US Patent 6,310,101: Scope, Claims, Expiration, and Venlafaxine Patent Landscape

US Patent 6,310,101 covered the use of venlafaxine, desvenlafaxine-related compounds, and a broader chemical genus for treating panic disorder. The patent issued on October 30, 2001, from an April 9, 1999 U.S. filing claiming priority to April 9, 1998. Its 20-year patent term expired on April 9, 2019, absent any patent-term adjustment. The patent is therefore no longer an enforceable barrier to generic or branded treatment of panic disorder in the United States.

The commercially important species is venlafaxine, chemically identified in the patent as 1-[(2-dimethylamino)-1-(4-methoxyphenyl)ethyl]cyclohexanol. Claim 4 and several dependent claims expressly cover venlafaxine, its pharmaceutically acceptable salts, oral administration, daily doses, tablets, and capsules. The patent did not claim venlafaxine as a composition of matter. Its claims were limited to therapeutic use and related pharmaceutical compositions.

What does US Patent 6,310,101 cover?

US 6,310,101 is directed to methods of treating panic disorder with a class of substituted aminoalkyl cyclohexanol compounds. The patent’s central claim concept is the administration of an effective amount of a compound within a defined Markush formula to a mammal suffering from panic disorder.

The patent has three principal claim groups:

Claim group	Claims	Subject matter
Broad treatment claims	1-3	Treatment of panic disorder using a broad chemical genus
Compound-specific and dosage claims	4-7	Venlafaxine, a 4-hydroxy analog, and specified daily doses
Human and formulation claims	8-19	Human treatment, pharmaceutical compositions, oral administration, tablets, and capsules

The patent identifies the relevant compounds by structural formula rather than by generic name. The formula includes:

A substituted cyclohexanol core.
A dimethylaminoethyl or related aminoalkyl side chain.
An aryl group with permitted hydroxyl, alkoxy, halogen, alkyl, trifluoromethyl, and other substituents.
Optional unsaturation in the ring or side-chain structure.
Pharmaceutically acceptable salts.

The broad claims cover more compounds than venlafaxine. They include compounds with variations in the amino substituent, aryl substitution pattern, ring substitution, and degree of unsaturation.

Which claims specifically cover venlafaxine?

Claim 4 is the principal compound-specific claim for venlafaxine:

1-[(2-dimethylamino)-1-(4-methoxyphenyl)ethyl]cyclohexanol or a pharmaceutically acceptable salt thereof.

The patent’s venlafaxine-related claims are:

Claim	Limitation
4	Venlafaxine or a pharmaceutically acceptable salt
7	Claim 4 compound administered at approximately 75-200 mg/day
10	Human treatment with venlafaxine
11	Pharmaceutical composition containing venlafaxine and a carrier
16	Oral administration of venlafaxine
17	Oral pharmaceutical composition containing venlafaxine and a carrier
18	Tablet dosage form
19	Capsule dosage form

These claims are cumulative. For example, claim 19 requires a method of treating panic disorder in a human using a pharmaceutical composition containing venlafaxine and a carrier, with the composition in capsule form. A product that merely contains venlafaxine but is not used for panic disorder would not satisfy the full claim.

How broad are the Markush claims in US 6,310,101?

Claims 1 and 8 contain the broadest chemical scope. They cover a genus defined by multiple independently variable substituents.

The relevant variables include:

Variable	Claimed options
R1	Hydrogen or C1-C6 alkyl
R2	C1-C6 alkyl
R4	Hydrogen, C1-C6 alkyl, formyl, or C2-C7 alkanol
R5 and R6	Hydroxyl, alkyl, alkoxy, halo, trifluoromethyl, amino, nitro, cyano, acylamido, and related groups
R7	Hydrogen or C1-C6 alkyl
n	0, 1, 2, 3, or 4
Ring structure	Optional unsaturation
Salt form	Pharmaceutically acceptable salts

Claim 2 narrows these options, generally reducing the carbon-chain lengths and limiting aryl substituents to selected groups. Claim 3 narrows the substitution pattern and requires specified positioning of R5 and R6.

The broad genus is materially wider than venlafaxine. It could encompass multiple analogs, including compounds that differ from venlafaxine in aryl substitution, side-chain substitution, or ring structure. The commercial relevance of the broader claims was limited by their therapeutic-use requirement and by the patent’s expiration.

What compounds are expressly identified in the patent?

Two compounds are specifically recited.

Venlafaxine

Venlafaxine is the compound in claim 4:

Chemical name: 1-[(2-dimethylamino)-1-(4-methoxyphenyl)ethyl]cyclohexanol.
Common pharmaceutical form: venlafaxine hydrochloride.
Commercial product: Effexor and Effexor XR, historically marketed by Wyeth, now associated with Pfizer’s legacy product portfolio.
Pharmacology: serotonin-norepinephrine reuptake inhibitor.

The claims cover venlafaxine itself and pharmaceutically acceptable salts, including the hydrochloride salt used in commercial products.

4-Hydroxy analog

Claim 5 identifies:

1-[2-(dimethylamino)-1-(4-hydroxyphenyl)ethyl]cyclohexanol.

This structure corresponds to desvenlafaxine, also known as O-desmethylvenlafaxine, subject to the precise stereochemical and salt-form description used in the patent and later product records. Desvenlafaxine was later developed and marketed separately as Pristiq.

The patent’s claims therefore reach beyond the commercial venlafaxine product and include a therapeutically relevant active metabolite or related product candidate.

What dosage ranges are protected?

The patent recites two principal dosage ranges:

Claims	Dose limitation
6, 12, 14	Approximately 50-375 mg per day
7, 13, 15	Approximately 75-200 mg per day

The claims use dose limitations as additional narrowing elements. A method using a dose outside the claimed range would not literally satisfy a dosage-limited claim, although the broader treatment claims could still be relevant if their other limitations were met.

The claimed 75-200 mg/day range corresponds closely to conventional venlafaxine therapeutic dosing. Effexor XR labeling has historically described daily dosing ranges that overlap this range, although FDA-approved labeling is directed to approved indications such as major depressive disorder, generalized anxiety disorder, and social anxiety disorder rather than panic disorder.[1]

What formulations are protected by US 6,310,101?

Claims 9, 11, 17, 18, and 19 address pharmaceutical compositions and dosage forms. The formulation claims require:

Treatment of panic disorder in a human.
A composition containing the claimed compound.
A carrier.
In the case of claims 18 and 19, a tablet or capsule dosage form.

The patent does not claim a detailed controlled-release matrix, coating system, dissolution profile, particle-size distribution, or specific excipient combination. The formulation scope is therefore functional and relatively basic.

A conventional venlafaxine tablet or capsule could implicate the claims only when used in the claimed method of treating panic disorder. The claims do not independently cover every tablet or capsule containing venlafaxine for every indication.

Is US 6,310,101 a composition-of-matter patent?

No. US 6,310,101 is a method-of-treatment patent and a treatment-associated composition patent.

That distinction is central to its historical and current value:

It did not prevent manufacture of venlafaxine as a chemical compound after the composition-of-matter patent expired.
It did not independently block venlafaxine products labeled for indications outside panic disorder.
It required the claimed therapeutic use, and in some claims additional limitations such as human treatment, oral dosing, a carrier, or a tablet or capsule.
It expired in 2019.

The earlier venlafaxine composition-of-matter protection was associated with US Patent 4,535,186, which covered the compound itself. That earlier patent had a substantially broader product exclusionary effect but expired years before US 6,310,101.[2]

When did US Patent 6,310,101 expire?

The patent term expired on April 9, 2019, based on the April 9, 1999 U.S. filing date and the 20-year patent-term rule applicable to the application. The patent issued on October 30, 2001, as US 6,310,101 B1.

Event	Date
Priority date	April 9, 1998
U.S. filing date	April 9, 1999
Patent issue date	October 30, 2001
Patent term expiration	April 9, 2019
Current enforceability	Expired

The expiration date is determined from the effective U.S. filing date, not the issue date. Patent term adjustment can modify the ordinary 20-year calculation, but the public patent record identifies no commercially material extension that would preserve this patent today.[3]

What was the FDA and Orange Book status?

US 6,310,101 was not the principal Orange Book patent for venlafaxine products. The patent’s claimed indication, panic disorder, was not an approved indication for Effexor or Effexor XR in the FDA labeling used for generic substitution and regulatory review.

FDA-approved venlafaxine indications have included:

Major depressive disorder.
Generalized anxiety disorder.
Social anxiety disorder.

Panic disorder is distinct from generalized anxiety disorder and social anxiety disorder. A patent claiming panic-disorder treatment would not automatically qualify for Orange Book listing merely because it covers a use of the same active ingredient.

The Orange Book generally lists patents submitted by an NDA holder that claim the approved drug, a method of using the approved drug, or a method of manufacturing the approved drug, subject to FDA listing requirements. A method-of-use patent must correspond to an approved labeling use to create the standard use-code framework for an ANDA Paragraph IV certification.[4]

Because US 6,310,101 had expired by 2019 and was not the central patent listed for the approved venlafaxine indications, it presents no current Orange Book-based barrier to an ANDA applicant.

Were there Paragraph IV challenges involving this patent?

The principal Paragraph IV and ANDA litigation involving venlafaxine extended-release products focused on formulation and other listed patents, not on US 6,310,101.

Generic venlafaxine extended-release manufacturers challenged patents associated with Effexor XR, including patents directed to extended-release formulations and related product protection. Litigation included proceedings involving Wyeth and generic manufacturers such as Teva and other ANDA filers.[5]

US 6,310,101 had limited Paragraph IV relevance for several reasons:

It was a panic-disorder method patent.
Panic disorder was not the principal FDA-approved indication for venlafaxine products.
It expired in 2019.
A generic applicant could use a section viii statement to carve out a patented method when the FDA-approved labeling supported such a carve-out.
The patent’s claims did not independently cover the venlafaxine molecule or a specific extended-release technology.

No current Paragraph IV risk remains from this patent.

What patent litigation affected venlafaxine?

Venlafaxine patent litigation primarily concerned the extended-release version of Effexor XR. The commercial dispute involved generic entry, formulation patents, ANDA certifications, and the timing of generic launch.

The relevant litigation risk was historically concentrated in:

Risk area	Commercial effect
Extended-release formulation patents	Delayed or conditioned generic launch
Orange Book-listed product patents	Paragraph IV litigation exposure
Labeling and carve-out strategy	Ability to omit patented indications
Launch-at-risk decisions	Potential damages and injunction risk
Regulatory exclusivity	Separate from patent enforceability

US 6,310,101 was not the principal patent that protected the Effexor XR formulation. Its value was tied to the panic-disorder treatment method, not to the controlled-release delivery system.

What other patents were important in the venlafaxine landscape?

The relevant patent estate can be divided into four periods.

Patent category	Representative protection	Strategic significance
Composition of matter	US 4,535,186	Covered venlafaxine as a compound
Panic-disorder use	US 6,310,101	Covered treatment of panic disorder
Extended-release formulation	US 6,274,740 and related patents	Protected Effexor XR formulation technology
Desvenlafaxine product estate	US 6,673,838 and later patents	Supported separate development of Pristiq

US 4,535,186 is the key foundational venlafaxine patent. Its expiration opened the active-ingredient market. US 6,310,101 was a later use patent with narrower enforceability because it depended on the indication.

US 6,274,740 and related extended-release patents had greater commercial importance for Effexor XR because they addressed the product’s dosage form and release characteristics. Later desvenlafaxine patents were relevant to Pristiq rather than directly to generic venlafaxine.[2][6]

Patent-number and expiration analyses should be performed against the current USPTO Patent Center record, the FDA Orange Book, and the applicable patent-family documents because continuation applications, terminal disclaimers, and patent-term adjustments can change the effective scope of a portfolio.[3][4]

How strong was the patent estate for panic-disorder treatment?

The estate had moderate historical strength but weak current value.

Strengths

Claim 4 directly identifies venlafaxine.
Claims 10, 16, 18, and 19 target human, oral, tablet, and capsule use.
Claims 6, 7, and 12-15 provide dose-specific fallback positions.
Claims 8 and 9 separately address human treatment and pharmaceutical compositions.
The claims cover both venlafaxine and a 4-hydroxy analog.

Weaknesses

The claims are use-limited rather than composition-of-matter claims.
The patent did not block manufacture or sale of venlafaxine for non-panic indications.
The broad Markush claims could have faced prior-art, enablement, written-description, and claim-construction challenges.
The composition claims require therapeutic use and a carrier.
The patent expired in 2019.
The claimed indication was not the main FDA-approved venlafaxine labeling indication.

The strongest historical claims were claims 4, 10, and 16 because they focused on venlafaxine and human treatment. Claims 18 and 19 added dosage-form limitations but narrowed potential enforcement opportunities. The broadest claims, 1 and 8, had wider chemical coverage but were more exposed to disputes over the boundaries and support of the genus.

Does the patent create biosimilar risk?

No. Biosimilar law is not relevant to US 6,310,101 because venlafaxine and desvenlafaxine are small-molecule drugs, not biologics regulated under the Public Health Service Act.

The relevant competitive pathways are:

ANDAs for venlafaxine hydrochloride immediate-release products.
ANDAs for venlafaxine hydrochloride extended-release capsules.
New drug applications or 505(b)(2) applications for modified formulations or new clinical uses.
Conventional generic competition for desvenlafaxine products.

The principal regulatory and patent risks for a modified product would involve formulation patents, clinical bridging, labeling, and any still-active patents in the relevant product family, not biosimilar interchangeability.

Which companies challenged or competed with the branded products?

Generic venlafaxine competition has involved multiple manufacturers, including Teva and other ANDA applicants. The market has also included generic manufacturers supplying immediate-release and extended-release venlafaxine products after the relevant compound and formulation protections expired or were overcome.

The competitive landscape includes:

Pfizer and legacy Wyeth branded venlafaxine products.
Teva and other generic manufacturers.
Manufacturers of venlafaxine extended-release capsules.
Desvenlafaxine manufacturers competing with Pristiq.
Potential 505(b)(2) developers pursuing alternative release profiles or delivery systems.

Because US 6,310,101 expired in 2019, it does not differentiate current manufacturers based on panic-disorder use.

What licensing deals involved the patent?

The patent record identifies the original ownership history associated with American Home Products and its Wyeth successor, but US 6,310,101 is not generally recognized as the subject of a separate publicly disclosed licensing transaction.

The commercially important rights were developed within the Wyeth/American Home Products organization and later became part of Pfizer’s legacy portfolio through the acquisition of Wyeth. Publicly reported venlafaxine transactions have generally concerned product commercialization, corporate ownership, or generic settlement arrangements rather than a standalone license to US 6,310,101.

No current license can restore exclusivity after the patent’s expiration.

What generic launch scenarios existed?

Before expiration, generic entry could have followed several routes:

A generic applicant could market venlafaxine for approved indications that did not include panic disorder.
The applicant could use a section viii statement to carve out a patented panic-disorder method, where permitted by the approved labeling.
The applicant could challenge listed formulation patents through Paragraph IV certification.
A manufacturer could launch after expiration of the relevant composition and formulation patents.
A 505(b)(2) applicant could pursue a modified formulation or a new indication with separate patent exposure.

After April 9, 2019, US 6,310,101 no longer supports an injunction or damages claim for continuing conduct. Generic manufacturers can commercialize venlafaxine products without this patent creating a panic-disorder method barrier.

What geographic coverage did the patent have?

US 6,310,101 provided protection only in the United States. It did not establish patent rights in:

Canada.
The European Union.
Japan.
Australia.
Other jurisdictions.

Foreign protection would depend on corresponding national or regional applications in the patent family. Expiration dates could differ based on filing dates, prosecution delays, supplementary protection certificates, or local term rules. The U.S. expiration date does not establish the status of foreign family members.

Did the patent create manufacturing or IP barriers?

The patent created no current manufacturing barrier. It never directly claimed:

The venlafaxine molecule as such.
A synthetic route to venlafaxine.
A specific salt-manufacturing process.
A particular extended-release technology.
A specific tablet or capsule excipient system.

Its manufacturing relevance was indirect. A manufacturer selling venlafaxine for panic disorder during the patent term could have faced method-of-use exposure if the product, labeling, promotional conduct, or prescribing context supported infringement allegations. That risk ended with expiration.

Key Takeaways

US 6,310,101 is a panic-disorder method-of-treatment patent.
Claim 4 specifically covers venlafaxine and pharmaceutically acceptable salts.
Claim 5 covers a 4-hydroxy venlafaxine-related compound associated with desvenlafaxine.
Claims 6-7 and 12-15 cover daily doses ranging from approximately 50-375 mg/day and 75-200 mg/day.
Claims 16-19 address oral administration, carriers, tablets, and capsules.
The patent does not claim venlafaxine as a composition of matter.
The patent issued October 30, 2001, and expired April 9, 2019.
It was not the principal patent protecting Effexor XR’s extended-release technology.
Generic and Paragraph IV litigation involving venlafaxine focused primarily on formulation and product patents.
Biosimilar law does not apply.
The patent has no current blocking effect in the United States.
Current commercial risk lies in active formulation, process, product, or later-use patents, not US 6,310,101.

FAQs

What is the main active ingredient covered by US 6,310,101?

The main commercial compound is venlafaxine, specifically 1-[(2-dimethylamino)-1-(4-methoxyphenyl)ethyl]cyclohexanol and its pharmaceutically acceptable salts.

Did US 6,310,101 protect Effexor XR?

It protected a method of using the claimed compounds for panic disorder. It did not directly claim the extended-release delivery technology that defined Effexor XR.

Could a generic venlafaxine manufacturer omit panic disorder from its label?

During the patent term, a generic applicant could potentially use a section viii labeling carve-out if the FDA-approved labeling and patent listing supported that approach. The issue is no longer material for US 6,310,101 because the patent expired in 2019.

Is desvenlafaxine covered by the patent?

Claim 5 expressly recites a 4-hydroxy analog corresponding to desvenlafaxine-related chemistry. Separate patents and regulatory records govern the commercial desvenlafaxine product.

Can US 6,310,101 be asserted against a current venlafaxine product?

No. The patent expired on April 9, 2019, eliminating current infringement remedies based on the patent.

References

U.S. Food and Drug Administration. (2022). Effexor XR prescribing information. FDA.
United States Patent and Trademark Office. (1985). U.S. Patent No. 4,535,186, 1-[2-(dimethylamino)-1-(4-methoxyphenyl)ethyl]cyclohexanol. USPTO.
United States Patent and Trademark Office. (2001). U.S. Patent No. 6,310,101, treatment of panic disorder. USPTO.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
United States District Court for the District of Delaware. (2008-2013). Wyeth v. various ANDA applicants involving Effexor XR. PACER and reported federal court decisions.
United States Patent and Trademark Office. (2004). U.S. Patent No. 6,673,838, O-desmethyl venlafaxine. USPTO.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	213407	⤷ Start Trial
Austria	342715	⤷ Start Trial
Austria	392893	⤷ Start Trial
Australia	5831298	⤷ Start Trial
Australia	6592994	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,310,101

Summary for Patent: 6,310,101