historical valuation of osmotic delivery technology.
Evidence concerning platform development.
Identification of later continuation, divisional, or improvement patents.
Technical benchmarking for controlled-release formulation programs.

How should a product be screened against the claims?

A product-screening matrix should begin with claims 1, 7, 17, and 20.

Screening question	Relevance
Is there a wall that admits external fluid but restricts drug passage?	Required by the principal device claims
Is there a drug or beneficial-agent composition?	Required by claims 1, 7, and 17
Is there a separate second composition?	Central to claims 1, 7, 17, and 20
Does the second composition contain an osmagent and osmopolymer?	Required by the principal claims
Are the two compositions layered or laminar?	Required by claims 4 and 20, not identically required by every independent claim
Is there a passageway connected to the drug composition?	Required by the device claims
Do both compositions imbibe external fluid?	Expressly required by dependent claims and relevant to mechanism
Is the device used in a human or gastrointestinal tract?	Narrows claims 18 and 19
Is the wall cellulose-based?	Narrows claims 2 and 10
Is a pore former used?	Narrows claims 22, 24, 25, and 27

Because the patent is expired, the matrix is now primarily useful for historical analysis and for identifying the boundaries between expired platform disclosure and later enforceable patent claims.

Key Takeaways

U.S. Patent 4,612,008 covers a bilayer osmotic drug-delivery device.
Its core structure is a drug-containing osmotic composition plus a separate osmotic delivery composition inside a fluid-permeable wall.
Independent claims 1, 7, 17, and 20 define the principal device and composition categories.
Dependent claims address cellulose membranes, layered cores, cross-linked or water-soluble polymers, pore formers, in-situ passageways, human use, and oral gastrointestinal delivery.
The patent issued in 1986 and reached its ordinary expiration around 2003 under the pre-1995 patent-term regime.
It is expired and does not create a current U.S. Orange Book, Paragraph IV, generic-entry, or biosimilar barrier.
The patent does not claim a biologic-specific delivery system, so biosimilar risk is not a relevant exclusivity category.
Current freedom-to-operate risk must be assessed against later, unexpired patents covering specific drugs, formulations, membranes, manufacturing processes, or commercial dosage forms.
The supplied information does not establish a specific litigation history, license, settlement, assignment chain, or commercial product tied directly to this patent.

FAQs About U.S. Patent 4,612,008

Is U.S. Patent 4,612,008 still enforceable?

No. The patent is expired based on its 1986 issuance and the applicable pre-1995 patent-term rules.

Does U.S. Patent 4,612,008 cover OROS technology?

The claims cover an osmotic delivery architecture consistent with OROS-type technology, including a drug composition, a separate osmotic delivery composition, a semipermeable wall, and a passageway. The patent should not be treated as the only patent covering any particular OROS commercial product.

Can a generic manufacturer practice the claims of U.S. Patent 4,612,008?

Yes, subject to other unexpired patents. The expiration of this patent removes its current U.S. exclusionary effect.

Does the patent cover osmotic delivery of pesticides?

Yes. Claim 3 expressly identifies algicides, germicides, herbicides, fungicides, insecticides, and pesticides as beneficial agents.

Does the patent cover a tablet with a microporous membrane?

Potentially, if the tablet also satisfies the required bilayer composition, osmagent, osmopolymer, fluid-permeable wall, and passageway limitations. Claims 22, 24, 25, and 27 specifically address microporous walls and pore formers.

References

U.S. Patent No. 4,612,008. (1986). United States Patent and Trademark Office.
Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. U.S. Department of Health and Human Services.
United States Code, 21 U.S.C. § 355. (2024). New drugs.
United States Code, 35 U.S.C. § 154. (2024). Contents and term of patent; provisional rights.
Code of Federal Regulations, 21 C.F.R. pt. 314. (2024). Applications for FDA approval to market a new drug.

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
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Details for Patent: 4,612,008

Summary for Patent: 4,612,008