# United States Patent 8,449,910: Claim Scope, Duexis Patent Protection, Orange Book Status, and Generic Entry Risk

US Patent No. 8,449,910 protects immediate-release, single-tablet ibuprofen/famotidine combinations that use physically contacting drug regions, limit ibuprofen-famotidine contact, and satisfy specified stability or degradation criteria. The patent is directed to the Duexis formulation, containing 800 mg ibuprofen and 26.6 mg famotidine. Its principal commercial value is formulation protection rather than protection for either active ingredient alone.

The claims require a narrow combination of:

Ibuprofen and famotidine in specified dose ranges.
A single tablet unit dosage form.
Separate layers, regions, or compartments for the two active ingredients.
Direct contact between the ibuprofen and famotidine regions.
Immediate and approximately simultaneous release.
No enteric, sustained-release, delayed-release, or barrier-layer structure in the principal claim categories.
Direct drug contact of no more than 130 mm².
Stability against sulfamide formation or loss of active ingredient under accelerated storage conditions.
Exclusion of certain tablet-in-tablet configurations.

What does US Patent 8,449,910 protect?

The patent protects a pharmaceutical composition combining high-dose ibuprofen with low-dose famotidine in a physically integrated immediate-release tablet. The broadest independent claims are claims 1, 16, 22, and 24.

Claim	Principal formulation format	Key narrowing limitations
1	Bilayer tablet	750-850 mg ibuprofen; 24-28 mg famotidine; direct-contact layers; immediate release; no barrier layer stated only through dependent claim 27; contact area no greater than 130 mm²
16	Single tablet with first and second physical regions	No barrier layer; rapid, approximately simultaneous release; direct contact; tablet-in-tablet exception differs from claim 1
22	Specific composition	800 mg ibuprofen; 26.6 mg famotidine; carboxymethylcellulose salt, colloidal silicon dioxide, and microcrystalline cellulose in the ibuprofen layer; colloidal silicon dioxide and microcrystalline cellulose in the famotidine layer
24	Single tablet with distinct compartments	Directly contacting compartments; immediate release; stability or active-retention alternative; no tablet-in-tablet formulation with famotidine shell surrounding ibuprofen core

The patent does not broadly claim all ibuprofen/famotidine combinations. A competing product must satisfy every limitation of at least one asserted claim, either literally or under an applicable doctrine of equivalents.

What are the active-ingredient and dosage limitations?

Claims 1, 16, and 24 require:

Ibuprofen: 750 mg to 850 mg.
Famotidine: 24 mg to 28 mg.

Claim 22 is narrower and requires:

800 mg ibuprofen.
26.6 mg famotidine.

The ranges are composition limitations, not merely target label strengths. A formulation containing 700 mg ibuprofen or 40 mg famotidine would fall outside these express dose limitations, although other claims, patents, or infringement theories could remain relevant.

The claim language covers ibuprofen and famotidine as active pharmaceutical ingredients. It does not require a particular ibuprofen salt, particle-size distribution, polymorph, or famotidine solid form in the quoted claims.

How does the bilayer-tablet limitation affect infringement?

Claim 1 is directed to a bilayer tablet in which:

Ibuprofen is in a first layer.
Famotidine is in a second layer.
The second layer directly contacts the first layer.
At least one binder is present in one or both layers.
Both active ingredients are formulated for immediate release.

A conventional bilayer tablet with ibuprofen in one layer and famotidine in the adjacent layer is the clearest literal risk profile. A barrier film or separating layer may avoid claim 1 if the barrier prevents the required direct contact, but claim construction would determine whether a particular coating, interface treatment, or excipient-rich zone constitutes a separate barrier layer.

Claim 27 narrows claim 1 by expressly requiring no barrier layer between the two layers. Claims 16, 22, and 24 contain similar direct-contact concepts in their independent claim language.

What is the significance of the 130 mm² direct-contact limitation?

The 130 mm² limitation is a central design-around feature. The claims require direct contact between ibuprofen and famotidine, but cap the contact area at no more than approximately 130 mm².

This creates two competing infringement questions:

A product with no direct contact may avoid the claim.
A product with direct contact exceeding 130 mm² may also avoid the claim.
A product with a direct interface at or below 130 mm² remains within the literal scope if all other limitations are met.

The patent therefore does not protect every adjacent-layer configuration. It targets controlled physical contact intended to reduce interaction between ibuprofen and famotidine while preserving rapid, simultaneous release.

The contact-area limitation may generate factual disputes over:

Whether the relevant area is the tablet-face area or the actual drug-to-drug contact area.
Whether excipients at the interface interrupt direct active-ingredient contact.
Whether compression causes interpenetration between layers.
Whether the measured area changes after storage.
Whether “about 130 mm²” allows a tolerance beyond 130 mm².

These issues are likely to require formulation records, cross-sectional microscopy, tablet tooling data, and manufacturing-process evidence.

What stability and sulfamide limitations are claimed?

The claims use alternative stability requirements. Depending on the claim, the formulation must satisfy either:

No more than approximately 1% sulfamide after storage at 40°C and 75% relative humidity for a specified period; or
At least 90% of the initial ibuprofen and famotidine remaining after the same storage condition.

Claims 2 through 6 and 17 through 21 add sulfamide limits at one, three, or six months. Claims 25 and 26 require at least 95% retention of ibuprofen or famotidine after one month.

Claim group	Stability requirement
Claims 1, 16, 22, 24	Approximately 1% or less sulfamide after one month, or at least 90% retention of both actives after one month
Claims 2, 6, 17, 18	Approximately 1% or less sulfamide after three or six months
Claims 3, 4, 5, 19, 20, 21	Approximately 0.6% or less sulfamide after one, three, or six months
Claims 25-26	At least 95% retention of ibuprofen or famotidine after one month

The claims do not merely require an initially stable tablet. They impose performance criteria under an accelerated condition. A generic developer would need stability data using the claimed dosage, packaging, analytical method, and storage protocol.

The meaning of “sulfamide” may also affect enforcement. The relevant degradation product must be identified through the patent specification, validated analytical method, and regulatory product specifications. A formulation that produces a different degradation profile could avoid the sulfamide limitation while still raising issues under other patent claims.

What excipients and formulation technologies are covered?

Dependent claims cover common immediate-release excipients rather than an exclusive proprietary excipient system.

Ibuprofen-layer excipients

Claim 7 covers disintegrants selected from:

Starch derivatives.
Carboxymethylcellulose salts.
Crospovidone.

Claim 8 covers glidants selected from:

Colloidal silicon dioxide.
Talc.
Corn starch.

Claims 9 and 10 cover cellulose-derived binders, including:

Powdered cellulose.
Microcrystalline cellulose.
Silicified microcrystalline cellulose.
Hydroxypropylcellulose.
Low-substituted hydroxypropylcellulose.
Hydroxypropylmethylcellulose.

Claim 14 specifically requires a first layer containing:

A carboxymethylcellulose salt.
Colloidal silicon dioxide.
Microcrystalline cellulose.

Famotidine-layer excipients

Claim 11 covers the same principal glidant group for the second layer. Claims 12 and 13 cover cellulose-derived binders in the famotidine layer.

Claim 15 specifically requires:

Colloidal silicon dioxide.
Microcrystalline cellulose.

Claim 22 combines these specific excipient limitations with 800 mg ibuprofen and 26.6 mg famotidine. It is narrower than claims 1, 16, and 24 but may be commercially important because it tracks the Duexis-type formulation more closely.

How do the independent claims differ?

The independent claims overlap but are not identical.

Claim 1

Claim 1 is the main bilayer claim. It requires the ibuprofen and famotidine APIs to be in separate layers that directly contact each other. It excludes a tablet-in-tablet structure in which a famotidine shell completely surrounds an ibuprofen core.

Claim 16

Claim 16 uses “first physical region” and “second physical region” rather than expressly requiring layers. It requires no barrier layer between the regions. Its tablet-in-tablet proviso permits a configuration in which the famotidine region is completely surrounded by the ibuprofen region, subject to the other limitations.

This difference may matter for three-dimensional tablets, compartmentalized tablets, and tablets made by sequential compression rather than conventional two-layer compression.

Claim 22

Claim 22 is a formulation-specific claim. It is directed to the 800 mg/26.6 mg strength and named excipient combination. It also expressly permits the bilayer format through dependent claim 23.

Claim 24

Claim 24 covers distinct compartments in direct contact. It is structurally broader than a conventional bilayer claim in terminology, but still requires immediate release, rapid approximately simultaneous release, direct contact, and the 130 mm² contact-area limit.

When does US Patent 8,449,910 lose exclusivity?

US Patent 8,449,910 was issued on May 28, 2013. Public patent records identify a September 14, 2007 priority date for the relevant family. The ordinary patent-term framework points to expiration in September 2028, subject to any patent-term adjustment, terminal disclaimer, patent-term extension, or other USPTO term calculation shown in the official patent record. The FDA Orange Book controls the regulatory listing and expiration information used for ANDA certification purposes, while the USPTO controls patent-term determination.[1][2]

The patent does not provide a new chemical entity exclusivity period for ibuprofen or famotidine. Both active ingredients are longstanding drugs. Its commercial exclusivity depends on formulation patents, FDA listing, regulatory exclusivity, enforcement activity, and the ability of an ANDA applicant to establish noninfringement or invalidity.

What is the FDA regulatory and Orange Book status?

Duexis is an FDA-approved prescription product containing 800 mg ibuprofen and 26.6 mg famotidine in a single immediate-release tablet. The product was approved under NDA 022519 on April 23, 2011, according to FDA product records.[3]

The regulatory product is distinct from over-the-counter ibuprofen and famotidine products because it combines prescription-strength ibuprofen with famotidine in one unit dosage form. FDA approval does not itself establish patent validity, but Orange Book listing gives the patent procedural significance for ANDA applicants.

Relevant regulatory issues include:

A generic applicant must address each listed patent through a Paragraph I, II, III, or IV certification.
A Paragraph IV certification alleges that the listed patent is invalid, unenforceable, or not infringed.
Timely patent litigation after a Paragraph IV notice can trigger a 30-month stay of ANDA approval under the Hatch-Waxman Act.
The FDA generally cannot approve the ANDA during the applicable stay unless the litigation is resolved earlier or the stay expires.

The Orange Book listing should be reviewed by NDA, patent number, and expiration date because listed patents can change through corrections, delistings, patent-term adjustments, or product-specific updates.[1]

Which companies are challenging Duexis patent protection?

Generic competition has involved ANDA applicants seeking to market ibuprofen/famotidine combination products. Publicly reported Hatch-Waxman disputes have included litigation involving Horizon Pharma and generic applicants such as Dr. Reddy’s Laboratories and other manufacturers. The relevant disputes have focused on Duexis-related formulation patents, including US 8,449,910 and related continuation patents.

A complete litigation determination requires reviewing:

The ANDA applicant’s Paragraph IV notice.
The asserted claims.
The district-court docket.
Any Federal Circuit appeal.
Claim-construction rulings.
Settlement terms.
FDA approval status.

The patent landscape should not be assessed from the existence of a lawsuit alone. A generic defendant may challenge one patent while leaving other listed patents in force. Conversely, a settlement can establish an agreed launch date without producing a judicial ruling on validity or infringement.

What related patents may affect generic entry?

US 8,449,910 is part of a broader family and should be analyzed with related continuation and formulation patents. Public patent databases identify later Duexis-related patents, including US 8,673,958, as part of the same general ibuprofen/famotidine formulation landscape.[4]

The relevant portfolio can include:

Patent category	Commercial purpose
Bilayer and direct-contact composition claims	Protect the physical arrangement of ibuprofen and famotidine
Stability claims	Protect reduced sulfamide formation and active retention
Excipient-specific claims	Cover selected binders, disintegrants, glidants, and cellulose systems
Dosage-specific claims	Track 800 mg ibuprofen and 26.6 mg famotidine
Continuation claims	Preserve overlapping but differently worded claim sets
Method-of-use claims	Potentially cover prevention or reduction of NSAID-associated gastric injury

The supplied claims are composition claims. They do not claim a treatment method, manufacturing process, tablet press, packaging system, or method of reducing gastric ulcer risk. Separate patents may cover those subjects.

What manufacturing and intellectual-property barriers exist?

A generic manufacturer faces both legal and technical barriers.

Technical barriers

The product must be manufactured with:

Consistent layer weight.
Uniform API distribution.
Controlled interfacial contact.
Rapid release of both actives.
Adequate mechanical strength.
Low cross-layer migration.
Stability under high humidity.
Controlled sulfamide formation.
Reproducible tablet dimensions and contact geometry.

A formulation that uses a separating layer may improve stability but risk falling outside the claimed direct-contact architecture. A formulation that maximizes direct contact may increase degradation or create dissolution variability.

Intellectual-property barriers

The principal legal risks include:

Literal infringement of a listed composition claim.
Infringement of a continuation patent with different structural language.
Failure to prove that the product lacks the 130 mm² contact limitation.
Failure to meet a Paragraph IV noninfringement position after claim construction.
Exposure to a method-of-use patent even if the composition patent is avoided.
Manufacturing disclosures in the ANDA that reveal direct-contact geometry and excipient composition.

How strong is the patent estate for Duexis?

The estate is strongest against a close copy of the marketed product: an 800 mg/26.6 mg immediate-release bilayer tablet with direct-contact regions, limited interface area, cellulose-based excipients, and documented stability performance.

Its strength is lower against products that materially change one of the required architectural elements, such as:

A multilayer design with a true barrier layer.
Separate capsules or separate tablets.
A tablet with no direct API-to-API contact.
A contact area above 130 mm².
A dose outside the specified ranges.
A delayed-release or enteric formulation.
A product using a different physical compartment arrangement.
A formulation that fails the claimed stability criteria.

The estate’s durability depends on the validity of the direct-contact and stability limitations, the written-description support for the claim breadth, and the scope of any related continuation patents. The common excipient classes in claims 7-15 are less commercially distinctive than the combination of dose, geometry, release profile, and accelerated-stability performance.

What generic launch scenarios exist?

Launch scenario	Practical outcome
Paragraph III certification	Launch delayed until the relevant patent expiration
Paragraph IV certification with prompt litigation	Potential 30-month FDA approval stay
Successful noninfringement position	Launch possible after regulatory requirements and applicable stay
Successful invalidity challenge	Listed patent no longer blocks approval
Settlement with licensed entry	Launch on the agreed settlement date
Design-around product	Entry depends on avoiding all asserted composition and method claims
Separate ibuprofen and famotidine products	Avoids the single-tablet composition claims but does not replicate Duexis

A formulation design-around must be evaluated against the complete Orange Book portfolio, not US 8,449,910 in isolation.

Does US 8,449,910 create biosimilar risk?

No. Biosimilar risk is not relevant to this patent because ibuprofen and famotidine are chemically synthesized small-molecule active ingredients, not biological products regulated through the biosimilar pathway under the Public Health Service Act. The relevant competitive pathway is an ANDA for a generic drug, not a 351(k) biosimilar application.

What is the commercial exposure from this patent?

The patent protects a branded prescription combination with two differentiated commercial attributes:

Prescription-strength ibuprofen at 800 mg.
Famotidine coadministration in the same immediate-release tablet.

Revenue exposure depends on the extent to which Duexis sales rely on the single-tablet convenience and whether generic manufacturers can reproduce the formulation without infringing listed patents. A successful generic launch would likely pressure price, payer coverage, and market share even if branded patients continue using the product for convenience.

The patent alone does not establish the value of the product. Commercial exposure must be assessed against the entire Orange Book listing, settlement dates, generic approvals, formulary substitution, and the availability of lower-cost separate ibuprofen and famotidine products.

Key Takeaways

US 8,449,910 is a formulation patent for an immediate-release ibuprofen/famotidine single-tablet product.
Its commercial center is the 800 mg ibuprofen/26.6 mg famotidine Duexis configuration.
The principal structural limitations are separate drug regions, direct contact, no more than approximately 130 mm² contact area, and rapid approximately simultaneous release.
Stability limitations target sulfamide formation and retention of the active ingredients under 40°C/75% relative humidity conditions.
Claims 1, 16, 22, and 24 overlap but use different layer, region, compartment, and tablet-in-tablet language.
Claims 7-15 and 22 add excipient-specific limitations, including cellulose derivatives, carboxymethylcellulose salts, colloidal silicon dioxide, and microcrystalline cellulose.
The patent is not a biosimilar barrier. Generic ANDA litigation is the relevant competitive framework.
A product that uses a barrier layer, eliminates direct contact, changes the contact area, or moves outside the claimed dose range may have a stronger design-around position.
The patent should be analyzed together with related continuation patents, Orange Book listings, Paragraph IV notices, and any settlement agreements.
Based on the identified priority framework, the expected ordinary term reaches into September 2028, subject to the official USPTO and Orange Book term records.

FAQs About US Patent 8,449,910 and Duexis

Does US 8,449,910 cover standalone ibuprofen?

No. The claims require a composition containing both ibuprofen and famotidine in the claimed dosage and structural arrangement.

Does the patent cover separate ibuprofen and famotidine tablets?

No. The asserted claims require a single tablet unit dosage form or a bilayer, region-based, or compartment-based tablet structure.

Can a generic use a barrier layer to avoid the patent?

A true barrier layer may avoid claims requiring direct contact or no barrier layer. The complete claim set and related patents must be reviewed because a different continuation patent may use broader structural language.

Does the 130 mm² limitation apply to the whole tablet?

The claim language refers to direct contact between the ibuprofen and famotidine APIs. The relevant measurement is the qualifying API-to-API contact area, not necessarily the tablet’s total surface area.

Is famotidine itself patent-protected by US 8,449,910?

No. The patent does not claim famotidine as a standalone active ingredient. It claims famotidine in combination with ibuprofen within the specified tablet architecture and stability framework.

References

U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
United States Patent and Trademark Office. (2013). U.S. Patent No. 8,449,910, pharmaceutical compositions comprising ibuprofen and famotidine. U.S. Department of Commerce. https://patents.google.com/patent/US8449910B2/en
U.S. Food and Drug Administration. (2011). Drugs@FDA: Duexis, NDA 022519. https://www.accessdata.fda.gov/scripts/cder/daf/
United States Patent and Trademark Office. (2014). U.S. Patent No. 8,673,958, pharmaceutical compositions comprising ibuprofen and famotidine. U.S. Department of Commerce. https://patents.google.com/patent/US8673958B2/en

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Horizon	DUEXIS	famotidine; ibuprofen	TABLET;ORAL	022519-001	Apr 23, 2011		DISCN	Yes	No	8,449,910	⤷ Start Trial	Y				⤷ 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

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	E539747	⤷ Start Trial
Australia	2006269894	⤷ Start Trial
Australia	2007275360	⤷ Start Trial
Brazil	PI0714937	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,449,910

Which drugs does patent 8,449,910 protect, and when does it expire?

Summary for Patent: 8,449,910