United States Patent 6,919,092: Oxybutynin Extended-Release Scope, Claims, Expiration, and Patent Landscape

United States Patent 6,919,092 covers oral oxybutynin dosage forms designed to release oxybutynin over approximately 24 hours, including formulations with substantially zero-order release, specified oxybutynin plasma exposure, hydroxycellulose excipients, and tablet dosage forms. The patent was directed primarily to the technology commercialized in Ditropan XL extended-release tablets. Its ordinary patent term ended on July 16, 2019, and it no longer creates an enforceable U.S. patent barrier to generic oxybutynin extended-release products.[1][2]

The patent’s strongest claim concepts were the combination of:

A 24-hour oral delivery period;
Controlled or substantially zero-order release;
Oxybutynin hydrochloride or another pharmaceutically acceptable oxybutynin salt;
A defined maximum plasma oxybutynin concentration; and
Optional hydroxycellulose matrix excipients.

What does United States Patent 6,919,092 cover?

Patent 6,919,092 covers oxybutynin controlled-release dosage forms and methods for treating urinary incontinence. The claims are composition, dosage-form, pharmacokinetic, and method-of-treatment claims.

The patent does not broadly claim every oxybutynin product. A potentially infringing product would generally need to satisfy the relevant claim limitations, including the amount of oxybutynin, release duration, release profile, pharmacokinetic result, dosage form, or method of use.

Patent identification

Item	Information
Patent	U.S. Patent No. 6,919,092
Title	Oxybutynin pharmaceutical compositions and methods of use
Technology	Oral controlled-release oxybutynin
Active ingredient	Oxybutynin and pharmaceutically acceptable salts
Principal salt	Oxybutynin hydrochloride
Dosage form	Primarily an oral tablet
Release duration	Approximately 24 hours
Release profile	Controlled, sustained, and in several claims substantially zero-order
Assignee associated with the patent estate	ALZA Corporation
Issued	2005
Patent term endpoint	July 16, 2019
Current U.S. enforceability	Expired

The claims are directed to the product characteristics and resulting pharmacokinetic profile rather than to a single narrowly defined manufacturing process.

How do the 23 claims divide by claim category?

The claims form several related groups.

Claims	Claim type	Core limitation
1	Method of treatment	Oral oxybutynin dosage form, 24-hour controlled release, 0.05 to 0.850 mg/hour
2	Dosage form	240 ng to 650 mg oxybutynin, 24-hour substantially zero-order release
3	Dosage form	5 mg to 250 mg, specified maximum plasma concentration per milligram, 24-hour delivery
4	Dependent composition	Oxybutynin hydrochloride
5, 8	Release profile	Substantially zero-order release
6, 7	Excipient limitation	Selected hydroxycellulose polymers
9-12	Dosage-form limitation	Tablet
13	Method of treatment	Same pharmacokinetic and 24-hour delivery limitations as claim 3
14-15, 17	Dependent method claims	Oxybutynin hydrochloride and hydroxycellulose excipients
16, 18	Release profile	Substantially zero-order release
19-22	Dosage-form limitation	Tablet
23	Therapeutic-result limitation	Reduced incidence of oxybutynin-associated side effects

Claims 1 and 2: release-rate claims

Claim 1 requires administration of a dosage form containing 240 ng to 650 mg of oxybutynin or its salt. The dosage form must release the active ingredient at a controlled and sustained, substantially zero-order rate of 0.05 mg/hour to 0.850 mg/hour for approximately 24 hours.

Claim 2 is a product claim with a similar broad quantity range and a 24-hour substantially zero-order release requirement. It does not expressly include the numerical release-rate range appearing in claim 1.

The practical scope is directed to an oral extended-release system that maintains a relatively steady delivery rate. Immediate-release tablets, twice-daily products, transdermal systems, and formulations with materially nonuniform release would generally fall outside these claims unless they nevertheless satisfy all express limitations.

Claims 3 and 13: pharmacokinetic claims

Claims 3 and 13 are important because they do not rely only on in vitro dissolution behavior. They require:

A dosage form containing 5 mg to 250 mg of oxybutynin or a pharmaceutically acceptable salt;
A maximum plasma oxybutynin concentration of approximately 0.28 ng/mL to 0.45 ng/mL per milligram of oxybutynin in the dosage form; and
Delivery over approximately 24 hours.

These claims attempt to capture a clinically relevant exposure profile. A formulation could therefore face claim risk even if its excipients or manufacturing process differed from the disclosed examples, provided the product produced the claimed dose-normalized maximum plasma concentration and 24-hour delivery period.

The pharmacokinetic limitation also creates enforcement complexity. Infringement would require reliable testing of the accused product and a defensible interpretation of:

The phrase “maximum plasma oxybutynin concentration”;
Dose normalization on a per-milligram basis;
The meaning of “about”;
The patient population and study conditions;
The analytical method; and
Whether the claimed concentration must be achieved consistently across subjects.

Claims 6, 7, 15, and 17: hydroxycellulose excipients

These claims narrow the formulation to a dosage form containing one or more selected cellulose ethers:

Hydroxypropylmethylcellulose;
Hydroxypropylethylcellulose;
Hydroxypropylbutylcellulose; or
Hydroxypropylpentylcellulose.

The excipient claims are formulation-specific. They would not cover every controlled-release oxybutynin formulation, particularly one using a different rate-controlling polymer, osmotic system, lipid matrix, multiparticulate system, or coating technology.

Hydroxypropylmethylcellulose, commonly known as hypromellose or HPMC, is widely used in extended-release tablets. Its presence alone would not establish infringement. The accused product would also need to satisfy the relevant oxybutynin dose, release-duration, release-profile, and, where applicable, pharmacokinetic limitations.

Claim 23: reduced side effects

Claim 23 depends on method claim 13 and requires reduced incidence of side effects associated with oxybutynin treatment. This limitation is narrower than the underlying 24-hour delivery claim.

The claim raises several legal and evidentiary issues:

The claimed reduction must be tied to the claimed dosage form;
“Side effects associated with oxybutynin treatment” is broader than a single adverse event;
The comparison treatment and statistical standard would matter;
The result may be difficult to prove from a product label alone; and
A generic applicant might dispute whether the product label induces the claimed method.

Claim 23 is not a standalone composition claim. It depends on claim 13 and inherits that claim’s dose, pharmacokinetic, and 24-hour delivery limitations.

What formulation technology is protected?

The patent protects the performance characteristics of an extended-release oxybutynin dosage form more directly than a single manufacturing design.

Relevant protected concepts include:

Oral delivery for approximately 24 hours;
Controlled and sustained release;
Substantially zero-order release;
Dose-normalized oxybutynin maximum plasma concentration;
Oxybutynin hydrochloride;
Hydroxycellulose matrix excipients; and
Tablet dosage forms.

The claim language is broad enough to reach more than one physical architecture. A formulation using a hydrophilic matrix, coating, osmotic mechanism, or combination system could potentially fall within the claims if it produced the specified release and pharmacokinetic results.

The claims do not expressly require the ALZA OROS osmotic-pump technology used in the commercial Ditropan XL product. This distinction matters. A competing product could avoid an architecture-specific claim while still presenting risk under a performance-based claim. Conversely, a product could use a similar controlled-release concept but avoid infringement if it did not satisfy the numerical plasma concentration or release-rate limitations.

How does Patent 6,919,092 compare with related oxybutynin patents?

The U.S. oxybutynin extended-release estate included earlier patents directed to controlled-release compositions and related delivery technology.

Patent	General subject matter	Relationship to U.S. 6,919,092
U.S. 5,718,706	Controlled-release oxybutynin compositions	Earlier foundational controlled-release patent
U.S. 6,419,960	Oxybutynin compositions and delivery characteristics	Closely related patent in the same commercial estate
U.S. 6,919,092	Oxybutynin dosage forms, pharmacokinetics, 24-hour delivery, and side-effect reduction	Later patent with overlapping product-performance concepts

U.S. Patent 5,718,706 was associated with the earlier controlled-release formulation estate and reached the end of its ordinary term before Patent 6,919,092. U.S. Patent 6,419,960 and Patent 6,919,092 had overlapping commercial relevance to Ditropan XL and its generic competition.[1][3]

The estate should be analyzed as a layered portfolio:

Foundational controlled-release composition claims;
Product-performance and pharmacokinetic claims;
Specific excipient and tablet claims;
Method-of-use claims; and
Commercial-product regulatory listings.

The expiration of one patent did not necessarily eliminate all risk while related patents remained in force. That layered risk has now largely converted into historical rather than current freedom-to-operate risk because the principal U.S. patents have expired.

What was the FDA and Orange Book status?

Ditropan XL is an extended-release oxybutynin chloride product approved by the FDA for symptoms of urinary urgency, frequency, and urge incontinence associated with overactive bladder.[4]

The FDA Orange Book listed patents associated with Ditropan XL, including U.S. Patent Nos. 5,718,706, 6,419,960, and 6,919,092. Orange Book listings functioned as the basis for abbreviated new drug application certification and associated regulatory litigation. They did not independently determine patent validity or infringement.[1][5]

Regulatory significance

A generic applicant seeking approval for oxybutynin chloride extended-release tablets could use an ANDA pathway if it demonstrated pharmaceutical equivalence and bioequivalence to the reference listed drug. The applicant could certify that:

No patent information had been submitted;
The listed patent had expired;
The applicant would wait for patent expiration; or
The patent was invalid, unenforceable, or would not be infringed under a Paragraph IV certification.

A Paragraph IV certification could trigger patent litigation under the Hatch-Waxman framework. The 30-month stay mechanism depended on timely suit by the listed patent owner or NDA holder and the applicable regulatory record.[6]

Which companies challenged the oxybutynin extended-release patents?

The Ditropan XL patent estate was challenged in ANDA litigation involving generic manufacturers, including Mylan and other ANDA applicants. Reported litigation involving ALZA’s oxybutynin controlled-release patents addressed infringement, validity, claim construction, and the scope of the controlled-release technology.[3]

The litigation history is commercially relevant for two reasons:

The principal disputes concerned whether generic controlled-release formulations practiced the claimed release characteristics; and
The outcomes affected the timing of generic entry before patent expiration.

The record should not be reduced to a simple “patent upheld” or “patent invalidated” conclusion. The relevant patents had different claims, prosecution histories, and litigation outcomes. A claim-by-claim analysis is necessary because a decision concerning one patent or one ANDA formulation does not automatically determine the status of Patent 6,919,092.

When did Patent 6,919,092 lose exclusivity?

Patent 6,919,092 reached the end of its ordinary U.S. patent term on July 16, 2019.[2] Any applicable pediatric exclusivity would have extended the regulatory protection period only if granted and associated with the relevant product. The patent itself is now expired.

The commercial exclusivity timeline was therefore:

Period	Commercial significance
Before generic approval	Ditropan XL protected by branded approval, formulation patents, and Orange Book litigation risk
During Paragraph IV litigation	Potential 30-month regulatory stay and delayed ANDA approval
After earlier patent expirations	Reduced estate coverage, but remaining listed patents could continue to delay entry
After July 16, 2019	Patent 6,919,092 no longer blocked U.S. generic launch

FDA approval of a generic does not itself prove that every claim of Patent 6,919,092 was invalid. It reflects the regulatory pathway and the applicant’s certifications, litigation posture, or the expiration of relevant listed patents.

What generic launch risks existed?

Before expiration, generic entry risk depended on the product’s release mechanism and clinical profile.

Main risk factors

A generic oxybutynin extended-release product faced higher historical risk if it:

Used a 24-hour tablet;
Produced substantially zero-order release;
Used oxybutynin hydrochloride;
Used HPMC or a similar hydroxycellulose matrix;
Produced a dose-normalized maximum plasma concentration within the claimed range;
Used labeling that encouraged treatment of urge incontinence or overactive bladder; or
Was shown to reduce anticholinergic side effects relative to immediate-release oxybutynin.

A generic product faced lower risk under Patent 6,919,092 if it:

Used a different dosing interval;
Did not deliver oxybutynin for approximately 24 hours;
Produced a materially different plasma concentration profile;
Avoided the claimed excipient where the dependent claim was at issue; or
Could not satisfy the substantially zero-order limitation.

These distinctions did not eliminate risk under other patents, regulatory requirements, or different infringement theories.

How strong is the patent estate?

During its term, Patent 6,919,092 had meaningful commercial relevance because it combined broad product-performance concepts with specific pharmacokinetic limitations. The strongest aspects were:

Coverage of the commercial 24-hour extended-release concept;
Claims tied to measurable plasma exposure;
Multiple dependent claims covering oxybutynin hydrochloride, hydroxycellulose excipients, and tablets;
Method claims aligned with the approved therapeutic use; and
Position within a broader ALZA oxybutynin patent portfolio.

The main vulnerabilities were:

Potential prior-art challenges involving earlier controlled-release oxybutynin systems;
Ambiguity in terms such as “about,” “substantially zero order,” and “over a period of about 24 hours”;
Difficulty proving pharmacokinetic infringement across patient populations;
Potential enablement or written-description issues for broad dose and release-rate ranges; and
The functional nature of several limitations.

The estate is now commercially weak as a blocking portfolio because Patent 6,919,092 has expired. Its technical disclosure remains relevant for formulation design, patent landscaping, and validity analysis of later oxybutynin patents.

Does biosimilar risk apply to oxybutynin?

No. Oxybutynin is a small-molecule drug, not a biologic. Biosimilar approval under the Public Health Service Act is not the applicable pathway. Competition proceeds through generic-drug mechanisms, principally ANDAs under section 505(j) of the Federal Food, Drug, and Cosmetic Act.[6]

The relevant competitive issues are:

ANDA approval;
Pharmaceutical equivalence;
Bioequivalence;
Paragraph IV certifications;
Orange Book patent listings;
Formulation differentiation; and
Manufacturing capability for controlled-release tablets.

What is the current commercial impact?

Patent 6,919,092 has no remaining blocking value against new U.S. oxybutynin extended-release products. Revenue exposure from the patent was concentrated in the Ditropan XL franchise and related generic-entry timing.

Current commercial competition is determined by:

Generic oxybutynin extended-release availability;
Brand recognition and payer positioning;
Product shortages or manufacturing discontinuity;
Therapeutic substitution with other overactive-bladder treatments;
Newer antimuscarinic or beta-3 agonist products; and
The ability to manufacture a stable 24-hour dosage form at commercial scale.

The key manufacturing barrier is formulation reproducibility, not live exclusion under Patent 6,919,092. Controlled-release products must maintain dissolution performance, content uniformity, stability, and bioequivalence across production lots.

Key Takeaways

U.S. Patent 6,919,092 covers 24-hour oral oxybutynin delivery, substantially zero-order release, specified pharmacokinetic exposure, hydroxycellulose excipients, tablets, and incontinence-treatment methods.
Claims 3 and 13 are the principal pharmacokinetic claims and require a dose-normalized maximum plasma oxybutynin concentration of approximately 0.28 to 0.45 ng/mL per milligram.
Claims 6, 7, 15, and 17 narrow coverage to specified hydroxycellulose excipients.
Claim 23 adds a reduced-side-effect limitation to the method-of-treatment category.
The patent was part of the ALZA/Ditropan XL controlled-release oxybutynin estate.
Related U.S. patents included Nos. 5,718,706 and 6,419,960.
The patent expired on July 16, 2019.
Paragraph IV litigation and Orange Book listings were historically important, but Patent 6,919,092 no longer blocks U.S. generic entry.
Oxybutynin competition is governed by generic-drug law, not biosimilar law.
Current risk is primarily technical and regulatory: bioequivalence, dissolution performance, manufacturing consistency, and any later or unrelated patent rights.

FAQs

What drug product was most closely associated with U.S. Patent 6,919,092?

The patent was closely associated with Ditropan XL, an extended-release oxybutynin chloride product for overactive bladder and urge incontinence.

Does using oxybutynin hydrochloride alone infringe Patent 6,919,092?

No. Oxybutynin hydrochloride is only one limitation in certain dependent claims. Infringement would require satisfaction of the other applicable dose, release, duration, dosage-form, or pharmacokinetic limitations.

Can a non-tablet oxybutynin product fall within the patent claims?

Yes, potentially. The independent claims are not all limited to tablets. Claims 9 through 12 and 19 through 22 expressly add tablet limitations, but claims 1 through 3 and 13 are broader in dosage-form structure.

Does a different release mechanism avoid the patent?

Not necessarily. The claims focus heavily on release performance and pharmacokinetic results. A different mechanism could still fall within a claim if it met the express limitations.

Can Patent 6,919,092 support a current U.S. patent-infringement suit?

No. The patent’s ordinary term ended on July 16, 2019. It can remain relevant as prior art and as part of the historical Orange Book and litigation record, but it does not provide current exclusionary rights.

References

United States Patent and Trademark Office. (2005). U.S. Patent No. 6,919,092, Oxybutynin pharmaceutical compositions and methods of use.
United States Patent and Trademark Office. (n.d.). Patent term adjustment and patent expiration information for U.S. Patent No. 6,919,092.
United States Court of Appeals for the Federal Circuit. (2004). Alza Corp. v. Mylan Laboratories, Inc., 391 F.3d 1365.
U.S. Food and Drug Administration. (n.d.). Ditropan XL prescribing information.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book.
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application process and Paragraph IV patent certifications.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	5639296	⤷ Start Trial
Australia	695194	⤷ Start Trial
Australia	718849	⤷ Start Trial
Australia	9052298	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,919,092

Summary for Patent: 6,919,092