United States Drug Patent 8,765,100: Claim Scope, Fentanyl Buccal Tablet Protection, and Patent Landscape

US Patent No. 8,765,100 protects a specific fentanyl buccal tablet architecture. The independent claim requires four technical features: fentanyl, an effervescent acid-base system, a separate pH-adjusting base in excess of the amount needed for effervescence, and a disintegrant. The patent does not broadly cover every fentanyl buccal dosage form. Its strongest coverage applies to rapidly disintegrating, effervescent tablets that use alkaline excipients to modify the microenvironment at the buccal mucosa.

The narrowest disclosed species in claim 7 uses fentanyl, sodium carbonate as the additional pH-adjusting base, citric acid and sodium bicarbonate as the effervescent pair, and a modified starch as the disintegrant.[1]

What does US Patent 8,765,100 claim?

Claim 1 is an open-ended composition claim. The word "comprising" permits additional ingredients, but the accused tablet must contain every required element.

Required element	Claim requirement	Scope consequence
Active ingredient	Fentanyl and/or a pharmaceutically acceptable salt	Covers fentanyl free base and salts, including fentanyl citrate if the remaining limitations are met
Administration	Amount pharmaceutically effective for buccal mucosal administration in a human	Adds a functional and intended-use limitation
Effervescent couple	About 5% to about 80% by tablet weight	Requires an acid-base effervescent system within the stated range
Effervescent acid	Citric, tartaric, malic, fumaric, adipic, or succinic acid	Closed selection for the claimed acid alternatives
Effervescent base	Sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate, or magnesium carbonate	Closed selection for the claimed base alternatives
Additional pH-adjusting base	Selected carbonate or phosphate bases	Must be present in an amount additional to that required for effervescence
Disintegrant	Up to about 20% by tablet weight	A disintegrant is mandatory
Buccal function	Effective for buccal mucosal administration	Distinguishes the claimed dosage form from conventional swallowed tablets

The claim therefore combines product composition, quantitative limitations, ingredient identity, and intended delivery route. A formulation can contain fentanyl and effervescent excipients yet fall outside claim 1 if it lacks the required additional pH-adjusting base or falls outside the effervescent-couple range.

How broad is the independent claim?

Claim 1 has meaningful breadth at the formulation level but contains several material limitations.

"Comprising" creates an open formulation claim

A tablet can contain binders, lubricants, glidants, flavoring agents, sweeteners, colorants, bioadhesives, or other excipients without escaping claim 1. Claim 4 expressly identifies several of those additional ingredients, but claim 1 already permits them because it uses "comprising."

An accused product does not need to use only the listed excipients. It must, however, include the claimed active, effervescent system, additional pH-adjusting base, and disintegrant.

The effervescent system is limited by both identity and quantity

The effervescent couple must contain at least one acid and at least one base. The acid and base must be selected from the enumerated Markush groups.

The claimed range is about 5% to about 80% by tablet weight. A product with less than approximately 5% or more than approximately 80% may create a noninfringement position, subject to claim construction of "about" and the relevant specification disclosure.

The claim does not require a particular acid-to-base ratio. It also does not require that every listed acid or base be present. One qualifying acid and one qualifying base are sufficient.

The additional-base limitation is central

The pH-adjusting base must be present "in an amount additional to that required for effervescence." This limitation separates the patent from a formulation in which the carbonate or bicarbonate is used only to generate carbon dioxide.

The same base may perform both functions. For example, sodium carbonate can be part of the effervescent couple and also be present in excess as the pH-adjusting base. The claim expressly permits this construction.

This limitation creates a potentially important manufacturing and litigation issue. The relevant question is not simply whether the product contains sodium carbonate or another listed base. The analysis must determine:

The quantity needed for the intended acid-base effervescence.
The total quantity of the base in the tablet.
Whether the difference is an amount additional to the stoichiometric effervescent requirement.
Whether the product's formulation records, batch composition, and process controls support that calculation.

What formulations are protected by claims 2 through 7?

The dependent claims narrow the excipient and ingredient combinations.

Claim 2: disintegrant identity

Claim 2 lists microcrystalline cellulose, croscarmellose sodium, crospovidone, starches, modified starches, sweeteners, clays, alginates, and gums.

The list is technically unusual because some listed materials can perform more than one formulation function. A material categorized commercially as a sweetener or gum may still qualify if it functions as a disintegrant in the tablet.

Claim 3: disintegrant concentration

Claim 3 narrows the disintegrant level to about 2% to about 10% by tablet weight. A product within this range is exposed to both claim 1 and claim 3 if it satisfies the other limitations.

Claim 4: conventional excipients

Claim 4 covers tablets containing one or more glidants, lubricants, binders, sweeteners, flavoring components, or coloring components. This claim adds little exclusionary force against a conventional commercial formulation because most orally disintegrating or buccal tablets use one or more such excipients.

Claim 5: bioadhesive

Claim 5 requires at least one bioadhesive. This claim is commercially relevant because a bioadhesive can prolong contact with the buccal mucosa and influence absorption.

A tablet can infringe claim 1 without containing a bioadhesive. Claim 5 therefore protects a narrower subcategory, not the full claimed platform.

Claim 6: fentanyl citrate

Claim 6 specifically covers fentanyl citrate. It is narrower than claim 1 but commercially significant because fentanyl citrate is a common pharmaceutical form of fentanyl.

A fentanyl citrate tablet that contains the claimed effervescent and pH-adjusting system remains within the scope of claim 6 even if it uses different excipients from the examples.

Claim 7: specific sodium-carbonate formulation

Claim 7 is the most compositionally specific claim. It requires:

fentanyl;
sodium carbonate as the pH-adjusting substance;
citric acid as an effervescent acid;
sodium bicarbonate as an effervescent base; and
at least one modified starch as the disintegrant.

Claim 7 presents a clearer literal-infringement test than claim 1 because the core excipient identities are fixed. It may also be more vulnerable to an invalidity challenge based on a sufficiently close prior-art formulation.

How does claim 7 compare with claim 1?

Issue	Claim 1	Claim 7
Active	Fentanyl or acceptable salt	Fentanyl remains required
Effervescent acid	Six listed acids	Citric acid
Effervescent base	Five listed bases	Sodium bicarbonate
Additional pH base	Seven listed carbonate or phosphate bases	Sodium carbonate
Disintegrant	Any qualifying disintegrant up to about 20%	Modified starch
Commercial breadth	Broadest claim	Narrow species claim
Design-around difficulty	Moderate	Generally easier through excipient substitution
Invalidity exposure	More limitations can support patentability	More specific combination can be easier to match with prior art

What patent landscape surrounds fentanyl buccal tablets?

The relevant landscape has several distinct patent layers. US 8,765,100 is directed to a formulation combination, not to fentanyl as a molecule.

Active-ingredient patents

Fentanyl is an old active pharmaceutical ingredient. Basic composition-of-matter protection for fentanyl is not the principal barrier presented by this patent. Commercial risk instead turns on formulation, delivery system, method-of-use, manufacturing, and regulatory exclusivity rights.

Buccal and transmucosal delivery patents

Earlier fentanyl products include transmucosal lozenges and buccal dosage forms. These products use different delivery mechanisms:

Product type	Delivery route	Formulation distinction
Buccal tablet	Buccal mucosa	Tablet disintegration and mucosal absorption
Oral transmucosal lozenge	Buccal and sublingual exposure	Lozenge or lollipop-style dosage form
Sublingual tablet	Sublingual mucosa	Different placement and absorption profile
Nasal spray	Nasal mucosa	Liquid or spray delivery system
Transdermal system	Skin	Patch-based delivery

A competitor using a nasal spray, transdermal patch, or non-effervescent buccal dosage form would not automatically fall within the claim set. The delivery route and dosage-form limitations matter.

Effervescent and pH-modifying technology

The principal technical concept is an effervescent dosage form that uses an alkaline component beyond the quantity necessary to generate effervescence. The formulation may increase local pH, alter fentanyl dissolution, and support transmucosal uptake.

This creates potential overlap with patent families covering:

effervescent oral dosage forms;
rapidly disintegrating tablets;
pH-modified transmucosal delivery;
bioadhesive dosage forms;
fentanyl buccal absorption;
particle-size and blending controls; and
tablet manufacturing processes.

A freedom-to-operate review should not stop with US 8,765,100. A product may avoid this patent while infringing a separate patent covering the same product's bioadhesive system, manufacturing method, particle engineering, or method of treating breakthrough cancer pain.

What is the Orange Book status of US 8,765,100?

A patent number alone does not establish Orange Book listing status. The FDA Orange Book lists patents submitted by an NDA holder for an approved drug product and accepted under FDA listing rules. A formulation patent may be commercially important without appearing in the Orange Book, particularly if the patent is not submitted for the relevant NDA or does not satisfy the applicable listing criteria.[2]

For an NDA-linked fentanyl buccal product, the Orange Book review should examine:

the active ingredient and dosage form;
patent use codes;
patent expiration dates;
pediatric-exclusivity adjustments;
any delisting or dispute notices; and
whether the listed patent covers the drug, formulation, or method of use.

The Orange Book does not provide a complete patent landscape. It excludes many process, manufacturing, foreign, and non-listed formulation rights.

When does US 8,765,100 lose exclusivity?

The expiration date cannot be calculated from the claim language. US patent term generally runs 20 years from the earliest effective nonprovisional filing date, subject to terminal disclaimers, patent-term adjustment, patent-term extension, and other statutory adjustments.[3]

For this patent, the controlling analysis requires the patent's:

earliest effective priority and nonprovisional filing dates;
patent-term-adjustment calculation;
terminal-disclaimer status;
patent-term-extension status; and
continuity relationship with earlier applications.

The expiration date stated in a commercial database should be reconciled against the USPTO Patent Center record and the patent's front-page term information. A continuation patent can have a different issue date but generally does not receive a new 20-year term measured from the continuation's filing date.

Which companies could challenge the patent?

Potential challengers would include generic manufacturers seeking approval for fentanyl buccal tablets and branded companies developing competing transmucosal products. The likely challenge mechanisms are:

Paragraph IV certification

A generic applicant may certify that the patent is invalid, unenforceable, or will not be infringed. A Paragraph IV notice can trigger Hatch-Waxman litigation and, for an applicable listed patent, a statutory stay of FDA approval for up to 30 months under the conditions in 21 U.S.C. § 355(j).[4]

A challenge to claim 1 would likely focus on:

anticipation by an earlier fentanyl buccal formulation;
obviousness based on combining known effervescent and pH-adjusting excipients;
lack of written description for the full Markush combinations;
lack of enablement across the full 5% to 80% effervescent range; and
indefiniteness of "about" or "amount required for effervescence."

Inter partes review

An accused company or other eligible petitioner may consider inter partes review for patentability challenges based on patents and printed publications. IPR cannot resolve every infringement or enforceability issue, and it does not replace district-court litigation.[5]

Design-around

A generic company may avoid the most important limitations by using:

a non-effervescent tablet;
an effervescent system outside the claimed acid and base lists;
no pH-adjusting base beyond the effervescent requirement;
a delivery route other than buccal mucosal administration;
a different dosage form;
a disintegrant strategy outside the claimed limitations; or
a formulation that uses an alternative pH modifier not listed in the claim.

Each design-around must be tested against the doctrine of equivalents and other patents in the surrounding delivery platform.

How strong is the patent estate?

US 8,765,100 has moderate formulation-claim strength if the commercial product uses the listed excipient architecture. Its practical value is strongest where analytical testing can demonstrate:

The effervescent couple falls within the claimed percentage range.
The acid and base identities match the claim.
A listed pH-adjusting base is present in excess of the effervescent requirement.
The product is intended and suitable for human buccal administration.
A qualifying disintegrant is present.

The claim is weaker against products that use a different delivery mechanism or avoid the additional-base limitation. Its validity risk increases if prior art discloses fentanyl buccal tablets containing the same acid-base system, elevated pH environment, and rapid disintegration characteristics.

The patent should therefore be treated as one formulation asset within a larger patent thicket, rather than as a standalone barrier to all fentanyl generic entry.

What litigation and settlement issues matter?

A patent litigation review should separate three issues:

whether the patent was asserted;
whether the asserted claims survived claim construction, summary judgment, or trial; and
whether any settlement authorized an earlier generic launch.

A settlement may include a licensed entry date, supply arrangement, authorized-generic provision, or restrictions unrelated to the patent's ultimate validity. The absence of a reported case does not establish absence of enforcement, because disputes may resolve through confidential agreements or administrative proceedings.

For transaction diligence, the relevant records include USPTO Patent Center, district-court dockets, Federal Circuit opinions, FDA Orange Book listings, ANDA litigation notices, and any public settlement filings.

Key Takeaways

US 8,765,100 is a formulation patent for a fentanyl buccal tablet with an effervescent couple, an additional pH-adjusting base, and a disintegrant.
Claim 1 is broad within that architecture but does not cover every fentanyl buccal, sublingual, nasal, transdermal, or oral product.
The phrase requiring the pH-adjusting base to be present in an amount additional to that required for effervescence is a central claim limitation.
Claim 7 is a narrower species claim centered on citric acid, sodium bicarbonate, sodium carbonate, and modified starch.
A generic challenger could focus on anticipation, obviousness, claim construction, written description, enablement, or a noninfringing formulation design.
Orange Book listing cannot be inferred from the patent number alone, and Orange Book data would not capture the full formulation and manufacturing patent landscape.
Patent expiration must be verified from the patent's continuity, term-adjustment, terminal-disclaimer, and extension records.
Commercial entry risk depends on the complete patent family and the approved product's actual formulation, not US 8,765,100 in isolation.

FAQs About US Patent 8,765,100 and Fentanyl Buccal Tablets

Does a fentanyl citrate tablet automatically infringe US 8,765,100?

No. Fentanyl citrate satisfies the active-ingredient limitation in claim 6, but infringement also requires the claimed effervescent system, additional pH-adjusting base, buccal administration characteristics, and disintegrant.

Can a formulation avoid the patent by replacing sodium bicarbonate?

Potentially. Replacing sodium bicarbonate may avoid claim 7, but claim 1 covers several alternative effervescent bases. The replacement must be assessed against the entire claim set and the doctrine of equivalents.

Does a pH-adjusting phosphate create infringement risk?

Yes, if the product otherwise satisfies claim 1. Claim 1 expressly lists disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate as possible pH-adjusting bases.

Does the patent cover fentanyl nasal spray?

The supplied claims are directed to a tablet for buccal mucosal administration. A fentanyl nasal spray would not ordinarily satisfy the tablet and buccal-administration limitations, although separate patents could apply.

Is claim 7 required for a patent-infringement case?

No. An infringement case could assert claim 1 or another claim without proving the narrower combination in claim 7. Claim 7 provides an additional, more specific claim position.

References

United States Patent No. 8,765,100, claims 1-7 (U.S. Patent and Trademark Office).
U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations (Orange Book).
35 U.S.C. §§ 154, 156 (2024).
21 U.S.C. § 355(j) (2024).
35 U.S.C. §§ 311-319 (2024).

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	350017	⤷ Start Trial
Austria	433745	⤷ Start Trial
Austria	434432	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,765,100

Summary for Patent: 8,765,100