US Patent 5,698,225: Claim Scope, Expiration, Orange Book Status, and Patent Landscape

US Patent 5,698,225 protected a multilayer oral dosage form combining a nonsteroidal anti-inflammatory drug, or NSAID, with misoprostol. The central architecture was an NSAID-containing core surrounded by a misoprostol-containing mantle. Claim 3 added an enteric intermediate coating, and claim 4 required a stabilized prostaglandin formulation.

The patent issued on December 16, 1997, to G.D. Searle & Co. Its enforceable term has expired. The patent therefore does not presently block generic manufacture or sale, although its claim structure remains relevant to historical Arthrotec development, Orange Book analysis, prior-art studies, and freedom-to-operate reviews.

What drug product and technology did US Patent 5,698,225 protect?

The patent covered pharmaceutical compositions that physically separated an NSAID from misoprostol within a single oral dosage form. The likely commercial application was the Arthrotec product family, which combines diclofenac sodium with misoprostol.

The dosage-form design addressed two pharmacological objectives:

Diclofenac supplied anti-inflammatory and analgesic activity.
Misoprostol supplied prostaglandin activity intended to reduce NSAID-associated gastrointestinal injury.

The patent did not claim every pharmaceutical combination of an NSAID and misoprostol. Its principal limitation was the spatial arrangement of the components:

The NSAID had to be in a core.
Misoprostol had to be in a surrounding mantle coating.
The dosage form was intended for oral administration.
The ingredients had to be present in therapeutically effective amounts.

This architecture distinguished the claimed product from a simple powder blend, a conventional multilayer tablet, or a dosage form in which the NSAID and misoprostol were randomly distributed throughout the matrix.

What is the likely commercial product associated with the patent?

The relevant product was Arthrotec, a delayed-release combination of diclofenac sodium and misoprostol. Pfizer marketed Arthrotec after acquiring the relevant Searle business. The FDA-approved product has been supplied in strengths including:

Product	NSAID component	Misoprostol component	Dosage form
Arthrotec 50	Diclofenac sodium 50 mg	Misoprostol 200 mcg	Delayed-release tablet
Arthrotec 75	Diclofenac sodium 75 mg	Misoprostol 200 mcg	Delayed-release tablet

The patent claims were broader than the named commercial product in one respect: claim 1 recites a “nonsteroidal anti-inflammatory agent,” rather than diclofenac specifically. The patent therefore potentially covered other NSAIDs if they were configured in the claimed core-and-mantle arrangement.

How should claim 1 of US Patent 5,698,225 be construed?

Claim 1 is the principal composition claim:

“A pharmaceutical composition comprising: a. a core consisting of a therapeutically-effective amount of a nonsteroidal anti-inflammatory agent; and b. a mantle coating surrounding the core comprising a therapeutically-effective amount of misoprostol.”

Its important limitations are set out below.

Claim element	Scope and legal significance
Pharmaceutical composition	Requires a drug product or dosage form, not merely a method of treatment or a loose conceptual combination
Core	The NSAID must be located in an identifiable inner portion
Consisting of a therapeutically effective amount of an NSAID	The core limitation is narrower than a conventional “comprising” clause and focuses on the NSAID-bearing core
NSAID	Generic class limitation covering nonsteroidal anti-inflammatory agents, subject to the specification and prosecution history
Mantle coating	Requires a coating layer surrounding the core
Misoprostol	The mantle must contain misoprostol, not merely another prostaglandin analog
Therapeutically effective amount	The misoprostol quantity must be sufficient for its claimed therapeutic purpose
Comprising	The overall composition may contain additional excipients, coatings, stabilizers, and structural components

Does claim 1 require a single tablet?

The claim does not expressly use the word “tablet.” It requires a pharmaceutical composition having a core and a surrounding mantle. A tablet, pellet, granule, bead, capsule-contained unit, or similar oral dosage form could potentially satisfy the structural language if the product has the required core and coating arrangement.

The claim is less likely to cover:

A capsule containing two physically separate uncoated powders.
A homogeneous mixture of diclofenac and misoprostol.
A tablet in which misoprostol is dispersed throughout the core rather than positioned in a surrounding mantle.
A dosage form containing misoprostol only in an outer package or separate compartment without a coating relationship.

The scope depends on whether the accused product has a recognizable mantle that surrounds the NSAID core. Manufacturing documents, cross-sectional microscopy, coating-process records, and formulation specifications would be important in an infringement analysis.

What does claim 2 protect?

Claim 2 is a method-of-treatment claim requiring oral administration of the claimed dosage form to a patient in need of inflammation treatment.

Its required elements are:

A patient in need of treatment for inflammation.
Oral administration.
A therapeutically effective amount.
A composition containing the claim 1 core-and-mantle configuration.
An NSAID in the core.
Misoprostol in the surrounding mantle.

Claim 2 is not a broad claim to treating inflammation with any diclofenac-misoprostol product. It incorporates the physical dosage-form limitations of claim 1. A product could contain the same active ingredients but avoid claim 2 if it lacks the required core and surrounding misoprostol mantle.

Because the patent has expired, claim 2 has no current blocking effect. Before expiration, potential defendants could have faced direct infringement allegations based on administration, inducement allegations based on product labeling, or contributory infringement theories depending on the facts.

What additional protection does claim 3 provide?

Claim 3 adds:

“an intermediate coating surrounding the core wherein the intermediate coating comprises an enteric coating.”

This produces a three-part structure:

NSAID-containing core.
Intermediate enteric coating surrounding the core.
Misoprostol-containing mantle surrounding the core, with the mantle positioned outside or around the intermediate layer.

The enteric coating can delay exposure of the NSAID core until the dosage form reaches a higher-pH intestinal environment. In a commercial product, that design could help manage release timing, drug stability, local gastric exposure, and compatibility between diclofenac and misoprostol.

Claim 3 is narrower than claim 1. A product that satisfies claim 3 necessarily falls within claim 1, assuming the other claim 1 elements are present. A product may satisfy claim 1 without satisfying claim 3 if it lacks an enteric intermediate layer.

What formulations are most exposed to claim 3?

The highest-risk formulation would have:

A diclofenac-containing central tablet or pellet.
An enteric polymer layer directly around that core.
A misoprostol-containing outer coating.
Oral administration as a single dosage unit.

Potential enteric polymers could include conventional acid-resistant materials such as cellulose acetate phthalate, methacrylic acid copolymers, or polyvinyl acetate phthalate. The patent claim does not require a specific polymer, thickness, pH threshold, or dissolution profile.

What does claim 4 add regarding stabilized prostaglandin formulations?

Claim 4 requires the prostaglandin mantle to comprise a stabilized prostaglandin formulation. Misoprostol is chemically and physically sensitive, making stabilization central to the dosage-form technology.

Possible stabilization strategies include:

Use of stabilizing excipients.
Protection from moisture.
Selection of a suitable coating vehicle.
Control of pH and processing temperature.
Encapsulation or barrier coating.
Use of a stabilized misoprostol premix.

Claim 4 is narrower than claim 1 because it adds a formulation-quality limitation. Its practical scope depends heavily on how “stabilized prostaglandin formulation” is defined in the patent specification and prosecution history. If the specification identifies particular stabilizers or measurable stability criteria, those disclosures may limit construction. If stabilization is described functionally without a precise test, disputes could arise over whether an accused formulation satisfies the limitation.

When did US Patent 5,698,225 lose exclusivity?

The patent issued on December 16, 1997. Its ordinary patent term was governed by the pre-Uruguay Round Agreements Act framework applicable to the relevant filing history, generally producing a term measured from issuance rather than the current 20-year-from-earliest-effective-filing rule.

The patent’s ordinary expiration was December 16, 2014, subject to any applicable patent-term adjustment or extension. Public patent and FDA records treat the patent as expired. No current enforceable exclusion remains.

Event	Date or status
Patent issued	December 16, 1997
Patent holder at issuance	G.D. Searle & Co.
Main technology	NSAID core with misoprostol mantle
Expected ordinary expiration	December 16, 2014
Current status	Expired
Current generic blocking power	None

Patent expiration eliminates the right to exclude future manufacture, use, sale, offers for sale, and imports under 35 U.S.C. § 271. It does not erase historical infringement claims that accrued while the patent was in force, subject to applicable limitations periods and procedural requirements.

What was the Orange Book status of US Patent 5,698,225?

The patent was associated with the Arthrotec regulatory and commercial franchise. The FDA Orange Book historically listed patents for approved drug products when the patents claimed the drug substance, formulation, composition, or method of use in the manner required by the listing rules.

For a diclofenac sodium and misoprostol product, the relevant Orange Book analysis would include:

The approved combination product.
The dosage form and strengths.
Listed formulation or composition patents.
Method-of-use patents, if any.
Patent expiration dates.
Any pediatric-exclusivity or patent-term-extension information.

The patent is no longer a live Orange Book barrier to generic entry. Current applicants are not required to treat an expired patent as an enforceable obstacle, although historical ANDA certifications and litigation records may still reference it.

Were there Paragraph IV challenges involving this patent?

A Paragraph IV certification would assert that a listed patent was invalid, unenforceable, or would not be infringed by the proposed generic product. Combination products such as Arthrotec can generate Paragraph IV disputes involving:

The core-and-mantle formulation.
Misoprostol stability.
Enteric coating structure.
The scope of the method-of-treatment claims.
Anticipation or obviousness based on earlier NSAID and prostaglandin formulations.

The expiration of US 5,698,225 means that a new generic applicant no longer needs to overcome this patent to obtain commercial freedom. Historical litigation should be distinguished from current risk. A patent that was challenged before 2014 may have affected launch timing, but it does not create a present exclusivity period.

No current litigation effect should be attributed to US 5,698,225 without a docket-specific review of the relevant district court and Federal Circuit records.

What were the principal validity vulnerabilities?

The strongest validity issues would likely have involved obviousness, anticipation, claim construction, and support for the formulation limitations.

Anticipation

An anticipation reference would need to disclose every limitation in a single prior-art reference, including:

An NSAID-containing core.
A surrounding misoprostol mantle.
Therapeutically effective quantities.
The claimed pharmaceutical composition or oral treatment method.

A reference disclosing only coadministration of an NSAID and misoprostol would not necessarily anticipate the structural mantle limitation.

Obviousness

Obviousness would be the more substantial challenge. The relevant prior art could include:

NSAID sustained-release or enteric-coated dosage forms.
Prostaglandin gastroprotective formulations.
Layered tablets.
Coated pellets and multiparticulate systems.
Prior combination therapy using NSAIDs and prostaglandins.
Stability techniques for misoprostol.

The patent holder could respond that the specific arrangement solved compatibility, release-control, and stability problems not addressed by the individual references.

Enablement and written description

The patent would need to support the breadth of “nonsteroidal anti-inflammatory agent” and “stabilized prostaglandin formulation.” If the specification primarily describes diclofenac and a limited number of formulations, an accused infringer could argue that the claims extend beyond the technical disclosure.

Indefiniteness

Terms such as “therapeutically effective amount” are common pharmaceutical claim language and are not automatically indefinite. “Stabilized prostaglandin formulation” could present a closer issue if the patent lacks an objective definition or test for stability.

How strong was the patent estate for Arthrotec?

The patent estate was stronger as a product-design patent than as a broad combination-therapy patent. Its commercial value came from the physical configuration of the dosage form.

Estate component	Assessment
Core-and-mantle composition	Strongest commercial feature
Generic NSAID coverage	Broad in wording, limited by structural arrangement
Diclofenac-specific coverage	Dependent on related patents or specification support
Enteric intermediate coating	Narrower but technically meaningful
Misoprostol stabilization	Potentially valuable, but construction-sensitive
Method of treatment	Dependent on infringement of the dosage-form structure
Current enforceability	None after expiration

The patent would have been most useful against a generic that copied the commercial multilayer architecture. It would have been less effective against an alternative product using a physically separate capsule, a dual-compartment system, a homogeneous matrix, or a different release design.

How did the patent compare with other exclusivity tools?

US Patent 5,698,225 was a formulation patent, not a composition-of-matter patent on diclofenac or misoprostol. That distinction matters.

Protection type	Relevance to Arthrotec
Active-ingredient patent	Would protect diclofenac or misoprostol itself, but those older ingredients were not the primary barrier
Combination patent	Could cover diclofenac-misoprostol use or composition
Formulation patent	Covered the core, coating, and release architecture
Method-of-use patent	Could cover treatment of inflammation or NSAID-associated gastric injury
FDA exclusivity	Separate from patent rights and dependent on the approval history
Orphan exclusivity	Not relevant to the general Arthrotec indication
Biosimilar exclusivity	Not applicable; Arthrotec is a small-molecule drug

Because Arthrotec is a small-molecule combination product, biosimilar rules do not apply. Generic applicants use the ANDA pathway, subject to bioequivalence and applicable patent certifications.

What generic launch scenarios existed?

Before expiration, generic entry could have followed several paths:

A product designed around the patent, avoiding the mantle architecture.
A Paragraph IV challenge asserting invalidity or noninfringement.
A launch after patent expiration.
A settlement providing a licensed or agreed entry date.
A product with a different dosage-form design and a label that avoided patented uses.

After December 2014, the central patent no longer constrained launch timing. Remaining barriers would have included FDA approval, bioequivalence, manufacturing readiness, supply of misoprostol, product labeling, and any separate unexpired patents.

What manufacturing and IP barriers remain relevant?

The expired patent does not remove technical barriers. A manufacturer still must address:

Misoprostol potency and degradation.
Uniform coating of the NSAID core.
Adhesion and integrity of the mantle layer.
Enteric dissolution performance.
Dose uniformity at the microgram misoprostol level.
Stability under heat and humidity.
Compatibility of coating solvents and excipients.
Bioequivalence against the reference product.
Reproductive-safety labeling and handling controls associated with misoprostol.

These are manufacturing and regulatory barriers, not continuing exclusivity rights under US 5,698,225.

What patent litigation and settlement issues matter?

The most important historical litigation questions are:

Whether a generic copied the claimed core-and-mantle structure.
Whether the product had an enteric intermediate coating.
Whether the misoprostol layer was stabilized within claim 4.
Whether a generic label induced use covered by claim 2.
Whether patent-term calculations delayed generic entry.
Whether a settlement granted an authorized or licensed launch.

An expired patent can remain relevant in damages litigation for past infringement, but it cannot support a current injunction against ordinary future commercialization.

Key Takeaways

US Patent 5,698,225 covered an oral dosage form with an NSAID-containing core and a surrounding misoprostol mantle.
Claim 1 is the central composition claim; claim 2 covers oral treatment using that dosage form.
Claim 3 narrows the product by requiring an intermediate enteric coating.
Claim 4 narrows the product by requiring a stabilized prostaglandin formulation.
The patent was associated with the Arthrotec diclofenac sodium/misoprostol product concept.
The patent’s ordinary term ended on or about December 16, 2014.
It is expired and presents no current US blocking right.
The strongest historical infringement case would have involved a generic copying the same multilayer architecture.
Biosimilar risk is irrelevant because Arthrotec is a small-molecule combination product.
Current commercial barriers relate to FDA approval, bioequivalence, stability, coating manufacture, and separate unexpired rights, not this patent.

FAQs About US Patent 5,698,225

Does US Patent 5,698,225 cover diclofenac by itself?

No. The claims require a specific dosage-form structure combining an NSAID-containing core with a surrounding misoprostol mantle. Diclofenac without that architecture is outside the principal claim language.

Does a simple diclofenac-misoprostol mixture infringe claim 1?

Not necessarily. A homogeneous mixture may avoid claim 1 if it lacks a distinct NSAID core and a misoprostol mantle surrounding that core.

Is US Patent 5,698,225 still enforceable?

No. The patent has expired, with an ordinary expiration date of December 16, 2014.

Is Arthrotec protected by biosimilar exclusivity?

No. Arthrotec is a small-molecule combination drug. Generic competition proceeds under the ANDA framework rather than the biosimilar pathway.

Can a company launch a generic product without addressing this patent?

Yes, because the patent is expired. The company must still address FDA approval, bioequivalence, manufacturing controls, labeling, and any separate live patents.

References

U.S. Patent No. 5,698,225. (1997). Pharmaceutical compositions containing a nonsteroidal anti-inflammatory agent and misoprostol. United States Patent and Trademark Office.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
U.S. Food and Drug Administration. (n.d.). Arthrotec prescribing information. FDA.
United States Code. (2024). 35 U.S.C. §§ 154, 271, 271(e), and 156.
United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent term expiration guidance. USPTO.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	121625	⤷ Start Trial
Australia	7876491	⤷ Start Trial
Canada	2082944	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,698,225

Summary for Patent: 5,698,225