United States Patent 7,939,518: Scope, Claims, Expiration and Diclofenac Potassium Patent Landscape

US Patent 7,939,518 protects a treatment protocol for acute post-osteotomy pain using 13 to 30 mg of diclofenac potassium in a dispersible liquid formulation, administered orally at defined intervals and at no more than 100 mg per day. The strongest commercial embodiment is 25 mg administered four times over 24 hours, corresponding to the Zipsor diclofenac potassium liquid-filled capsule product.

The patent is primarily a method-of-use patent. Its enforceability depends on proving the full dosing regimen, formulation, surgical indication and, for narrower claims, pharmacokinetic or clinical-performance limitations. It does not broadly cover diclofenac potassium, all oral diclofenac products, or every use of a liquid diclofenac formulation.

What drug and product does US Patent 7,939,518 protect?

US 7,939,518 is directed to diclofenac potassium administered in a dispersible liquid formulation for acute pain after osteotomy, particularly bunionectomy. The commercial product most closely associated with the claims is Zipsor, a 25 mg diclofenac potassium liquid-filled capsule marketed for the relief of mild to moderate acute pain in adults.

Field	Patent scope
Active ingredient	Diclofenac potassium
Dosage form	Dispersible liquid formulation, including a capsule
Core dose	About 13 to 30 mg per administration
Dosing interval	About every 4 to 8 hours
Daily maximum	No more than about 100 mg
Primary indication	Acute post-osteotomy pain
Surgical subtype	Correction of a bone deformity; dependent claim specifies bunionectomy
Treatment duration	At least 24 hours, with dependent claims extending to seven days
Key commercial dose	25 mg
Key commercial regimen	25 mg four times in approximately 24 hours
Product association	Zipsor diclofenac potassium liquid-filled capsule

The FDA-approved Zipsor label describes a 25 mg diclofenac potassium liquid-filled capsule administered four times daily for acute pain. The labeled maximum is 100 mg per day.[1]

What does independent claim 1 require?

Claim 1 has several cumulative limitations. A potentially infringing method must satisfy each material element:

The patient must require treatment for acute post-osteotomy pain.
The osteotomy must be correction of a bone deformity.
Diclofenac potassium must be administered orally.
The drug must be delivered in a dispersible liquid formulation.
Each dose must be between about 13 and 30 mg.
Dosing must occur approximately every 4 to 8 hours.
Treatment must continue for at least 24 hours.
The total daily amount must not exceed approximately 100 mg.

A product using the same ingredient and dose but administered for dental pain, menstrual pain, ordinary postoperative pain without an osteotomy, or chronic arthritis would not necessarily fall within claim 1. Likewise, an immediate-release tablet rather than the claimed dispersible liquid formulation would present a non-infringement position unless the tablet legally meets the formulation limitation.

The claim is therefore narrower than a composition patent. It does not prevent all competitors from manufacturing or selling diclofenac potassium. It targets use of a particular dosage form under a particular dosing protocol for a defined surgical pain population.

How do claims 2 through 8 narrow the patent?

Claims 2 through 8 add surgical, scheduling, duration and efficacy limitations.

Claim	Added limitation	Commercial or litigation significance
2	Osteotomy is a bunionectomy	Narrows the claim to a common bone-deformity procedure
3	Dosing every 5 to 8 hours	Excludes some four-hour regimens
4	Dosing about every 6 hours	Targets a specific interval
5	Treatment for at least about 30 hours	Extends beyond the minimum 24-hour period
6	Treatment for 48 hours through seven days	Defines longer postoperative courses
7	Dose selected from specified amounts, including 25 mg	Creates dose-specific fallback positions
8	Effectiveness for approximately 6 to 8 hours	Adds a duration-of-analgesia limitation

Claim 2 is commercially important because it links the patent to bunionectomy, a procedure used in clinical trials for acute postoperative pain. Claims 3, 4 and 17 create potential coverage around four-times-daily or approximately six-hour dosing.

Claim 7 is drafted as a list of specific dose values. It supplies narrower positions if the broader 13 to 30 mg range is challenged. The list includes 25 mg, the dose most closely associated with Zipsor.

What pharmacokinetic limitations are covered by claims 9 through 11?

Claims 9 through 11 protect pharmacokinetic characteristics associated with rapid absorption and elimination:

Claim 9 requires plasma diclofenac concentrations of approximately 670 to 1,500 ng/mL in less than 30 minutes, with onset of pain relief.
Claim 10 requires an immediate increase in plasma concentration with a T(max) of approximately 0.47 hours.
Claim 11 requires diclofenac potassium to be substantially eliminated from plasma during the first two hours after administration.

These claims are difficult to assess from product labeling alone. Infringement analysis would likely require comparative pharmacokinetic testing under defined conditions. The claims also raise construction issues concerning:

The meaning of "less than about 30 minutes."
Whether the plasma range must be reached in every patient or is an average result.
Whether "T(max) of about 0.47 hours" permits a clinically meaningful range.
The meaning of "substantially eliminated."
Whether the measured concentration must result from the claimed dose and formulation.

A generic applicant could attempt to design around these limitations by changing liquid composition, absorption characteristics or release behavior. That strategy would not necessarily avoid claims 1 through 8, which are principally defined by indication, dose, formulation, interval and duration.

What clinical-performance limitations are covered by claims 12 through 17?

Claims 12 through 17 concentrate on a 25 mg regimen and clinical trial outcomes.

Claim	Limitation
12	Approximately 25 mg of diclofenac potassium
13	Average 48-hour NPRS pain score of approximately 2.49
14	Median time to at least 30% pain reduction of approximately 60 minutes
15	Median time to meaningful pain relief of approximately 70 minutes
16	Clinically significant analgesic efficacy for approximately six hours
17	25 mg administered four times over approximately 24 hours

Claim 17 is likely the most commercially relevant of these dependent claims. It corresponds closely to the labeled 25 mg, four-times-daily regimen.

Claims 13 through 16 are narrower and may be difficult to enforce without evidence that the accused product, when used as claimed, produces the specified outcomes. Clinical-result limitations can also generate disputes over patient population, statistical analysis, endpoint definitions and whether the limitation is a true method step or an intended result.

What formulation is protected by US 7,939,518?

The patent protects use of diclofenac potassium in a "dispersible liquid formulation." Claim 18 confirms that the formulation may be contained in a capsule.

The formulation limitation distinguishes the claimed product from conventional diclofenac potassium tablets. A liquid-filled capsule can provide rapid dispersion and absorption after oral administration. The patent does not, based on the supplied claims, require a specific excipient, capsule shell, particle size, solvent system or manufacturing process.

That distinction matters. A competitor may avoid the patent by using:

A conventional solid tablet.
A powder-filled capsule.
A different diclofenac salt.
A non-dispersible modified-release dosage form.
A liquid formulation used outside the claimed clinical and dosing conditions.

The formulation limitation also creates an infringement risk for an equivalent liquid-filled capsule even if the capsule has a different trade name. A change in excipients alone may not avoid infringement if the accused product remains a dispersible liquid formulation under the proper claim construction.

Does the patent cover all diclofenac products?

No. US 7,939,518 does not claim:

Diclofenac as a chemical compound.
All diclofenac potassium formulations.
Diclofenac sodium products.
Topical diclofenac.
Injectable diclofenac.
Extended-release diclofenac.
All acute pain treatment.
Every postoperative pain indication.
Every bunionectomy analgesic regimen.

The patent covers a specific use of a specific diclofenac salt in a specific formulation and dose range. Its commercial value depends on the extent to which a competitor seeks to replicate the rapid-onset liquid formulation and the 25 mg, four-times-daily dosing protocol.

When does US Patent 7,939,518 lose exclusivity?

The patent term is governed principally by the 20-year term measured from the applicable earliest nonprovisional filing date, subject to patent-term adjustment, patent-term extension and any terminal disclaimer. Public patent records should be used to determine the operative expiration date and any adjustment.

The patent issued on May 10, 2011. Issuance does not determine expiration. A patent issued years after filing can retain only the balance of its statutory term, plus qualifying adjustment.

The patent’s exclusivity should be analyzed separately from FDA regulatory exclusivity:

Exclusivity category	Relevance
Patent term	Controls enforceable patent rights
Patent-term adjustment	May extend the base term for USPTO delay
Patent-term extension	May apply only if statutory requirements are met
New drug exclusivity	Depends on the approved NDA and FDA exclusivity record
Orphan exclusivity	Not generally associated with Zipsor
Pediatric exclusivity	Requires an FDA pediatric extension determination
Orange Book listing	Identifies patents submitted for the approved drug

The exact market-entry date for an ANDA applicant depends on the operative patent expiration date, any 30-month stay, litigation outcome, settlement terms and the applicant’s Paragraph IV position.

What is the Orange Book status of the patent?

Zipsor is an FDA-approved prescription drug marketed under an NDA. Patents listed in the FDA Orange Book can impose regulatory consequences for an ANDA applicant that seeks approval of a therapeutically equivalent generic version.

An ANDA applicant generally must make one of four certifications for each listed patent:

Paragraph I: no patent information has been submitted.
Paragraph II: the patent has expired.
Paragraph III: the applicant will wait until patent expiration.
Paragraph IV: the patent is invalid, unenforceable or will not be infringed.

A Paragraph IV notice to the patent owner or NDA holder can trigger patent litigation under the Hatch-Waxman Act. Filing suit within the statutory period can result in a 30-month stay of FDA approval, subject to statutory exceptions and court decisions.[2]

The supplied claim set does not establish the current Orange Book listing status, any delisting, or the existence of a current Paragraph IV challenge. Those issues must be determined from the current FDA Orange Book and federal court docket records rather than from the patent document alone.

Which companies are challenging US 7,939,518?

The claim text alone does not identify an ANDA applicant, Paragraph IV notice, litigation defendant or settlement counterparty. A defensible competitive analysis should distinguish among:

Companies filing a Paragraph IV certification.
Companies filing a Paragraph III certification.
Companies pursuing a non-infringing solid oral formulation.
Companies developing non-diclofenac acute pain products.
Companies marketing products after a settlement or license.

No company should be treated as a confirmed challenger without an FDA notice, complaint, answer, docket entry or settlement filing identifying that company and the patent.

What patent litigation and settlement issues affect market entry?

Potential litigation would focus on five issues.

Infringement

The patent owner would need to prove that the accused product is used under the claimed osteotomy indication, at the claimed dose and interval, in a dispersible liquid formulation. For method claims, induced infringement can be important because the product label or promotional materials may instruct the patented use.

Claim construction

The most contested terms are likely to include:

"Acute post-osteotomy pain."
"Correction of a bone deformity."
"Dispersible liquid formulation."
"About 13 to 30 mg."
"About every 4 hours to about every 8 hours."
"No more than about 100 mg."
"Substantially eliminated."

Validity

A challenger could examine anticipation and obviousness based on earlier diclofenac formulations, postoperative analgesia trials, dosing studies and liquid-filled capsule technology. The combination of a known NSAID, a known surgical pain indication and a rapid-dispersing formulation would likely be central to an obviousness analysis.

Written description and enablement

Claims 9 through 16 include pharmacokinetic and clinical-performance results. A challenger could examine whether the specification adequately supports the full claimed dose range, treatment duration, plasma profile and clinical outcomes.

Settlement

A settlement could permit a generic launch before patent expiration, subject to a date, volume limitation, royalty, license, supply arrangement or other conditions. A settlement cannot be inferred from the patent claims and requires a filed agreement, court order or regulatory record.

How strong is the patent estate for Zipsor?

The estate is strongest against an exact or near-exact copy of the branded product used for the labeled indication. Risk rises when a generic applicant has:

A 25 mg liquid-filled diclofenac potassium capsule.
Labeling that includes acute postoperative pain after bone surgery.
Four-times-daily administration.
A maximum daily dose of 100 mg.
Instructions corresponding to the Zipsor regimen.

Risk is lower for:

Diclofenac potassium tablets.
Diclofenac sodium products.
Doses outside 13 to 30 mg.
Products labeled for unrelated pain indications.
Products with dosing intervals outside approximately 4 to 8 hours.
Products that do not use a dispersible liquid formulation.

The patent is narrower than a formulation patent claiming a complete composition. It is also narrower than a broad method patent covering all acute pain. Its strength comes from alignment with the approved product’s dosage form and labeled regimen.

What generic launch scenarios exist?

Scenario	Likely pathway
Exact 25 mg liquid-filled capsule	High patent scrutiny; likely Paragraph IV or delayed launch
25 mg solid oral tablet	Potential formulation and method-of-use design-around
Different diclofenac salt	May avoid diclofenac potassium limitations
Different dose or interval	May avoid literal infringement, subject to equivalents
Unlabeled postoperative indication	Regulatory and induced-infringement issues become central
Launch after patent expiration	Patent barrier removed, subject to FDA approval
Authorized generic or license	Depends on commercial agreement with patent holder or NDA owner

The principal commercial question is whether a competitor can obtain approval for an alternative formulation while omitting or carving out the patented osteotomy indication. FDA labeling and induced-infringement rules will determine the practical value of that strategy.

How does US 7,939,518 compare with competing diclofenac patent coverage?

Patent category	Typical protection	Relationship to US 7,939,518
Active-ingredient patent	Diclofenac chemical entity	Generally broader, but usually expired
Salt patent	Diclofenac potassium or another salt	May cover composition rather than use
Formulation patent	Liquid-filled capsule, rapid dispersion or excipient system	Could create separate infringement risk
Method-of-use patent	Acute pain or postoperative pain treatment	Overlaps with the patent’s clinical use
Manufacturing patent	Encapsulation, dispersion or filling process	Can block supply even if method claims are avoided
Regulatory exclusivity	NDA-based FDA exclusivity	Separate from patent rights

A freedom-to-operate review must therefore include related formulation, process, method-of-use and Orange Book-listed patents. US 7,939,518 alone does not define the entire Zipsor estate.

What are the key business risks?

The principal risks are:

A generic replicating the 25 mg liquid-filled capsule and labeled dosing regimen.
A Paragraph IV challenge directed to the method claims.
A formulation patent not visible from the supplied claim set.
A court finding that the surgical indication is inherent in the generic label.
A settlement permitting early entry that compresses branded revenue.
Substitution by non-diclofenac acute pain products that avoid the patent estate altogether.

Revenue exposure depends on the product’s remaining branded sales, generic substitution rate, formulary position and the number of viable alternative NSAID products. Patent expiry alone does not determine commercial erosion; FDA approval timing and the scope of any generic label are equally important.

Key Takeaways

US 7,939,518 is a method-of-use patent, not a broad diclofenac composition patent.
Its core coverage is 13 to 30 mg of diclofenac potassium in a dispersible liquid formulation, administered every 4 to 8 hours for at least 24 hours, with a daily maximum of approximately 100 mg.
Bunionectomy is expressly protected by dependent claim 2.
The 25 mg, four-times-daily regimen is the principal commercial embodiment.
Claims 9 through 16 add pharmacokinetic and clinical-performance limitations that may require testing and clinical evidence to enforce.
A conventional diclofenac tablet, a different diclofenac salt or an unrelated indication may avoid literal infringement.
Paragraph IV exposure depends on current Orange Book listings and the facts of any ANDA filing.
The patent’s expiration date must be calculated from the operative filing date, patent-term adjustment and any other statutory term modification.
A complete Zipsor freedom-to-operate analysis must include formulation, manufacturing, method-of-use and regulatory exclusivity records beyond this patent.

FAQs

Does US 7,939,518 cover Zipsor’s 25 mg dose?

Yes. Claim 12 specifically recites approximately 25 mg, and claim 17 covers 25 mg administered four times over approximately 24 hours.

Can a generic avoid the patent by using diclofenac sodium?

Potentially. The claims expressly require diclofenac potassium. Diclofenac sodium would not literally satisfy that limitation, although separate patents, regulatory requirements or equivalence arguments could remain relevant.

Does a six-hour dosing schedule fall within the patent?

Yes. Claim 4 expressly recites administration about every six hours. Claim 3 also covers approximately every 5 to 8 hours.

Is a liquid-filled capsule automatically covered?

No. The capsule must contain diclofenac potassium in the claimed dispersible liquid formulation and be used under the claimed clinical and dosing conditions.

Are biosimilars relevant to this patent?

No. Diclofenac potassium is a small-molecule drug, not a biologic. The relevant competitive products are ANDA generics, authorized generics, alternative NSAID formulations and other acute pain therapies.

References

U.S. Food and Drug Administration. (n.d.). Zipsor (diclofenac potassium) liquid filled capsule prescribing information.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Patent and Trademark Office. (2011). U.S. Patent No. 7,939,518, Methods of treating acute pain.
U.S. Food and Drug Administration. (n.d.). ANDA submissions: Patent certifications and statutory exclusivity provisions.
U.S. Congress. (1984). Drug Price Competition and Patent Term Restoration Act, 21 U.S.C. § 355(j); 35 U.S.C. §§ 154, 156.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Cosette	ZIPSOR	diclofenac potassium	CAPSULE;ORAL	022202-001	Jun 16, 2009	AB	RX	Yes	Yes	7,939,518	⤷ Start Trial				NONSTEROIDAL ANTI-INFLAMMATORY DRUG INDICATED FOR RELIEF OF MILD TO MODERATE ACUTE PAIN	⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Details for Patent: 7,939,518

Which drugs does patent 7,939,518 protect, and when does it expire?

Summary for Patent: 7,939,518