United States Drug Patent 4,966,768: Claim Scope, Expiration, and Etodolac Patent Landscape

U.S. Patent No. 4,966,768 protects a once-daily sustained-release etodolac tablet defined by a specific hydrophilic-hydrophobic polymer matrix and a physiologically acceptable buffer. The central limitation is not etodolac alone. It is the combination of etodolac, hydroxypropylmethylcellulose, ethylcellulose, and a buffer-based release modifier compressed into a solid unit dosage form.

The patent issued on October 30, 1990. Under the pre-Uruguay Round patent term applicable to this patent, its ordinary 17-year term ran to October 30, 2007, absent an earlier terminal disclaimer or unusual adjustment. The patent is therefore expired and does not presently block generic manufacture, sale, or development of etodolac extended-release products. The historical product most closely associated with this technology is Lodine XL, an extended-release etodolac product.

What does U.S. Patent 4,966,768 protect?

The patent protects a sustained-release solid dosage form containing etodolac in a polymer matrix. Claim 1 requires all of the following:

Claim element	Required limitation
Active ingredient	Etodolac
Dosage form	Shaped and compressed solid unit dosage form
Intended release	Once-daily use with a regular and prolonged release pattern
Carrier base amount	About 18% to 30% by weight of the solid dosage form
Hydrophilic polymer	Hydroxypropylmethylcellulose, or HPMC
HPMC hydroxypropoxyl content	About 7.0% to about 8.6% by weight
HPMC methoxyl content	About 19% to 24% by weight
HPMC viscosity	80 to 120 centipoise for a 2% aqueous solution
HPMC molecular weight	Less than 50,000
Hydrophobic polymer	Ethylcellulose, present at 15% to 28% of the HPMC/ethylcellulose admixture
Release modifier	Effective amount of a physiologically acceptable buffer acid, buffer acid salt, or mixture
Manufacturing state	Components are admixed and compressed into the dosage form

Claim 2 narrows claim 1 by specifying dibasic sodium phosphate as the release-rate modifying agent.

Claim 3 repeats the 18% to 30% carrier-base limitation. It adds little practical scope if claim 1 is read as already containing that limitation.

How should the claims be construed?

The claim is a combination claim

Claim 1 is not a broad claim to sustained-release etodolac. A product must satisfy the entire combination of active ingredient, polymer composition, polymer specifications, dosage-form structure, and buffer limitation.

A sustained-release etodolac tablet using a different release-control system, such as a purely hydrophilic matrix, a coated multiparticulate system, an osmotic pump, or an enteric-coated pellet, would not fall within the literal scope unless it also satisfies the claimed HPMC/ethylcellulose combination and the other limitations.

"Consists essentially of" is narrower than "comprising"

The transition "consists essentially of" excludes ingredients that materially alter the basic and novel characteristics of the claimed formulation. The basic characteristics appear to be the controlled release of etodolac through the specified HPMC/ethylcellulose matrix with a buffer-based release modifier.

The language may permit ordinary excipients, including diluents, lubricants, binders, glidants, pigments, and compression aids, if they do not materially change the release mechanism. An additional polymer, coating, surfactant, or osmotic agent could create a dispute if it materially changes the claimed release pattern.

The functional release language has strategic importance

The claim requires a "regular and prolonged release pattern upon administration" and describes the product as useful for once-a-day medication. These limitations create two issues:

The composition must have the specified structural ingredients and quantities.
The finished dosage form must provide the claimed release behavior.

The release language could support an infringement argument against a formulation that contains the claimed polymers and buffer but releases etodolac too rapidly or irregularly. Conversely, an accused manufacturer could challenge whether terms such as "regular" and "prolonged" provide sufficiently objective boundaries. Because the patent has expired, those issues no longer create meaningful prospective market risk, but they remain relevant to historical validity or infringement analysis.

What are the critical quantitative limitations?

The strongest claim boundaries are the polymer identity and specification ranges.

HPMC specification

The HPMC is not defined merely by its presence. Claim 1 requires:

Hydroxypropoxyl content of approximately 7.0% to 8.6%;
Methoxyl content of approximately 19% to 24%;
2% aqueous-solution viscosity of 80 to 120 cps; and
Average molecular weight below 50,000.

These characteristics identify a particular grade or narrow class of HPMC. A formulation using a higher-viscosity HPMC, a materially different substitution profile, or a molecular weight of 50,000 or more would have a strong literal noninfringement position.

The viscosity limitation is especially important because HPMC viscosity affects gel formation, water penetration, tablet erosion, and diffusion of etodolac. A different HPMC grade may produce a similar dissolution curve while avoiding one or more express claim limitations.

Ethylcellulose limitation

Ethylcellulose must be present in an amount equal to 15% to 28% of the HPMC/ethylcellulose admixture. This is a ratio limitation rather than a simple percentage of the total tablet weight.

For example, if the carrier-base admixture contains 75 parts HPMC and 25 parts ethylcellulose, ethylcellulose represents 25% of that admixture and falls within the claimed range. The claim language requires careful denominator analysis. A manufacturer could avoid literal infringement by using less than 15% or more than 28% ethylcellulose in the relevant polymer admixture, subject to possible doctrine-of-equivalents arguments.

Carrier-base limitation

The carrier base must account for approximately 18% to 30% of the total solid dosage form. This range limits the total amount of the HPMC/ethylcellulose carrier system, not merely the amount of one polymer.

The phrase "about" creates a boundary question. Courts generally assess "about" in light of the specification, technical practice, prosecution history, and evidence concerning measurement precision. A formulation near 18% or 30% would require an exact compositional and analytical assessment.

What does claim 2 add by specifying dibasic sodium phosphate?

Claim 2 expressly identifies dibasic sodium phosphate as the release-rate modifying agent. It is narrower than claim 1 because it excludes other buffer acids, buffer salts, and mixtures.

Dibasic sodium phosphate may affect:

Tablet microenvironmental pH;
Etodolac dissolution;
Water penetration into the matrix;
Polymer hydration;
Drug diffusion and erosion; and
Reproducibility of the dissolution profile.

A product using monobasic sodium phosphate, potassium phosphate, citrate, acetate, or another buffer may avoid literal infringement of claim 2 while remaining within claim 1 if the alternative is a physiologically acceptable buffer salt and the other limitations are met.

What is the scope of claim 3?

Claim 3 states that the carrier base is within 18% to 30% by weight of the solid unit dosage form. Based on the supplied claim text, this limitation already appears in claim 1.

Claim 3 is therefore likely redundant or intended to clarify the carrier-base percentage. It does not materially broaden the patent. At most, it creates a separate dependent claim expressly directed to the carrier-base range.

When did U.S. Patent 4,966,768 expire?

Event	Date or status
Patent issued	October 30, 1990
Ordinary pre-URAA term	17 years from issue
Expected ordinary expiration	October 30, 2007
Current enforceability	Expired
Current generic blocking effect	None
Historical relevance	Extended-release etodolac formulation technology and Lodine XL

The patent predates the June 8, 1995 change from a 17-year-from-grant term to a 20-year-from-earliest-effective-filing term. A patent issued before that transition generally remains subject to the older term rules unless later statutory provisions altered the result. The USPTO patent record should be used for the controlling legal-status entry and any terminal-disclaimer information.[1]

Patent expiration is distinct from regulatory exclusivity. Any FDA marketing exclusivity associated with an extended-release etodolac product would have expired independently of the patent term. Neither regulatory exclusivity nor the patent currently prevents an abbreviated new drug application applicant from relying on the expired patent landscape.

What was the Orange Book status of etodolac extended-release products?

The Orange Book historically listed patents associated with approved drug products where the NDA holder submitted qualifying patent information. For an extended-release etodolac product, the relevant listing would have depended on the NDA holder's submission and the FDA's treatment of the patent.[2]

The practical status is now different:

U.S. Patent 4,966,768 is expired.
It cannot support a current 30-month stay based on a new Paragraph IV certification.
It does not provide current market exclusivity.
Any active Orange Book listing would not revive an expired patent.
A generic applicant may still need to address other unexpired listed patents, if any exist for a particular approved product.

The Orange Book should be checked by product name, active ingredient, dosage form, and NDA because immediate-release and extended-release etodolac products may have had different regulatory records.[2]

What Paragraph IV challenges affected etodolac?

A Paragraph IV certification is relevant only to a patent listed for an approved drug product and still capable of supporting an infringement action. A certification stating that a listed patent is invalid, unenforceable, or will not be infringed can trigger patent litigation and, in some circumstances, a 30-month stay of approval under the Hatch-Waxman Act.[3]

For U.S. Patent 4,966,768:

A historical Paragraph IV certification could have challenged the patent before expiration.
After expiration, the patent cannot create a new 30-month stay.
Any earlier litigation would be evaluated based on the law and patent status at the time of filing.
The patent's expired status removes it as a current barrier to an ANDA launch.

No current Paragraph IV risk can be inferred from this patent alone. A commercial launch analysis must examine all listed patents for the relevant reference product.

What patent landscape surrounds etodolac extended release?

The etodolac landscape has several distinct layers.

Active-ingredient patents

Etodolac is an established small-molecule NSAID. The basic compound and early therapeutic-use rights are historical and expired. They do not create current exclusivity.

Immediate-release formulation patents

Immediate-release etodolac tablets and capsules may have been protected by separate formulation or manufacturing patents. Those rights are distinct from the sustained-release matrix claimed in U.S. Patent 4,966,768.

Extended-release formulation patents

The '768 patent is directed to a specific matrix formulation. Other patents could cover:

Different HPMC grades;
Alternative hydrophilic polymers;
Coated pellets or beads;
Multiparticulate dosage forms;
Osmotic delivery systems;
Different buffer systems;
Enteric or delayed-release coatings;
Manufacturing processes; and
Alternative dissolution profiles.

A competitor using a different architecture would generally analyze those patent families separately rather than treating the '768 patent as a field-wide etodolac extended-release patent.

Method-of-use patents

The supplied claims are formulation claims. They do not claim a disease-treatment method, a dosing regimen, a patient population, or a specific clinical indication. A method-of-use patent would require separate claim language and a separate Orange Book assessment.

Manufacturing patents

The claims do not expressly require a particular granulation, milling, drying, blending, or compression process. A manufacturer could potentially practice the claimed composition using different manufacturing steps. Separate process patents could still create risk if they cover wet granulation, polymer distribution, tablet hardness, coating, or dissolution-control methods.

How strong is the patent estate for this technology?

The patent estate represented by U.S. Patent 4,966,768 was technically specific but commercially meaningful during its term.

Strength factor	Assessment
Claim breadth	Moderate to narrow
Structural specificity	High
Dependence on exact polymer grades	High
Dependence on dissolution performance	High
Design-around potential	Meaningful
Current enforceability	None because the patent expired
Historical value	Significant for a once-daily etodolac matrix product
Current commercial barrier	None from this patent

The claims are narrower than a broad claim to "an extended-release etodolac composition." The required HPMC chemistry, viscosity, molecular weight, ethylcellulose ratio, carrier-base percentage, buffer, and compressed-tablet format create multiple potential design-around routes.

During the patent term, however, the combination could have been difficult to avoid while preserving the same release profile and tablet architecture. A formulation developer seeking equivalent once-daily performance would have needed to change at least one material claim variable or adopt a distinct delivery system.

What generic launch risks exist today?

U.S. Patent 4,966,768 creates no current launch risk. The relevant risks for a new etodolac extended-release product are elsewhere:

Other unexpired formulation patents listed for the reference product.
Manufacturing patents covering granulation, compression, coating, or dissolution control.
FDA product-specific requirements for dissolution, bioequivalence, and pharmacokinetic performance.
Regulatory exclusivity associated with a newly approved product, if applicable.
Product liability and labeling obligations.
Freedom-to-operate issues outside the United States.

A generic developer using the same HPMC/ethylcellulose architecture is not blocked by the expired patent, but the patent's disclosure may remain relevant as prior art against later attempts to patent substantially similar formulations.

How does the U.S. position compare with international coverage?

A U.S. patent does not establish rights in Europe, Canada, Japan, China, or other jurisdictions. International protection would require corresponding national or regional patents, each with its own filing date, prosecution history, term, maintenance status, and claim scope.

For a global freedom-to-operate review, the relevant questions are:

Whether the priority application generated foreign counterparts;
Whether those counterparts were granted;
Whether they expired with the U.S. patent or on different dates;
Whether supplementary protection or other term adjustments applied;
Whether continuation, divisional, or national-phase claims remain active; and
Whether local regulatory exclusivity is independent of patent rights.

The expired U.S. patent should not be treated as evidence that every foreign counterpart has expired. Geographic coverage must be verified jurisdiction by jurisdiction through the relevant patent offices and family records.[1]

What licensing deals or settlement agreements are associated with the patent?

The supplied patent information does not establish a current licensing deal or settlement agreement. U.S. Patent 4,966,768 itself does not disclose commercial licenses, and a patent document cannot establish the full terms of a later private agreement.

For commercial diligence, relevant evidence would include:

ANDA litigation complaints and dismissals;
Consent judgments;
Settlement agreements filed under the Medicare Modernization Act;
FDA Paragraph IV litigation records;
SEC filings of publicly traded parties;
Assignment records; and
Royalty or supply agreements.

No current royalty obligation or settlement restriction should be inferred from the patent number alone.

Key Takeaways

U.S. Patent 4,966,768 claims a compressed, once-daily etodolac matrix dosage form.
The key technical combination is HPMC with tightly defined substitution, viscosity, and molecular-weight characteristics, combined with ethylcellulose and a buffer.
Claim 2 specifically requires dibasic sodium phosphate.
Claim 3 largely repeats the carrier-base percentage limitation in claim 1.
The patent issued on October 30, 1990, and its ordinary term expired on October 30, 2007.
The patent has no current blocking effect on generic etodolac development.
The claims are formulation-specific and provide several historical design-around paths.
Current market risk must be assessed against other listed patents, process patents, regulatory requirements, and foreign rights.
The patent does not itself claim a method of treatment, a disease indication, or a manufacturing process.

FAQs

Does U.S. Patent 4,966,768 cover all once-daily etodolac products?

No. It covers a specific polymer-matrix architecture with defined HPMC characteristics, ethylcellulose proportions, a carrier-base range, and a buffer-based release modifier.

Can a generic use HPMC in an extended-release etodolac tablet?

Yes. The patent is expired. During the patent term, a formulation using HPMC would have required analysis of the claimed viscosity, substitution profile, molecular weight, ethylcellulose ratio, carrier percentage, and release behavior.

Does claim 2 require dibasic sodium phosphate?

Yes. Claim 2 narrows claim 1 by expressly identifying dibasic sodium phosphate as the release-rate modifying agent.

Is an etodolac capsule outside the patent?

A capsule would have a strong argument that it does not satisfy the claim requirement for a "shaped and compressed" solid unit dosage form. The analysis would still depend on the actual dosage-form structure and any claim-construction or equivalence issues.

Can the expired patent be used as prior art against a new etodolac formulation patent?

Yes. An expired patent remains prior art. Its expiration removes enforceability, but it does not remove the disclosure from the prior-art record.

References

United States Patent and Trademark Office. (1990). U.S. Patent No. 4,966,768, sustained release dosage form containing etodolac. https://patents.google.com/patent/US4966768
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application submissions: Patent certification and 30-month stay provisions. https://www.fda.gov/drugs/abbreviated-new-drug-application-anda/anda-submissions-controls-and-certifications

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	62132	⤷ Start Trial
Australia	2215388	⤷ Start Trial
Australia	613663	⤷ Start Trial
Bulgaria	60697	⤷ Start Trial
Canada	1318600	⤷ Start Trial
Germany	3862272	⤷ Start Trial
Denmark	168421	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,966,768

Summary for Patent: 4,966,768