US Drug Patent 4,960,799: Claim Scope, Diclofenac Ophthalmic Formulation Coverage, and Patent Landscape

US Patent No. 4,960,799 covers a storage-stable, substantially isotonic aqueous ophthalmic solution containing diclofenac sodium or another pharmaceutically acceptable diclofenac salt, EDTA, a bacteriostat, and a solubilizer at specified concentrations and pH. The patent is a formulation and method-of-use patent, not a basic compound patent. Its 17-year patent term expired in 2007, eliminating current US patent exclusivity based on this patent. The covered product is associated with diclofenac sodium ophthalmic solution, historically marketed as Voltaren Ophthalmic.

What drug and formulation does US Patent 4,960,799 cover?

The claimed active ingredient is diclofenac, chemically described in the claims as ortho-(2,6-dichlorophenyl)aminophenylacetic acid. The principal commercial salt is diclofenac sodium.

Diclofenac is a nonsteroidal anti-inflammatory drug used in ophthalmology to treat postoperative ocular inflammation and related inflammatory conditions. The patent does not claim diclofenac as a chemical entity. It claims a particular aqueous ophthalmic delivery system intended to maintain stability, solubility, isotonicity, and antimicrobial protection.

The core formulation must contain:

Component	Claim 1 requirement
Diclofenac salt	About 0.1 to 5.0 mg/mL
EDTA salt	About 0.1 to 10 mg/mL
Bacteriostat	About 0.01 to 5 mg/mL
Solubilizer	About 0.5 to 200 mg/mL
Water	Remainder
pH	About 7.0 to 7.8
Physical property	Storage stable and substantially isotonic
Use	Treatment of ocular inflammation

Claim 2 narrows the diclofenac concentration to about 0.1 to 2.5 mg/mL. Claims 3 and 4 specify the sodium salt of diclofenac. Claim 5 specifies disodium EDTA, and claim 6 narrows the EDTA concentration to about 0.2 to 5 mg/mL.

What are the independent claims in US Patent 4,960,799?

The patent has two commercially relevant independent claims.

Claim 1: formulation claim

Claim 1 requires a storage-stable aqueous solution with all of the following limitations:

A pharmaceutically acceptable diclofenac salt.
A pH between about 7.0 and 7.8.
Substantially isotonicity.
EDTA or a pharmaceutically acceptable EDTA salt.
A bacteriostat.
A solubilizer.
Water as the remaining vehicle.
The specified concentration ranges for each ingredient.
Intended use for ocular inflammation.

The claim is cumulative. A competing product must satisfy each limitation, either literally or potentially under the doctrine of equivalents, to fall within the claim.

The formulation claim is materially narrower than a claim to all diclofenac eye drops. A product containing diclofenac sodium in an aqueous ophthalmic vehicle could avoid literal infringement if it lacks EDTA, uses a different preservative or solubilizer, falls outside the claimed pH or concentration ranges, or does not meet the claimed isotonicity and storage-stability requirements.

Claim 10: method-of-treatment claim

Claim 10 covers topical application to the eye of an effective amount of a solution according to claim 1 for treating or controlling ocular inflammation in a mammal.

Because claim 10 incorporates the limitations of claim 1, it does not independently cover every topical diclofenac ophthalmic treatment. The administered solution must still satisfy the formulation limitations in claim 1.

How do the dependent claims narrow the patent scope?

The dependent claims create specific embodiments within the broad formulation claim.

Claim	Added limitation
2	Diclofenac salt at about 0.1 to 2.5 mg/mL
3	Diclofenac salt is sodium diclofenac
4	Diclofenac sodium at about 0.1 to 2.5 mg/mL
5	EDTA component is disodium EDTA
6	EDTA at about 0.2 to 5 mg/mL
7	Bacteriostat selected from benzalkonium chloride, thimerosal, phenylethyl alcohol, methyl paraben, propyl paraben, chlorhexidine, or sorbic acid
8	Solubilizer is tris(hydroxymethyl)aminomethane, a polyethoxylated castor-oil ether, or a mixture
9	The claim 8 formulation uses sorbic acid as bacteriostat

The commercially important combination is likely represented by claims 4, 5, 6, 8, and 9: diclofenac sodium, disodium EDTA, a specified EDTA range, a specified solubilizer, and sorbic acid. The patent’s claim architecture indicates that the inventors were addressing formulation instability rather than discovering a new anti-inflammatory mechanism.

What technical problem does the patent address?

Diclofenac sodium presents formulation challenges in aqueous ophthalmic products. The formulation must balance:

Chemical stability during storage.
Adequate aqueous solubility.
Ocular tolerability.
Physiological tonicity.
Preservation against microbial contamination.
A pH compatible with stability and administration.

The patent uses EDTA as a chelating agent, a bacteriostat for antimicrobial protection, and a solubilizer to support the aqueous formulation. The pH range of about 7.0 to 7.8 is central to the claimed stability profile.

The claim does not require a particular container, dropper, dosing schedule, manufacturing process, particle size, viscosity, or ophthalmic device. It also does not expressly require a specific marketed concentration such as 0.1%, although the claimed concentration ranges encompass common diclofenac ophthalmic strengths.

What formulations are protected by US Patent 4,960,799?

The patent protects formulations that combine the required active ingredient, excipients, concentration ranges, pH, tonicity, and storage stability.

Diclofenac sodium formulations

Claims 3 and 4 specifically cover diclofenac sodium. A 0.1% solution contains approximately 1 mg/mL diclofenac sodium, which falls within both the broad range in claim 1 and the narrower range in claim 2.

A product containing approximately 1 mg/mL diclofenac sodium may therefore fall within the concentration limitations of claims 2, 3, and 4 if it also contains the required EDTA, bacteriostat, solubilizer, water, pH, isotonicity, and stability characteristics.

EDTA-containing formulations

Claims 1 and 5 require or specify an EDTA component. Claim 6 narrows the amount to about 0.2 to 5 mg/mL. Disodium EDTA is the specifically claimed salt in claim 5.

A formulation using a different chelating agent, such as citrate or another metal-ion control system, would not literally satisfy the EDTA limitation. The infringement analysis would depend on the claim construction, technical function, prosecution history, and equivalence arguments.

Preserved formulations

Claim 7 identifies seven classes or substances that can satisfy the bacteriostat limitation. Claim 9 creates a more specific embodiment using sorbic acid with the claim 8 solubilizers.

The list limits the dependent claim but does not necessarily limit claim 1 to those seven preservatives. Claim 1 uses the broader phrase "pharmaceutically acceptable bacteriostat." A different preservative could potentially fall within claim 1 if it meets the broader limitation, subject to claim construction and validity analysis.

Solubilized formulations

Claim 8 identifies tris(hydroxymethyl)aminomethane, commonly called tromethamine or TRIS, and polyethoxylated ethers of castor oil. The use of one of these solubilizers strengthens the literal infringement case under claim 8 where the remaining limitations are present.

A product formulated as a suspension, emulsion, gel, ointment, or anhydrous dosage form would generally fall outside the express aqueous-solution limitation of claim 1, although a separate patent could cover such alternatives.

When did US Patent 4,960,799 lose exclusivity?

US Patent 4,960,799 issued on November 27, 1990. For a US utility patent filed before June 8, 1995, the applicable term generally was 17 years from grant, subject to applicable patent-term adjustments, terminal disclaimers, and regulatory extensions. On that basis, the patent expired on November 27, 2007. [1]

The patent therefore has no enforceable ordinary patent term in the United States. Patent expiration is distinct from FDA approval status. A product can remain FDA-approved after the formulation patent expires, and generic manufacturers can rely on the abbreviated new drug application pathway once applicable patent and regulatory barriers are removed.

What was the Orange Book status of the diclofenac ophthalmic product?

The relevant branded product was Voltaren Ophthalmic, a diclofenac sodium ophthalmic solution generally marketed at 0.1%. FDA product information identifies diclofenac sodium ophthalmic solution as an approved ophthalmic NSAID product. [2]

The Orange Book historically listed patent information for approved drug products, including patents submitted by the NDA holder. Patent No. 4,960,799 was associated with the formulation protection for diclofenac ophthalmic solution in the US regulatory record. The listing did not transform the patent into a compound patent or expand its claims beyond the issued language.

Because the patent expired in 2007, it no longer creates an Orange Book patent block against an ANDA applicant. FDA Orange Book listings and patent certifications remain relevant to historical generic-entry timing, but they do not revive an expired patent. [3]

Were Paragraph IV challenges relevant to this patent?

Paragraph IV certifications are used when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or will not be infringed. Before expiration, an applicant seeking approval of a diclofenac sodium ophthalmic generic could have faced a Paragraph IV certification against US 4,960,799 if the patent was listed for the reference product.

The principal legal consequences would have included:

Notice to the patent owner and NDA holder.
Potential patent litigation within 45 days.
A possible 30-month FDA approval stay under Hatch-Waxman.
A potential 180-day first-applicant exclusivity period if statutory requirements were met.

Those consequences were time-limited. An ANDA submitted after patent expiration generally could rely on a certification reflecting expiration rather than mount a current Paragraph IV challenge. The patent’s expiration means that no current ANDA applicant needs to defeat this patent to launch a non-infringing diclofenac ophthalmic product.

No continuing Paragraph IV barrier arises from US 4,960,799 alone. Current risk must instead be assessed against later patents, product-specific patents, regulatory exclusivity, and non-patent requirements.

What patent litigation affected US Patent 4,960,799?

The principal litigation risk associated with the patent would have been generic entry into diclofenac sodium ophthalmic solution before its 2007 expiration. Public patent records identify the patent as an expired formulation patent associated with diclofenac ophthalmic products. [1]

The patent’s current litigation value is zero as an enforcement asset because an expired patent cannot support a new infringement action for post-expiration conduct. Historical litigation involving diclofenac ophthalmic products, if any, must be separated from current freedom-to-operate analysis. A settlement agreement reached before expiration could affect historical launch timing, but it would not extend the patent term or bind unrelated parties after expiration absent separate contractual obligations.

Which companies challenged diclofenac ophthalmic exclusivity?

The market included generic manufacturers of diclofenac sodium ophthalmic solution after the branded product’s patent protection expired. FDA approval records identify multiple approved diclofenac ophthalmic products and applicants over time, while product availability has changed through acquisitions, discontinuations, and manufacturer portfolio changes. [2][4]

The expired status of US 4,960,799 makes the identity of a historical Paragraph IV challenger less important for current commercial analysis. The relevant question today is whether a proposed product meets the FDA’s therapeutic-equivalence and quality requirements and whether it infringes any later, unexpired patents.

How strong was the patent estate for diclofenac ophthalmic solution?

The strength of US 4,960,799 was moderate as a formulation patent during its term and weak as a long-term exclusivity platform.

Strengths

It covered a complete aqueous ophthalmic composition rather than a single excipient.
It included pH, tonicity, storage stability, concentration, preservative, and solubilizer limitations.
Claims 3 through 9 created narrower fallback positions.
The claim set targeted the formulation architecture likely used in the commercial product.

Weaknesses

It did not cover diclofenac itself.
It did not cover every diclofenac ophthalmic formulation.
Several limitations were functional or approximate, including "storage stable," "substantially isotonic," and "about."
A competitor could potentially design around the EDTA, preservative, solubilizer, pH, or dosage-form limitations.
The patent expired in 2007.

The patent was therefore capable of delaying a close formulation copy but was not a durable barrier against alternative diclofenac ophthalmic formulations.

What generic launch risks exist after patent expiration?

Current generic launch risk from US 4,960,799 is minimal. The patent no longer blocks approval or commercial manufacture.

A modern applicant would still face the following non-patent issues:

Risk area	Current significance
FDA ANDA approval	Requires pharmaceutical equivalence, bioequivalence or applicable waiver, quality data, and manufacturing compliance
Product sameness	The applicant must satisfy the applicable ophthalmic solution standards
Preservative and excipient safety	Excipients must be acceptable for the proposed route and concentration
Sterility	Ophthalmic products require validated sterile manufacturing and container closure controls
Later patents	Requires a current patent search separate from US 4,960,799
Trademark and trade dress	Brand identifiers remain separate from patent rights
Supply chain	Sterile ophthalmic manufacturing capacity can constrain launch
Commercial pricing	Multiple generic suppliers can compress price and margins

A generic using the same general composition could launch after satisfying FDA requirements without obtaining a license under this expired patent.

How does US Patent 4,960,799 compare with compound and method-of-use patents?

US 4,960,799 is narrower than a compound patent and broader than a single manufacturing example.

Patent type	Scope relative to US 4,960,799
Diclofenac compound patent	Potentially covers the active molecule across formulations and indications
Diclofenac sodium salt patent	Covers the salt or its preparation, depending on claim language
Formulation patent	Covers specified composition and physical properties
Method-of-use patent	Covers treatment of a defined condition or patient population
Manufacturing patent	Covers synthesis, purification, sterilization, filling, or packaging
Device patent	Covers the dropper, container, closure, or delivery mechanism

The patent’s claim 10 is a method-of-use claim, but it is dependent in substance on the composition of claim 1. It does not independently create broad protection for topical diclofenac treatment.

Does US Patent 4,960,799 create biosimilar risk?

No. Diclofenac sodium is a small-molecule drug, not a biologic. Biosimilar procedures under the Public Health Service Act do not apply. Generic competition proceeds through the FDA’s ANDA pathway under section 505(j) of the Federal Food, Drug, and Cosmetic Act. [3]

The relevant competitive threats are generic ophthalmic solutions, not biosimilars.

What manufacturing and intellectual-property barriers remain?

The expired patent does not prevent manufacture of the covered solution. Practical barriers remain in sterile ophthalmic production, including:

Sterile filtration or aseptic processing.
Validated preservative effectiveness.
Container-closure integrity.
Control of particulate matter and extractables.
Consistent pH and osmolality.
Stability testing in the proposed package.
Reliable supply of ophthalmic-grade excipients.
FDA inspection readiness.

A manufacturer also must review later patents covering packaging, preservative systems, manufacturing processes, delivery devices, or new indications. Those rights are legally separate from US 4,960,799.

What is the geographic coverage of US Patent 4,960,799?

The patent’s rights were limited to the United States. Foreign counterparts, if filed, would have had separate national rights, terms, prosecution histories, and expiration dates. US expiration did not automatically terminate foreign patents.

For international commercialization, the relevant analysis must be performed country by country, including review of:

National patent family members.
Patent-term adjustments or supplementary protection certificates.
Regulatory exclusivity.
Local Orange Book equivalents.
National litigation and settlement records.
Local product approvals and market authorization status.

The US patent cannot be used to block an overseas product after US expiration.

Key Takeaways

US Patent 4,960,799 covers a storage-stable, substantially isotonic aqueous diclofenac ophthalmic solution.
Claim 1 requires diclofenac salt, EDTA, a bacteriostat, a solubilizer, water, specified concentration ranges, and a pH of about 7.0 to 7.8.
Claims 3 and 4 specifically target diclofenac sodium, while claims 5 through 9 narrow the EDTA, preservative, and solubilizer combinations.
Claim 10 covers topical ocular treatment using the claimed formulation.
The patent is a formulation patent, not a basic diclofenac compound patent.
Its US patent term expired on November 27, 2007.
The expired patent no longer creates a current Paragraph IV, Orange Book, or launch barrier.
Diclofenac sodium ophthalmic products compete through the generic ANDA pathway, not the biosimilar pathway.
Current freedom-to-operate work should focus on later patents, manufacturing processes, packaging, delivery devices, trademarks, and FDA requirements.
The patent had meaningful blocking value against close formulation copies during its term but limited scope against alternative diclofenac ophthalmic formulations.

FAQs

Can a generic use the same diclofenac sodium ophthalmic formulation after 2007?

Yes. Expiration of US Patent 4,960,799 removes the patent restriction, although the product still must satisfy FDA approval, sterility, quality, labeling, and manufacturing requirements.

Does the patent cover diclofenac tablets or injectable diclofenac?

No. The claims are directed to aqueous ophthalmic solutions and topical treatment of ocular inflammation. They do not cover unrelated dosage forms.

Would a diclofenac eye drop without EDTA avoid the patent?

It would not literally meet the EDTA limitation in claim 1. A complete infringement analysis would still require review of claim construction and possible equivalents.

Is Voltaren Ophthalmic protected by an active US patent today?

US Patent 4,960,799 is expired. Any current US protection would have to arise from a separate unexpired patent, regulatory exclusivity, trademark rights, or other legal rights.

Can a manufacturer market a diclofenac ophthalmic solution outside the United States?

US Patent 4,960,799 does not control foreign markets. The manufacturer must separately review patent-family members, regulatory approvals, and local exclusivity in each jurisdiction.

References

United States Patent and Trademark Office. (1990). Stable aqueous compositions of diclofenac salts for ophthalmic use, U.S. Patent No. 4,960,799.
U.S. Food and Drug Administration. (n.d.). Diclofenac sodium ophthalmic solution prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
U.S. Food and Drug Administration. (n.d.). Drugs@FDA: FDA-approved drugs database.

Details for Patent: 4,960,799

Summary for Patent: 4,960,799