United States Patent 6,200,604: Claim Scope, Expiration, and Oral Transmucosal Drug-Delivery Landscape

United States Patent 6,200,604 covers a method for administering a systemic drug through the oral mucosa using a saliva-activated effervescent solid dosage form. Its core requirement is not merely an effervescent tablet. The method requires the patient to hold the dosage form in the mouth while the effervescent reaction promotes buccal, sublingual, or gingival absorption.

The patent’s operative term has expired. The patent therefore does not create a current exclusionary right against generic or branded products. Its technical concepts remain relevant to later formulation and delivery patents, particularly those directed to fast-dissolving, bioadhesive, pH-modified, or transmucosal dosage forms.

What does United States Patent 6,200,604 protect?

The independent claim protects a patient-use method with six central elements:

A solid oral dosage form.
A pharmaceutically effective amount of an orally administerable medicament.
At least one effervescent agent.
The effervescent agent is present in an amount sufficient to increase absorption across the oral mucosa.
The medicament is not substantially enclosed in or dispersed through a material that prevents oral-mucosal absorption.
The patient holds the dosage form and its dissolving contents in the mouth while saliva activates the effervescent agent.

The claim is directed to use, not to an unrestricted composition. A product would not infringe claim 1 merely because it contains a drug and an effervescent system. The claimed administration steps also must occur.

Patent identification

Field	Information
Patent	U.S. Patent No. 6,200,604
Title	Effervescent oral dosage forms
Patent type	Utility patent
Technology	Oral transmucosal delivery using effervescence
Filing date	October 16, 1998
Earliest priority	October 17, 1997
Issue date	March 13, 2001
Recorded assignee	Fuisz Technologies, Ltd.
Claim category	Method of administering a systemic pharmaceutical agent
Operative expiration	October 16, 2018
Current enforceability	Expired

The patent term is governed by the 20-year term applicable to applications filed after June 8, 1995, subject to any applicable patent-term adjustment or terminal disclaimer. The public patent record identifies the patent as expired. See 35 U.S.C. § 154; U.S. Patent and Trademark Office, Patent Center.

How broad is claim 1 of U.S. Patent 6,200,604?

Claim 1 is technically broad but legally constrained by its functional and procedural limitations.

Broad elements

The claim does not restrict the medicament to a named active ingredient. It covers a systemically distributable pharmaceutical agent that can be administered orally. The claim also does not require a specific effervescent pair, such as an acid and bicarbonate, or a particular tablet manufacturing process.

The claim does not require:

A particular tablet weight.
A specific drug concentration.
A specified dissolution time.
A named bioadhesive.
A particular pH.
A specific oral-mucosal site.
A particular gas-generating chemistry.
A particular commercial dosage form brand.

This creates a broad genus covering many potential active ingredients and excipient combinations.

Limiting elements

The following limitations materially narrow claim 1:

The dosage form must be solid.
Saliva must activate the effervescent agent.
The dosage form must be held in the mouth.
Absorption must occur across the oral mucosa.
The effervescent system must promote or increase absorption.
The medicament cannot be substantially protected from oral-mucosal absorption by an enclosing or dispersing material.

A conventional effervescent tablet that is swallowed immediately would generally fall outside the claimed method because the claim requires oral-mucosal contact and retention. A sublingual product that dissolves without effervescence may also fall outside claim 1 unless the claimed absorption-promoting effervescent limitation is satisfied.

What are the dependent claim limitations?

The dependent claims divide the platform into formulation, administration-site, ingredient-class, and effervescent-quantity limitations.

Claim	Added limitation	Practical scope
2	pH-adjusting substance	Covers pH modification as part of the dosage form
3	Buccal placement	Requires holding the dosage form adjacent to the cheek
4	Sublingual placement	Requires holding the dosage form beneath the tongue
5	Gingival placement	Requires holding it between the upper lip and gum
6	Bioadhesive	Requires increased contact time with oral mucosa
7	Conventional excipients	Covers glidants, lubricants, binders, sweeteners, flavors, and colors
8	Broad small-molecule drug classes	Includes analgesics, antibiotics, antihistamines, antihypertensives, beta blockers, and other listed classes
9	Peptides, proteins, and oligonucleotides	Extends the genus to macromolecular therapeutics
10	Effervescent agent at 5% to 95% by weight	Broad quantitative range
11	Effervescent agent at 30% to 80% by weight	Narrower quantitative range
12	Gas evolution of approximately 5 to 30 cm as stated	Quantitative gas-generation limitation

The supplied claim text contains apparent transcription errors, including "at leant," "it the mouth," "claim or 1 or 2," "stop c)," and "anti-emtics." The issued patent text, rather than an OCR or manually transcribed version, controls claim interpretation. Claim 12 should also be checked against the issued document because a gas-volume limitation would ordinarily be expressed in cubic centimeters or another defined unit.

What formulations are protected by U.S. Patent 6,200,604?

The patent reaches several formulation architectures when used with the required administration steps.

Effervescent oral transmucosal tablets

The principal formulation is a solid dosage form that generates gas after contact with saliva. The effervescent reaction may improve wetting, dissolution, local mixing, mucosal contact, or transport across the oral mucosa.

The claim does not require that the gas itself cross the mucosa. The relevant legal question is whether the effervescent system promotes absorption of the medicament across the oral mucosa.

pH-adjusted formulations

Claim 2 covers formulations containing a pH-adjusting substance. A pH modifier could affect:

Drug ionization.
Solubility.
Chemical stability.
Mucosal permeability.
Effervescent reaction rate.
Local irritation or tolerability.

A pH-adjusted tablet is not independently infringing. It must still satisfy the method limitations of an underlying claim.

Bioadhesive formulations

Claim 6 covers a bioadhesive that increases contact time between the dosage form and the oral mucosa. This limitation is relevant to mucoadhesive polymers and other retention systems used for buccal, sublingual, or gingival delivery.

The claim does not define a specific bioadhesive material or minimum residence time. That breadth creates potential written-description and enablement questions for particular formulations, but it also makes the claim difficult to avoid where a product intentionally uses adhesive retention and the other claim elements are present.

Unprotected or readily available drug

The exclusion concerning a medicament not being "substantially encompassed by or dispersed in a material that prevents absorption" is important. It distinguishes the claimed system from dosage forms in which the drug is encapsulated, coated, embedded, or otherwise shielded from the oral mucosa.

The limitation should not be read as requiring the drug to be entirely unformulated. Excipients, binders, flavors, lubricants, and bioadhesives can remain present. The issue is whether the surrounding material prevents the drug from being available for transmucosal absorption.

How do the claims apply to buccal, sublingual, and gingival delivery?

Claims 3 through 5 create separate administration-site embodiments.

Buccal delivery

Claim 3 covers holding the dosage form adjacent to the cheek. A product designed to dissolve against the buccal mucosa would be the closest commercial analogue to this claim.

Sublingual delivery

Claim 4 covers placement beneath the tongue. The claim does not require rapid dissolution, a particular sublingual blood concentration, or a named sublingual active ingredient.

Gingival delivery

Claim 5 covers placement between the upper lip and gum. This limitation is narrower than the general oral-mucosal language in claim 1 and may have reduced practical relevance for products designed solely for buccal or sublingual placement.

The three claims are use-position claims. A product’s labeling, instructions, patient training, and actual administration practice would be relevant to infringement analysis.

What drug classes and products could fall within the patent?

Claim 8 lists a broad group of small-molecule therapeutic categories. Claim 9 separately includes peptides, proteins, and oligonucleotides.

Potentially relevant categories include:

Analgesics and antipyretics.
Anti-inflammatory drugs.
Antibiotics and antimicrobials.
Antihistamines and decongestants.
Antiasthmatic agents.
Antimigraine agents.
Antispasmodics and sedatives.
Antihypertensive agents.
Beta blockers.
Peptides and proteins.
Oligonucleotides.

The listed classes do not automatically establish infringement for every drug in the category. The active ingredient must be administered through a qualifying solid effervescent dosage form, and the administration must satisfy the oral-mucosal limitations.

The inclusion of peptides, proteins, and oligonucleotides is commercially significant because oral mucosal delivery can address gastrointestinal degradation and hepatic first-pass exposure. It also creates a potential validity issue because a genus extending across diverse macromolecules may face written-description or enablement scrutiny depending on the specification and evidence available during prosecution or litigation.

How strong is the patent estate for U.S. Patent 6,200,604?

The patent’s historical strength was mixed. Its independent claim was broad in active ingredient and excipient selection, but it depended on a specific mechanism and patient-use sequence.

Strengths

Broad active-ingredient coverage.
No requirement for a named drug.
No requirement for a particular effervescent chemistry.
Coverage of buccal, sublingual, and gingival administration.
Express coverage of bioadhesive and pH-adjusted embodiments.
Inclusion of peptides, proteins, and oligonucleotides.

Weaknesses

The claims are method claims rather than composition claims.
The effervescent agent must promote increased mucosal absorption.
The patient must retain the dosage form in the mouth.
The claim contains functional language that could require pharmacokinetic or mechanistic proof.
Oral dosage forms, effervescent systems, buccal delivery, sublingual delivery, and bioadhesive tablets were established technical fields before the filing date.
The breadth of the drug and biologic genus could raise Section 112 issues.
The patent is expired, eliminating prospective injunctive and infringement leverage.

The most important practical distinction is between technical breadth and current legal value. The claims remain technically broad as a description of a delivery concept, but they no longer provide enforceable exclusivity.

When did U.S. Patent 6,200,604 lose exclusivity?

The patent lost exclusivity when its statutory term ended on October 16, 2018. The expiration date is more important than the 2001 issue date because the patent term is generally measured from the relevant filing date, not from grant.

Event	Date
Earliest priority	October 17, 1997
Nonprovisional filing	October 16, 1998
Patent issued	March 13, 2001
Statutory term endpoint	October 16, 2018
Current status	Expired

An expired patent cannot support a new Paragraph IV litigation strategy seeking to block an ANDA launch. It also cannot independently justify a royalty on post-expiration sales unless a separate contract contains enforceable post-expiration obligations.

What is the Orange Book status of U.S. Patent 6,200,604?

Patent 6,200,604 is not an Orange Book right merely because it is a U.S. drug patent. Orange Book listing depends on submission by an approved NDA holder and association with a specific approved drug product.

The patent claims a platform method covering unspecified medicaments. They do not identify a particular approved active ingredient, dosage strength, or NDA product. On that basis, the patent has no product-specific Orange Book significance independent of an approved product submission. FDA Orange Book patent listings are tied to approved drug applications and listed patent information, not to all patents that mention pharmaceutical delivery technologies (FDA, 2024a).

Are Paragraph IV challenges relevant to this patent?

A Paragraph IV certification is relevant when an ANDA applicant challenges a patent listed for the reference listed drug. Patent 6,200,604 does not create a current Paragraph IV barrier because its term has expired.

Historically, an ANDA applicant could have faced a patent issue if the patent had been properly listed against a reference product and remained unexpired. The relevant exposure would have depended on:

Whether the patent was listed for the reference product.
Whether the ANDA product used the claimed dosage form.
Whether the ANDA labeling instructed buccal, sublingual, or gingival administration.
Whether the effervescent system increased oral-mucosal absorption.
Whether the applicant could certify noninfringement or invalidity.

A generic product using an ordinary swallowed effervescent tablet would present a weaker read on the claims than a product expressly labeled for buccal or sublingual retention.

Does the patent create biosimilar risk?

The patent does not create current biosimilar risk because it has expired. Its inclusion of peptides and proteins does not convert it into a biologic patent in the modern regulatory sense.

A biosimilar applicant would generally proceed under the Public Health Service Act section 351(k), not through an ANDA Paragraph IV certification against an Orange Book-listed patent. Patent disputes would instead involve biologic patent disclosures, the section 351(l) information-exchange process, and conventional patent litigation. The expired status of U.S. 6,200,604 removes this patent from that dispute set (FDA, 2024b).

Which companies are challenging or licensing this patent?

The claim text does not establish a licensing agreement, assignment history, litigation record, or challenge by a particular company. Patent ownership and licensing must be distinguished:

The recorded assignee identifies title in the patent register.
A license may be private and may not appear in the patent document.
A patent assignment does not disclose all royalty or commercialization terms.
A historical litigation record would require a case-specific court-docket review.
Expiration eliminates ongoing patent-enforcement value even if historical licenses existed.

No current generic launch restriction, Paragraph IV settlement, or royalty obligation follows from the expired patent alone.

What patent landscape surrounds oral effervescent transmucosal delivery?

The relevant landscape has four layers.

Platform delivery patents

These patents claim the general use of effervescence, rapid dissolution, mucosal contact, or gas generation to improve systemic delivery. U.S. 6,200,604 belongs to this layer.

Formulation patents

Later patents may claim:

Specific acid-base effervescent pairs.
Polymer and bioadhesive systems.
Taste-masking technologies.
Controlled gas generation.
pH-buffered compositions.
Moisture-resistant packaging.
Direct-compression or multilayer tablets.
Specific tablet hardness, porosity, or dissolution profiles.

Such patents can remain relevant after expiration of the earlier platform patent if they have later priority dates and unexpired claims.

Drug-specific delivery patents

A later patent may claim an effervescent buccal or sublingual formulation of a specific active ingredient. These patents can create product-level barriers even though the broad platform patent has expired.

Manufacturing and packaging patents

Commercial barriers may also arise from:

Low-moisture granulation.
Segregated acid and base components.
Compression of moisture-sensitive tablets.
Foil or high-barrier blister packaging.
Stability-control systems.
Scale-up processes that preserve effervescence and tablet integrity.

These rights generally provide narrower but more commercially defensible protection than the broad method claim in U.S. 6,200,604.

How does U.S. Patent 6,200,604 compare with conventional oral and sublingual products?

Product type	Effervescent requirement	Oral-mucosal retention	Likely relationship
Conventional swallowed tablet	No	No	Generally outside claim 1
Standard effervescent tablet swallowed in water	Yes	No	Generally outside the claimed method
Sublingual non-effervescent tablet	No	Yes	Generally outside claim 1
Buccal bioadhesive effervescent tablet	Yes	Yes	Closest technical fit
Gingival effervescent tablet	Yes	Yes	Potential fit under claim 5
Oral dissolving tablet swallowed after dissolution	Not necessarily	No sustained retention	Weaker fit
Effervescent peptide buccal tablet	Yes	Yes	Potential fit under claims 1 and 9
pH-adjusted sublingual effervescent tablet	Yes	Yes	Potential fit under claims 2 and 4

The expired status makes this comparison relevant mainly for freedom-to-operate history, patent landscaping, and identification of later patents.

What generic launch risks exist today?

U.S. Patent 6,200,604 creates no current generic launch risk because it expired in 2018. The principal remaining risks would come from separate rights covering:

The active pharmaceutical ingredient.
A specific salt, polymorph, or prodrug.
A specific buccal or sublingual formulation.
Bioadhesive excipients.
A method of treating a named disease.
Dosage, duration, or patient-selection methods.
Manufacturing or packaging.
Regulatory exclusivity unrelated to this patent.

A generic applicant should not treat expiration of this patent as clearance for the entire product. The relevant freedom-to-operate question is product-specific and requires review of later-issued patents and regulatory exclusivities.

What revenue exposure is associated with the patent?

The patent itself has no remaining enforceable revenue exposure after expiration. Historical exposure would have depended on whether a commercial product used the claimed method and whether the patent was licensed or asserted before October 16, 2018.

No product, active ingredient, NDA, or sales figure is identified in the patent claims. A product-specific revenue estimate therefore cannot be derived from U.S. 6,200,604 alone.

Key Takeaways

U.S. Patent 6,200,604 claims a method of administering systemic drugs through the oral mucosa using a saliva-activated effervescent solid dosage form.
Claim 1 is broad in active ingredient and excipient selection but requires oral retention, effervescent activation, and increased transmucosal absorption.
Claims 2 through 7 cover pH adjustment, buccal, sublingual, gingival, bioadhesive, and conventional excipient embodiments.
Claims 8 and 9 extend the claimed drug genus to broad small-molecule categories and to peptides, proteins, and oligonucleotides.
Claims 10 through 12 add quantitative effervescent or gas-generation limitations.
The patent expired on October 16, 2018.
It has no current standalone Paragraph IV, Orange Book, biosimilar, or generic-launch blocking effect.
Later formulation, drug-specific, manufacturing, packaging, and method-of-use patents remain the relevant commercial barriers.
The patent document itself does not establish current licensing, litigation, settlement, or revenue obligations.

FAQs

Can an expired U.S. patent still affect freedom to operate?

Yes, indirectly. An expired patent can identify technical prior art, reveal formulation concepts, and help locate continuation or related patents. It cannot independently support an infringement injunction or block a current product.

Does an effervescent tablet infringe if the patient swallows it immediately?

The claimed method requires holding the dosage form and dissolving contents in the mouth while oral-mucosal absorption occurs. Immediate swallowing would generally not satisfy the full method.

Are peptides and proteins protected as products by claim 9?

No. Claim 9 is a dependent method claim. It does not claim peptides or proteins per se. It covers administering them through the claimed effervescent oral-mucosal method.

Could a later patent still block a buccal effervescent drug product?

Yes. A later patent may claim the specific active ingredient, formulation, excipient combination, dosing method, manufacturing process, or packaging system even though U.S. 6,200,604 has expired.

Is a bioadhesive required for all products within the patent?

No. Bioadhesion is required only for claim 6 and claims depending from it. Claim 1 does not expressly require a bioadhesive, although the product must still be held in the mouth and promote transmucosal absorption.

References

U.S. Patent and Trademark Office. (2001). U.S. Patent No. 6,200,604, Effervescent oral dosage forms. https://patents.google.com/patent/US6200604
U.S. Patent and Trademark Office. (2024). Patent Center. https://patentcenter.uspto.gov/
United States Code. (2024). 35 U.S.C. § 154: Contents and term of patent; provisional rights. https://www.law.cornell.edu/uscode/text/35/154
U.S. Food and Drug Administration. (2024a). Approved drug products with therapeutic equivalence evaluations, Orange Book. https://www.accessdata.fda.gov/scripts/cder/ob/
U.S. Food and Drug Administration. (2024b). Biosimilar and interchangeable biosimilar products. https://www.fda.gov/drugs/therapeutic-biologics-applications-bla/biosimilar-and-interchangeable-products

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	350017	⤷ Start Trial
Austria	433745	⤷ Start Trial
Austria	434432	⤷ Start Trial
Austria	548028	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Summary for Patent: 6,200,604