# United States Drug Patent 6,974,595: Claim Scope, Expiration, Orange Book Status, and Diclofenac Patent Landscape

US Patent 6,974,595 protects certain orally administered diclofenac formulations designed to produce rapid and relatively consistent absorption. The core technical concept is a diclofenac formulation, particularly diclofenac potassium, combined with an alkalinizing agent such as sodium bicarbonate or potassium bicarbonate. The claims also cover powder-for-solution products and the fast-release layer of a two-layer tablet.

The patent is a small-molecule formulation patent, not a compound patent. Its commercial relevance depends on whether a competing product practices the claimed formulation, dosage form, alkalinizer concentration, and pharmacokinetic limitations. The patent has expired, so it does not currently block generic or competing diclofenac products in the United States.

What does United States Patent 6,974,595 protect?

The patent protects methods of administering diclofenac to achieve rapid absorption, measured principally by time to maximum plasma concentration, or Tmax.

The claim set has four independent claims:

Independent claim	Protected subject matter	Principal limitations
Claim 1	Method for obtaining rapid and consistent diclofenac absorption	Tmax of 5-30 minutes, CV below about 70%, diclofenac plus sodium or potassium bicarbonate, bicarbonate at about 20-80% by diclofenac weight, flavoring, powder-for-solution or fast layer of a bilayer tablet
Claim 14	Method of treating a patient with diclofenac	Diclofenac plus alkali-metal carbonate or bicarbonate at more than about 20% by diclofenac weight; powder or fast layer
Claim 28	Method for obtaining rapid diclofenac absorption	Tmax of 5-30 minutes; powder-for-solution or fast layer of a bilayer tablet
Claim 34	Method for obtaining rapid absorption using an absorption-enhancing mechanism	Tmax of 5-30 minutes; formulation includes diclofenac and a means for enhancing Tmax; powder or fast layer

The patent therefore has two principal claim groups:

Claims directed to rapid pharmacokinetics.
Claims directed to the formulation mechanism, particularly alkalinization.

The broadest independent claim from a formulation perspective is claim 28 because it does not expressly require bicarbonate, carbonate, flavoring, a specific salt, or a defined alkalinizer concentration. It still requires the accused product to be a powder dissolved or dispersed in water or the fast-release layer of a two-layer tablet, and it requires the claimed Tmax result.

Claim 14 is broader regarding the type of alkalinizing agent because it covers alkali-metal carbonates or bicarbonates. Claim 1 is narrower because it limits the agent to sodium bicarbonate, potassium bicarbonate, or mixtures and adds flavoring and the CV limitation.

How are the claims structured?

Claim 1: rapid and consistent Tmax with bicarbonate

Claim 1 requires all of the following:

Oral administration to a human patient.
Diclofenac in acid and/or salt form.
Sodium bicarbonate, potassium bicarbonate, or both.
Bicarbonate at approximately 20-80% by weight relative to diclofenac.
Mint, aniseed, ammonium glycyrrhizinate, or a combination as a flavoring substance.
A powder dissolved or dispersed in water, or a fast-release layer in a two-layer tablet.
Average Tmax between 5 and 30 minutes.
Tmax coefficient of variation below about 70%.

This is a cumulative method claim. A product that lacks the required flavoring limitation may avoid claim 1 even if it contains diclofenac potassium and potassium bicarbonate.

Claim 14: treatment claim with carbonate or bicarbonate

Claim 14 omits the flavoring requirement and does not require a specific Tmax in the independent claim. It requires:

Treatment of a human patient with diclofenac.
Diclofenac in acid or salt form.
One or more alkali-metal carbonates or bicarbonates.
The carbonate or bicarbonate at more than about 20% by weight relative to diclofenac.
A powder formulation for dispersion or dissolution in water, or a fast-release layer in a bilayer tablet.

This claim is potentially broader than claim 1 for products containing carbonate or bicarbonate. It is narrower in requiring an alkali-metal carbonate or bicarbonate and one of the two specified dosage-form architectures.

Claim 28: formulation and Tmax without an alkalinizer

Claim 28 is the most important claim for an infringement analysis involving a rapid diclofenac powder or bilayer tablet. It does not require an alkalinizing agent. Its key limitations are:

Oral administration.
Diclofenac in acid and/or salt form.
Tmax between 5 and 30 minutes.
Powder dissolved or dispersed in water, or a fast-release layer of a two-layer tablet.

The absence of a bicarbonate requirement gives claim 28 a wider theoretical formulation scope than claims 1 and 14. The claim remains dependent on the specified dosage form and demonstrated pharmacokinetic result.

Claim 34: “means for enhancing” Tmax

Claim 34 requires diclofenac and “means for enhancing” average Tmax. The language may be treated as a means-plus-function limitation under 35 U.S.C. §112(f), depending on claim construction. If so, the relevant structure would be limited to structures disclosed in the specification and their statutory equivalents, rather than every possible technology that accelerates diclofenac absorption.

Claim 38 identifies alkali-metal carbonates or bicarbonates as the enhancing means. Claims 39-41 further narrow the scope to a 20-80% weight range and sodium or potassium bicarbonate.

What formulations are protected by US 6,974,595?

The patent covers two dosage-form categories.

Powder formulation dissolved or dispersed in water

The claims cover a powder containing diclofenac that is dissolved or dispersed in water before oral administration. The claim language is consistent with a sachet or other reconstituted oral solution or suspension.

A representative formulation within the claim set contains:

Approximately 50 mg diclofenac potassium.
Approximately 22-24 mg potassium bicarbonate.
A flavoring agent such as mint, aniseed, or ammonium glycyrrhizinate.
Powder intended for dissolution or dispersion in water.

The claims do not require that every excipient be disclosed in the claim. The infringement analysis would focus on the active ingredient, alkalinizer, relative concentration, dosage form, and pharmacokinetic outcome.

Fast-release layer in a bilayer tablet

The patent also covers a two-layer tablet containing:

A fast-release layer.
A slow-release layer.

Claim 11 identifies a specific example:

Approximately 15 mg diclofenac potassium in the fast-release layer.
Approximately 70 mg diclofenac potassium in the slow-release layer.

Claims 9, 24, 33 and 43 separately identify the fast-release layer as the claimed diclofenac formulation. A conventional immediate-release tablet without a separate slow-release layer is outside these dosage-form limitations, although it could still raise issues under a different claim if the claim language and product structure are satisfied.

What are the key dependent claim limitations?

Claims	Limitation
2, 30, 36	Tmax of 13-27 minutes
3, 20	Bicarbonate or carbonate at approximately 40-80% by diclofenac weight
4, 18	10-60 mg diclofenac potassium
5, 19	10-60 mg diclofenac sodium
6, 21, 40	Sodium bicarbonate
7, 22, 41	Potassium bicarbonate
8, 23, 32, 42	Powder formulation
9, 24, 33, 43	Fast-release layer
10, 25	Approximately 50 mg diclofenac potassium in powder formulation
11, 26	15 mg fast-release layer and 70 mg slow-release layer
12, 27	50 mg diclofenac potassium plus 22-24 mg potassium bicarbonate
13, 17, 31, 37	Average Cmax of 1,700-2,300 ng/mL for approximately 50 mg diclofenac
15, 16, 29, 35	Tmax of 5-30 minutes, with claim 16, 29 and 35 adding CV below about 70%
38	Carbonates or bicarbonates as the Tmax-enhancing means
39	Carbonates or bicarbonates at 20-80% by diclofenac weight

The Cmax limitations are pharmacokinetic limitations. They may require clinical or bioequivalence data to establish infringement. A formulation could satisfy the structural limitations but avoid a Cmax-dependent claim if the measured Cmax falls outside the claimed range.

When did US Patent 6,974,595 expire?

US Patent 6,974,595 was issued on December 13, 2005. Its enforceable term was governed by the Uruguay Round Agreements Act patent-term rules, generally providing a term of 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, and any terminal disclaimer recorded in the prosecution history.[1]

The patent is expired as of the current date. It therefore does not create a live United States patent barrier to generic entry or development of competing diclofenac products.

Expiration of the patent does not eliminate other possible rights, including:

Later-issued formulation patents.
Patents covering a specific commercial product.
Regulatory exclusivity.
Trademark rights.
Trade secrets relating to manufacturing.
Patent rights in countries where corresponding family members had different terms or status.

What is the Orange Book status of US 6,974,595?

The patent is not a currently enforceable Orange Book barrier because it has expired. Orange Book relevance depends on whether the patent was listed against a specific approved drug application and whether the patent remains unexpired.[2]

For a generic applicant, an expired patent does not support a current Paragraph IV certification as an actionable patent challenge. The practical regulatory position is generally:

A listed expired patent does not prevent ANDA approval.
No 30-month stay can be generated from an expired patent.
The patent cannot support a present injunction against generic launch.
Any product-specific listing must be reviewed in the current FDA Orange Book and applicable NDA records.

The patent’s claim language is relevant to formulation design and historical product protection, but the patent itself is no longer a live Orange Book exclusivity asset.

Are Paragraph IV challenges or litigation associated with this patent still relevant?

No live Paragraph IV risk attaches to an expired US Patent 6,974,595. A Paragraph IV certification is principally relevant when a listed patent is unexpired and an ANDA applicant asserts that the patent is invalid, unenforceable, or not infringed.[3]

Historical litigation or settlement agreements could still matter for:

Damages exposure during the pre-expiration period.
Launch dates agreed by generic companies.
Admissions concerning claim construction.
Validity positions involving rapid-release diclofenac formulations.
Family-member disputes in other jurisdictions.

The supplied claim set does not identify any litigation, settlement, or license agreement. Patent status, litigation history, and settlement terms should be distinguished from the technical scope of the claims.

Which products are most closely related to the claimed technology?

The closest commercial analogue is a rapidly absorbed diclofenac potassium powder for oral solution, particularly a product containing approximately 50 mg diclofenac potassium and an alkalinizing excipient. The FDA-approved product Cambia is a 50 mg diclofenac potassium powder for oral solution and is administered after dissolution in water.[4]

The comparison is technically relevant because the patent specifically claims:

50 mg diclofenac potassium.
Powder dissolved or dispersed in water.
Rapid Tmax.
Carbonate or bicarbonate-based absorption enhancement.
Potassium bicarbonate quantities in the approximate 22-24 mg range.

The existence of a similar approved product does not, by itself, establish that every product detail falls within every claim. Product labeling, regulatory submissions, formulation composition, and pharmacokinetic data must be compared claim by claim.

How does this patent compare with conventional diclofenac products?

Product category	Likely relationship to US 6,974,595
Standard diclofenac sodium delayed-release tablet	Generally outside the claimed powder and bilayer fast-layer limitations
Conventional diclofenac potassium immediate-release tablet	May avoid the claimed dosage form, but a product-specific analysis is required
Diclofenac potassium powder for oral solution	Closest technical category
Diclofenac sodium powder for solution	Potentially relevant under claims 5, 14, 19, 28 and 34, depending on all limitations
Two-layer immediate-release/sustained-release tablet	Potentially within claims 1, 9, 11, 14, 24, 26, 28, 33 and 43
Topical diclofenac gel or patch	Outside the oral-administration limitations
Injectable diclofenac	Outside the oral-administration limitations
Diclofenac product using non-alkali-metal absorption technology	May avoid claims requiring carbonate or bicarbonate, but claim 28 is broader

The patent does not cover diclofenac as a chemical entity. It also does not cover every oral diclofenac product. Its strongest historical position was against oral products combining rapid-release architecture with the claimed performance characteristics.

What generic entry risks exist?

For this patent alone, current generic entry risk is low because the patent has expired. Historical risk was highest for an ANDA or NDA product that used:

Diclofenac potassium powder for oral solution.
Approximately 50 mg diclofenac potassium.
Potassium or sodium bicarbonate.
A bicarbonate concentration above 20% by weight relative to diclofenac.
A Tmax between 5 and 30 minutes.
A fast-release layer in a bilayer tablet.
The claimed Cmax or Tmax variability.

Potential design-around strategies during the patent term included:

Using a conventional tablet rather than a powder-for-solution product.
Avoiding a two-layer tablet with a separately identifiable fast-release layer.
Using an absorption enhancer other than an alkali-metal carbonate or bicarbonate.
Reducing the carbonate or bicarbonate concentration below the claimed threshold.
Using a different release profile that does not produce the claimed Tmax.
Developing a non-oral dosage form.
Avoiding the claimed diclofenac dose or pharmacokinetic range.

Because claims 28 and 34 contain functional pharmacokinetic limitations without an express bicarbonate requirement, a design-around based solely on removing bicarbonate would not necessarily avoid all claims.

How strong is the patent estate for rapid-release diclofenac?

The patent’s historical strength was moderate for a narrow product category and weaker for broad market control.

Strengths

Multiple independent method claims.
Coverage of both powder-for-solution and bilayer tablet formats.
Specific protection for diclofenac potassium.
Pharmacokinetic endpoints tied to rapid onset.
Alternative claim theories based on treatment, Tmax, and absorption enhancement.
Dependent claims covering commercially plausible 50 mg products.

Vulnerabilities

The claims are method claims rather than composition claims.
Several limitations depend on clinical pharmacokinetic measurements.
Tmax and CV can vary with food, patient population, study design, and sampling schedule.
The claims require particular dosage-form structures.
Claim 34 may raise means-plus-function construction issues.
Functional-result claims can create proof and enablement disputes.
The patent is expired, eliminating present enforcement value.

The patent had meaningful relevance to rapid diclofenac powder products but did not create a broad monopoly over oral diclofenac.

Does biosimilar risk apply to this patent?

No. Diclofenac is a chemically synthesized small-molecule active pharmaceutical ingredient. Competing products proceed through the generic drug pathway, principally an ANDA under section 505(j) of the Federal Food, Drug, and Cosmetic Act, rather than the biosimilar pathway under section 351(k) of the Public Health Service Act.

The relevant competitive risks are generic substitution, formulation development, bioequivalence, Orange Book certifications, and product-specific patents. Biosimilar interchangeability and biologic reference-product exclusivity are not applicable.

What is the geographic coverage of this patent?

US Patent 6,974,595 covers only the United States. Corresponding international applications may have produced patents in Europe, Canada, Australia, or other jurisdictions, but each family member has its own:

Claim scope.
Filing and priority dates.
Prosecution history.
Patent-term calculation.
Expiration date.
Opposition or litigation record.
Status.

US expiration does not establish that every foreign counterpart has expired. Companies evaluating international launch should review the complete patent family and national registers separately.

What manufacturing and intellectual-property barriers remain?

The expired patent does not prevent manufacture of a formulation that falls within its claims. Residual barriers may include:

Reproducible powder dispersion in water.
Taste masking and reduction of diclofenac astringency.
Control of bicarbonate content and pH.
Stability of diclofenac potassium in the finished product.
Consistent dissolution and absorption.
Bioequivalence against the relevant reference product.
Later patents covering excipient systems, packaging, manufacturing processes, or specific release technologies.
Regulatory requirements for an ANDA or 505(b)(2) application.

The flavoring limitations in claim 1 reflect a product-development issue as well as a patent limitation. Mint, aniseed, and ammonium glycyrrhizinate are claimed for palatability and astringency control, but their use alone does not establish infringement without the other limitations.

Key Takeaways

US Patent 6,974,595 is a formulation and method-of-use patent for rapidly absorbed oral diclofenac.
Its principal technology combines diclofenac, rapid-release dosage architecture, and pharmacokinetic performance.
Claims 1 and 14 focus on alkali-metal bicarbonates or carbonates.
Claim 28 is the broadest independent claim for powder or bilayer formulations because it does not expressly require bicarbonate.
Claim 34 uses “means for enhancing” language that may create a means-plus-function construction issue.
The patent covers powder-for-solution products and fast-release layers in bilayer tablets, not all oral diclofenac products.
The patent is expired and does not create a current US generic-entry block.
Diclofenac is a small molecule, so biosimilar analysis is not applicable.
Current diligence should focus on later product-specific patents, Orange Book listings, regulatory exclusivity, and foreign family members.

FAQs

Can a generic company launch a diclofenac potassium powder after expiration of US 6,974,595?

Yes, expiration of this patent removes its US patent barrier. The applicant must still satisfy FDA requirements and address any other unexpired patents or regulatory exclusivities.

Does using sodium bicarbonate automatically infringe the patent?

No. Sodium bicarbonate is only one limitation in certain claims. Infringement would require satisfaction of all limitations, including dosage form, oral administration, diclofenac form, concentration, and any applicable Tmax or Cmax requirement.

Does a 50 mg diclofenac potassium tablet fall within the patent?

Not necessarily. The claims emphasize a powder dissolved or dispersed in water and a fast-release layer in a two-layer tablet. A conventional single-layer tablet may avoid those dosage-form limitations.

Are Tmax and Cmax limitations evaluated from the product label?

Usually not by label review alone. These are pharmacokinetic limitations that may require clinical study data, regulatory submissions, or other technical evidence.

Can a foreign patent family member still block diclofenac powder commercialization?

Yes. US expiration has no automatic effect on foreign patents. Each national family member must be reviewed independently for scope, term, validity, and enforcement status.

References

United States Patent and Trademark Office. (2005). U.S. Patent No. 6,974,595, Diclofenac formulation and method of administration.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (2024). Abbreviated new drug application regulations and patent certification requirements.
U.S. Food and Drug Administration. (2024). Cambia (diclofenac potassium) for oral solution prescribing information.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Italy	MI96A0992	May 17, 1996

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Argentina	007165	⤷ Start Trial
Austria	210976	⤷ Start Trial
Austria	229801	⤷ Start Trial
Australia	3167697	⤷ Start Trial
Australia	733083	⤷ Start Trial
Canada	2254144	⤷ Start Trial
Germany	69709349	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,974,595

Summary for Patent: 6,974,595