United States Patent 4,620,974: Scope, Claims, Expiration, and Oxazepam Patent Landscape

U.S. Patent No. 4,620,974 protected a hard gelatin capsule containing a dust-producing pharmaceutical powder lubricated with liquid polyethylene glycol rather than a conventional solid hydrophobic lubricant. The claims focused on capsule manufacture, powder handling, and formulation performance. Claims 5 through 10 narrowed the invention to oxazepam, including 10 mg, 15 mg, and 30 mg capsule compositions.

The patent issued on November 4, 1986, and its pre-URAA term was generally 17 years from grant. On that basis, the patent expired on November 4, 2003. The patent no longer creates a U.S. patent barrier to generic oxazepam capsules. Its technical disclosure remains relevant to formulation design, but its claims cannot support a current U.S. infringement action. [1][2]

What invention does U.S. Patent 4,620,974 protect?

The patent protects a filled hard gelatin capsule in which a dry, dusty therapeutic powder is blended with a small quantity of liquid, hydrophilic polyethylene glycol, or PEG.

The claimed formulation has five central characteristics:

A hard gelatin, telescoping two-piece capsule.
A solid pharmaceutical composition inside the capsule.
A dry, powdery therapeutic agent capable of producing dust.
No solid hydrophobic lubricant in the composition.
Liquid PEG with a molecular weight of approximately 200 to 900, used at approximately 0.5% to 25% by weight.

The invention addresses a manufacturing problem. Conventional solid hydrophobic lubricants, such as magnesium stearate, can reduce powder adhesion and friction but may create dissolution, wetting, content-uniformity, or bioavailability concerns. The claimed PEG is hydrophilic and liquid at the relevant molecular weights. It reduces dust and improves processing without functioning as a conventional insoluble solid lubricant.

The patent is therefore a formulation and manufacturing patent, not a patent on oxazepam as a chemical entity.

What are the key limitations of independent claim 1?

Claim 1 is the broadest claim and requires the accused product or process to satisfy every limitation.

Claim 1 limitation	Scope
Capsule type	Hard gelatin, telescoping, two-piece capsule
Dosage form	Filled capsule containing a solid pharmaceutical composition
Active ingredient	A dry, powdery, dust-producing therapeutic agent
Excluded excipient	The composition must be free of solid hydrophobic lubricant
Lubricant	Pharmaceutically acceptable, liquid, hydrophilic, dust-reducing lubricant
Lubricant identity	PEG with molecular weight from about 200 to about 900
PEG quantity	About 0.5% to about 25% by weight of the composition
Physical relationship	PEG must be in intimate admixture with the therapeutic agent
Functional role	PEG must reduce dust and act as a lubricant without solubilizing the composition

The claim does not require oxazepam. Any qualifying therapeutic powder could potentially fall within claim 1 if the remaining structural and functional limitations were met during the patent term.

The phrase "free of solid hydrophobic lubricant" is a material limitation. A formulation containing magnesium stearate, stearic acid, or another solid hydrophobic lubricant could raise a non-infringement position if the ingredient falls within the claim exclusion. The analysis would depend on the identity, amount, and technical characterization of the excipient.

The phrase "non-solubilizing amount" also limits the claim. PEG must reduce dust and provide lubrication without converting the composition into a solution or materially solubilizing the therapeutic agent. The limitation creates a factual issue involving concentration, PEG grade, drug solubility, and the physical state of the blend.

How do claims 2 through 4 narrow the patent scope?

Claim 2 limits the PEG to a molecular weight of approximately 380 to 420. This range corresponds commercially to PEG 400 or a closely related PEG grade.

Claim 3 adds a pharmaceutically acceptable surface-active agent.

Claim 4 narrows claim 3 to a list of specified surfactant classes and compounds:

Fatty esters of polyoxyethylene sorbitan;
Polyoxyethylene condensates of a hydrophobic base formed from propylene oxide and propylene glycol;
Sorbitan monolaurate;
Octylphenoxypolyethoxy ethanol;
Cetylpyridinium chloride; or
Dioctyl sodium sulfosuccinate.

Claim 4 is a closed list for the specified surfactant limitation. A formulation using a different surfactant would not literally satisfy that particular dependent claim, although it could still fall within claim 3 if the surfactant were pharmaceutically acceptable.

What oxazepam formulations are protected by claims 5 through 10?

Claims 5 through 10 create a progressively narrower oxazepam subgenus.

Claim 5: oxazepam capsule

Claim 5 applies claim 1 to oxazepam. A product must still contain the claimed PEG, the specified capsule, the solid powder, and the exclusion of solid hydrophobic lubricant.

The claim does not specify a particular oxazepam dose, filler, disintegrant, or surfactant.

Claim 6: broader oxazepam composition

Claim 6 requires:

Approximately 10 to 30 mg oxazepam;
Approximately 0.5% to 25% PEG 200-900 by weight of the composition;
Approximately 0.1% to 25% surfactant by weight of the composition; and
A filler.

This claim is broader than claims 7 through 10 because it allows a wide PEG molecular-weight range and a broad surfactant concentration.

Claim 7: narrower PEG and surfactant ratios

Claim 7 requires:

Approximately 10 to 30 mg oxazepam;
PEG with molecular weight of approximately 380 to 420;
PEG at approximately 3% to 11% relative to the oxazepam amount;
A nonionic surfactant at approximately 0.5% to 2.5% relative to the oxazepam amount; and
A filler.

The wording "ratio to active" is important. The percentages are stated relative to the oxazepam weight rather than necessarily the total capsule composition. A 10 mg oxazepam capsule, for example, would correspond to approximately 0.3 to 1.1 mg PEG under the claimed 3% to 11% ratio.

Claims 8 through 10: specific commercial-style formulas

Claims 8 through 10 recite specific dosage strengths and excipient quantities.

Claim	Oxazepam	Lactose	Croscarmellose sodium	PEG 380-420	Surfactant
8	About 10 mg	About 167 mg	About 6.6 mg	About 1.1 mg	About 0.22 mg
9	About 15 mg	About 162 mg	About 6.6 mg	About 1.1 mg	About 0.22 mg
10	About 30 mg	About 147 mg	About 6.6 mg	About 1.1 mg	About 0.22 mg

Because claims 8 through 10 depend on claim 7, they also inherit the claim 7 requirements, including PEG 380-420, the relative PEG and surfactant ratios, a nonionic surfactant, and a filler.

The claims use "about," which generally provides some numerical flexibility. The scope would turn on the intrinsic patent evidence, specification examples, prosecution history, measurement method, and the ordinary meaning of the ranges at the relevant time. Exact commercial matching is not necessarily required for a claim to apply.

How strong is the patent estate for oxazepam?

The U.S. patent estate represented by Patent 4,620,974 is no longer commercially enforceable because the patent expired in 2003. Its historical scope was narrower than an active-ingredient patent and depended on several formulation-specific limitations.

Estate characteristic	Assessment
Active ingredient protection	None; the patent does not claim oxazepam as a molecule
Dosage-form protection	Hard gelatin, two-piece capsules only
Formulation protection	PEG-based dust reduction and lubrication
Hydrophobic-lubricant exclusion	Strong narrowing limitation
Oxazepam protection	Claims 5-10
Specific strength protection	10 mg, 15 mg, and 30 mg compositions
Manufacturing relevance	High during the patent term
Current blocking value	None in the United States
Design-around potential during term	Meaningful, particularly through excipient, capsule, or process changes
Current patent life	Expired

The patent did not cover tablets, soft gelatin capsules, liquids, injectables, transdermal systems, or other dosage forms unless they also met the hard gelatin capsule limitation. It also did not broadly cover every oxazepam formulation.

When did U.S. Patent 4,620,974 lose exclusivity?

The patent issued on November 4, 1986. For a pre-June 8, 1995 U.S. patent, the governing term was generally 17 years from the issue date, subject to statutory adjustments and terminal disclaimers. The resulting ordinary expiration date was November 4, 2003. [1][2]

Exclusivity timeline

Event	Date or status
U.S. patent issued	November 4, 1986
Ordinary 17-year patent term	November 4, 2003
Current patent status	Expired
Current patent-based generic blocking right	None
FDA small-molecule exclusivity	Separate from this patent and not extended by the patent
Biosimilar exclusivity	Not applicable

FDA regulatory exclusivity and patent term are separate systems. A formulation patent does not automatically create FDA marketing exclusivity, and an FDA exclusivity period does not extend an expired patent. [3]

What is the Orange Book status of the patent?

A patent may be listed in the FDA Orange Book only if the NDA holder submits it and it meets FDA listing requirements. FDA listing does not establish patent validity or infringement. It provides notice of patents asserted to cover an approved drug, its formulation, or an approved method of use. [3]

Patent 4,620,974 is not a current U.S. blocking patent. Any historical Orange Book listing associated with an oxazepam product would have ceased to provide effective patent protection no later than the patent's expiration in 2003. The practical Orange Book questions for a current oxazepam abbreviated new drug application are whether a currently listed patent exists for the relevant reference product and whether any listed patent has an unexpired term.

Because Patent 4,620,974 expired more than two decades ago, it cannot support a current Paragraph IV certification alleging invalidity or non-infringement against a live patent right.

What Paragraph IV challenge risks existed?

During the patent term, a generic applicant seeking approval for a capsule matching the claimed oxazepam formulation could have faced a Paragraph IV issue if Patent 4,620,974 had been listed for the reference product.

The risk would have depended on whether the proposed product included:

Hard gelatin, two-piece capsules;
Oxazepam powder;
PEG 200-900;
PEG 380-420 for the narrower claims;
A surfactant;
A nonionic surfactant;
The claimed dose and excipient ratios; and
No solid hydrophobic lubricant.

A generic manufacturer could have reduced risk by using a different dosage form, a different lubricant, a solid rather than liquid lubricant, a PEG outside the claimed range, a different excipient system, or a formulation that did not satisfy the claimed dust-reduction and non-solubilizing functions.

No current Paragraph IV exposure arises from this patent because the patent has expired. Any present oxazepam ANDA strategy would be assessed against current Orange Book listings, FDA regulatory requirements, and any other unexpired patents, not against Patent 4,620,974.

What formulation design-arounds were available?

The patent's limitations provide several potential design-around routes.

Change the lubricant

A manufacturer could use a lubricant that is not liquid, hydrophilic PEG within the claimed range. The primary design-around choices would include an excipient outside the PEG 200-900 range or a formulation that uses a different technical approach to reduce powder adhesion.

A solid hydrophobic lubricant might avoid the claims because claim 1 expressly requires the composition to be free of such a lubricant. That approach could create separate dissolution or content-uniformity issues.

Change the dosage form

The claims require a hard gelatin, telescoping two-piece capsule. Tablets, soft capsules, liquids, and other delivery systems would not literally meet that limitation.

Change the PEG grade or amount

A formulation using PEG below approximately 200 or above approximately 900 could avoid claim 1, subject to the interpretation of "about." PEG 400 is central to claims 2 and 7-10. A formulation outside the claimed concentration or active-relative ratio could avoid the narrower claims.

Change the surfactant

Claims 3 and 6-10 require surfactant limitations. A formulation without a surfactant could avoid those claims while still requiring analysis under claims 1, 2, or 5. A formulation using a surfactant outside claim 4's listed compounds could avoid claim 4 but not necessarily claim 3.

Change the active ingredient

Claims 5 through 10 require oxazepam. Claim 1 is broader and could apply to other dusty therapeutic agents, but it would still require all of the claim 1 formulation and capsule limitations.

What patent litigation affected U.S. Patent 4,620,974?

The patent's expiration eliminates present litigation risk based solely on the claimed subject matter. A patent infringement action generally requires an unexpired enforceable claim for prospective relief. Patent 4,620,974 cannot now prevent a generic company from marketing an oxazepam capsule.

The historical dispute value of the patent would have centered on claim construction and factual questions involving:

Whether PEG was liquid at the relevant molecular weight;
Whether the PEG concentration was within the claimed range;
Whether the composition contained a solid hydrophobic lubricant;
Whether the PEG reduced dust;
Whether the PEG amount was non-solubilizing;
Whether the capsule was a hard gelatin, two-piece capsule; and
Whether the product contained the required surfactant and filler.

There is no current settlement or license value attributable to the expired U.S. claims unless a separate contract, product liability matter, or historical dispute remains relevant. The patent itself no longer supports a prospective U.S. market exclusion.

Did the patent create biosimilar risk?

No. Oxazepam is a chemically synthesized small molecule, not a biologic. The Biologics Price Competition and Innovation Act biosimilar pathway does not apply. [4]

The relevant regulatory pathway for a generic oxazepam product would be an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act, assuming the product qualifies for abbreviated approval. The patent did not create a biosimilar barrier, and its expired status does not create a current ANDA patent barrier. [3][5]

What is the geographic coverage of the patent?

Patent 4,620,974 provided rights only in the United States. A U.S. patent does not establish rights in Canada, Europe, Japan, or other jurisdictions.

Foreign equivalents, continuations, divisionals, or related applications must be assessed separately. The U.S. claims cannot be used to establish infringement outside the United States. Any foreign family member would have had its own filing date, term, prosecution history, maintenance requirements, and legal status.

Are manufacturing and trade-secret barriers still relevant?

The patent's manufacturing concept may remain technically useful even though the claims have expired. A company can use the disclosed PEG-based dust-reduction approach without licensing the expired patent.

Residual commercial barriers may arise from:

Process validation;
Powder-flow control;
Blend uniformity;
Capsule-filling equipment;
PEG distribution across particles;
Surfactant dispersion;
Dissolution performance;
Stability and shell compatibility; and
FDA comparative quality requirements.

Those are regulatory and operational barriers, not continuing patent rights under U.S. Patent 4,620,974. The patent does not provide a current trade-secret claim over the disclosed formulation.

Key Takeaways

U.S. Patent 4,620,974 claimed a hard gelatin capsule containing a dusty pharmaceutical powder and liquid hydrophilic PEG.
The broadest claim required PEG molecular weight of approximately 200 to 900 and concentration of approximately 0.5% to 25%.
Claims 5 through 10 narrowed the invention to oxazepam.
Claims 8 through 10 covered specific 10 mg, 15 mg, and 30 mg formulations using lactose, croscarmellose sodium, PEG 380-420, and a polyoxyethylene sorbitan ester surfactant.
The patent was a formulation and manufacturing patent, not a chemical patent on oxazepam.
The patent's ordinary expiration date was November 4, 2003.
It no longer creates U.S. generic launch, Paragraph IV, licensing, or infringement risk.
Biosimilar analysis is irrelevant because oxazepam is a small-molecule drug.
Any current oxazepam patent analysis must focus on live Orange Book listings and other unexpired patents, not Patent 4,620,974.

FAQs About U.S. Patent 4,620,974

Could a generic company launch an oxazepam capsule containing PEG 400 today?

Yes, Patent 4,620,974 does not prevent launch because its U.S. claims expired in 2003. Current approval would depend on FDA requirements and any separate unexpired patents or regulatory exclusivities.

Does the patent cover Serax by brand name?

No. The claims do not claim the Serax trademark or a commercial brand. They claim physical capsule and formulation characteristics, including oxazepam in the narrower claims.

Would a tablet containing oxazepam infringe the patent?

No literal infringement would arise from the hard gelatin capsule limitation because a tablet is not a telescoping two-piece hard gelatin capsule. The patent also does not claim oxazepam in all dosage forms.

Is PEG 400 the same formulation component identified in the patent?

PEG 400 falls within the claimed molecular-weight range of approximately 380 to 420, assuming the material's measured or specified molecular weight satisfies the applicable claim interpretation.

Does expiration of the patent eliminate FDA bioequivalence requirements?

No. Patent expiration removes the patent barrier but does not eliminate ANDA requirements, including pharmaceutical equivalence, bioequivalence, quality controls, labeling, manufacturing compliance, and other FDA requirements.

References

United States Patent and Trademark Office. (1986). U.S. Patent No. 4,620,974.
United States Code, 35 U.S.C. § 154.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
United States Code, Public Law 111-148, § 7002, 124 Stat. 119 (2010).
United States Code, 21 U.S.C. § 355(j).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	3035684	⤷ Start Trial
Australia	569902	⤷ Start Trial
Canada	1235661	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,620,974

Summary for Patent: 4,620,974