United States Patent 8,242,131: Scope, Claims, Expiration, and Zolpidem Patent Landscape

U.S. Patent No. 8,242,131 protects post-awakening treatment of middle-of-the-night insomnia with low-dose zolpidem, particularly 3.0-3.75 mg for non-elderly patients and 1.5-2.5 mg for elderly patients. The claims focus on timing, patient age, dose, rapid absorption, oral-mucosal delivery, and the absence of residual sedation approximately four hours after dosing. The patent is associated with the Intermezzo sublingual zolpidem product and has a reported expiration date in March 2027, subject to the controlling patent-term calculation and any applicable terminal disclaimer or adjustment. (U.S. Patent No. 8,242,131, 2012; FDA, 2011)

What does U.S. Patent 8,242,131 protect?

The patent protects a method of treating a specific sleep disorder event rather than the general use of zolpidem for insomnia.

The core method requires:

A patient awakens during the night.
The patient wants to resume sleep for less than five hours.
Zolpidem is administered after that awakening.
The dose is low enough to permit awakening approximately four hours later without residual sedative effects.
The composition is substantially free of other hypnotic agents.

The patent has two principal independent claims:

Claim	Patient group	Zolpidem hemitartrate dose	Main method
1	Non-elderly patient	About 0.5-4.75 mg	Post-awakening treatment of middle-of-the-night insomnia
12	Elderly patient	About 1.5-2.5 mg	Post-awakening treatment of middle-of-the-night insomnia

The claims do not cover every zolpidem product or every insomnia treatment. They are directed to a particular dosing event, a limited remaining sleep period, and a low-dose pharmacokinetic and safety profile.

How broad is independent claim 1?

Claim 1 is the principal non-elderly-patient claim. Its numerical dose range is relatively broad, but its method limitations materially narrow the scope.

Claim 1 limitations

A potentially infringing method would need to satisfy each of the following limitations:

Treatment of middle-of-the-night insomnia.
A non-elderly patient.
No prophylactic administration of zolpidem.
Administration after the patient awakens from sleep.
The patient desires to resume sleep for less than five hours.
About 0.5-4.75 mg of zolpidem hemitartrate, or a molar-equivalent pharmaceutically acceptable form.
A composition substantially free of other hypnotic agents.
Ability to awaken approximately four hours after dosing without residual sedative effects.

The phrase “without prophylactically administering zolpidem” distinguishes the claimed method from taking zolpidem at bedtime to prevent an awakening. A product taken only after an actual nighttime awakening is much closer to the claim than a conventional bedtime zolpidem product.

The “less than five hours” limitation is commercially important. The FDA-approved Intermezzo labeling instructs patients to take the product only when at least four hours of sleep remain. The claim language uses a five-hour upper boundary, creating a zone in which the patent and approved product indication substantially overlap. (FDA, 2011)

How broad is independent claim 12 for elderly patients?

Claim 12 is narrower than claim 1 because it applies only to elderly patients and uses a lower dose range of approximately 1.5-2.5 mg zolpidem hemitartrate.

The claim reflects the lower recommended dose used for elderly or debilitated patients. In practical terms, a product labeled only for a 1.75 mg elderly dose may fall within the claim 12 family if the administration and sleep-timing conditions are met.

The claim does not require oral-mucosal delivery, a specific salt, or a particular excipient. Those limitations appear in dependent claims. A conventional immediate-release tablet could theoretically satisfy the broad method claim if it met the dose, timing, and functional-effect limitations, although the pharmacokinetic requirement and residual-sedation limitation would present proof issues.

What do the dependent claims add?

The dependent claims create narrower fallback positions around dose, delivery route, excipients, pharmacokinetics, and patient response.

Claims	Added limitation	Legal or commercial significance
2, 13	Resumption of sleep within 30 minutes	Adds an efficacy and timing limitation
3, 14	Approximately 50% of Cmax reached within 30 minutes or less	Adds a pharmacokinetic limitation
4	3.0-3.75 mg zolpidem hemitartrate	Targets the principal non-elderly dose range
5, 9, 10, 15, 19, 22, 24	Delivery across the oral mucosa	Captures sublingual or buccal delivery
6, 16	Salt form of zolpidem	Narrows the pharmaceutically acceptable form
7, 17	Sodium stearyl fumarate	Adds a formulation-excipient limitation
8, 22, 23	Approximately 3.5 mg zolpidem hemitartrate	Targets the higher Intermezzo strength
18, 24, 25	Approximately 1.75 mg zolpidem hemitartrate	Targets the lower Intermezzo strength
11, 20	Composition free of other hypnotic agents	Narrower than “substantially free”
21	Patient has normal capacity to metabolize zolpidem	Narrows patient characteristics

Claims 22-25 are especially important because they combine multiple limitations associated with a commercial sublingual product:

3.5 mg or 1.75 mg zolpidem hemitartrate;
salt form;
no other hypnotic agents;
oral-mucosal delivery;
sleep resumption within 30 minutes;
rapid attainment of approximately 50% Cmax.

These claims are narrower but may be easier to map onto product labeling, formulation data, and clinical pharmacology records.

What formulations are protected by U.S. Patent 8,242,131?

The patent does not claim a composition in the independent claims. It claims methods using a pharmaceutical composition.

The protected formulation characteristics include:

Zolpidem hemitartrate or an equivalent pharmaceutically acceptable zolpidem form.
Low-dose delivery.
Substantial absence of other hypnotic agents.
Optional sodium stearyl fumarate.
Optional delivery through the oral mucosa.
Rapid systemic exposure.

The oral-mucosal limitations in claims 5, 9, 10, 15, 19, 22, and 24 are relevant to sublingual tablets. A generic product that uses the same active ingredient and dose but relies exclusively on gastrointestinal absorption may avoid those dependent claims while remaining exposed to the broader independent claims, depending on its pharmacokinetics and labeled method of use.

Sodium stearyl fumarate is a formulation-specific limitation. A competing product that uses a different lubricant or tableting aid would not satisfy that limitation literally. It could still face the independent claims because those claims do not require sodium stearyl fumarate.

What is the Orange Book status of zolpidem sublingual products?

Intermezzo was approved by the FDA as a low-dose sublingual zolpidem tartrate product for middle-of-the-night awakening when the patient has at least four hours remaining before planned awakening. The product was approved in 1.75 mg and 3.5 mg strengths. (FDA, 2011)

The patent is associated with the Intermezzo patent estate and has been treated as a method-of-use patent relevant to abbreviated new drug applications. The Orange Book analysis should distinguish:

the NDA product and its listed patents;
the patent expiration date;
the FDA use code;
whether an ANDA applicant carves out the protected use;
whether the applicant certifies under Paragraph IV;
whether litigation triggers a 30-month stay.

Orange Book listing does not establish that every claim is valid or infringed. It gives the NDA holder a statutory framework to assert listed patents against an ANDA applicant. (FDA, 2024; 21 U.S.C. § 355)

When does U.S. Patent 8,242,131 lose exclusivity?

The reported patent-term date is March 17, 2027, based on the patent family’s priority and filing history. The controlling expiration date should be confirmed against the USPTO patent record and any terminal disclaimer or patent-term adjustment.

Milestone	Date or status
Earliest reported priority	March 17, 2006
Patent issued	August 14, 2012
FDA approval of Intermezzo	November 2011
Reported patent expiration	March 17, 2027
Earliest ordinary post-expiration generic entry	Potentially March 2027, subject to other patents, regulatory exclusivity, litigation, and settlement terms

The patent does not create a new monopoly over zolpidem itself. Basic zolpidem compound protection is substantially older. The commercial value lies in the low-dose, post-awakening, sublingual use case.

Which companies own or commercialize the relevant rights?

The patent was issued to Transcept Pharmaceuticals, Inc., the company associated with the development of Intermezzo. Intermezzo rights and related commercial assets later became associated with Purdue Pharma entities through corporate transactions and product-rights arrangements.

The relevant commercial parties have included:

Transcept Pharmaceuticals, Inc.;
Purdue Pharma and affiliated entities;
FDA-approved generic applicants and manufacturers seeking abbreviated approval for zolpidem sublingual tablets.

The exact patent owner, assignee, and NDA holder should be separated in diligence. Patent ownership, NDA ownership, commercial distribution rights, and litigation control can reside in different corporate entities.

What patent litigation affects Intermezzo and zolpidem sublingual products?

The principal litigation risk arises from ANDA applicants seeking approval for generic 1.75 mg or 3.5 mg zolpidem sublingual tablets.

A Paragraph IV challenge could assert that the patent is:

invalid for lack of novelty;
obvious in view of prior zolpidem dosing and sublingual-delivery references;
inadequately described or enabled;
not infringed because the proposed product does not satisfy the method limitations;
not infringed because the ANDA label omits the protected middle-of-the-night use.

For this patent, an infringement case would likely focus on the proposed label and the relationship between label instructions and the asserted claims. The strongest evidence for the patent holder would be:

a label instructing use after nighttime awakening;
1.75 mg and 3.5 mg strengths;
sublingual administration;
at least four hours of remaining sleep;
clinical or pharmacokinetic data showing rapid exposure.

The strongest defenses would involve:

an ANDA label that omits the patented use;
a product not delivering zolpidem across the oral mucosa;
dose ranges outside the asserted claim;
absence of evidence for the four-hour residual-effect limitation;
invalidity based on prior art showing low-dose zolpidem or rapid sublingual absorption.

The statute governing ANDA patent certifications and associated litigation is section 505(j) of the Federal Food, Drug, and Cosmetic Act. A Paragraph IV notice can trigger patent litigation and, in the ordinary case, a 30-month stay of final FDA approval if suit is timely filed. (21 U.S.C. § 355)

How strong is the patent estate for Intermezzo?

The estate is strongest against a generic that closely copies the approved product profile.

Strong infringement position

Risk is highest when a generic has:

1.75 mg and 3.5 mg sublingual tablets;
labeling for awakening during the night;
instructions to take the product only when several hours of sleep remain;
zolpidem tartrate or hemitartrate;
rapid systemic absorption;
the same or similar clinical-use instructions as Intermezzo.

Moderate infringement position

Risk is more mixed when a product:

uses the same strengths but a different delivery route;
has an ANDA label omitting oral-mucosal delivery;
provides no express instruction for post-awakening use;
has different pharmacokinetics;
relies on a different formulation technology.

Lower infringement position

Risk is lower where a product:

is a conventional bedtime zolpidem tablet;
is labeled only for initiation of sleep;
contains a materially different dose;
does not target middle-of-the-night awakening;
has no approved sublingual or buccal administration.

Validity risk is more substantial for the broad method claims than for the narrow combination claims. The broad claims use functional language such as “permits” awakening without residual sedative effects and “about” numerical ranges. Narrow claims 22-25 have more elements, which may improve validity but make infringement more difficult to prove.

What generic launch scenarios exist?

Scenario 1: No successful Paragraph IV challenge

If the patent remains enforceable through its term and no settlement permits an earlier launch, a close-copy generic faces potential entry delay until the patent-term date in March 2027.

Scenario 2: Label carve-out

A generic applicant may attempt to omit the middle-of-the-night indication from its labeling. This could reduce induced-infringement exposure, but a carve-out is difficult if the product’s only commercial value is the patented use and the remaining label would not support meaningful marketing.

Scenario 3: Litigation settlement

A settlement could establish an agreed launch date before March 2027, subject to antitrust review and the terms of any license, supply arrangement, or authorized-generic deal. Settlement terms may also address pediatric rights, manufacturing, distribution, or non-infringing formulations.

Scenario 4: Invalidity or non-infringement judgment

A successful challenge could permit approval and launch before the reported expiration date, subject to other listed patents and regulatory exclusivity.

Does biosimilar risk apply to zolpidem?

No. Zolpidem is a small-molecule chemical drug, not a biologic. The relevant competitive pathway is an ANDA under section 505(j), not a biosimilar application under section 351(k) of the Public Health Service Act.

Competitive threats therefore come from:

generic zolpidem sublingual tablets;
alternative immediate-release zolpidem products;
other hypnotics for sleep-maintenance insomnia;
digital and behavioral insomnia therapies;
products using different delivery systems.

How does this patent compare with other zolpidem patent categories?

Patent category	Subject matter	Relevance to 8,242,131
Compound patents	Zolpidem molecule or core chemical structure	Generally older and less relevant to current Intermezzo entry
Conventional tablet patents	Oral zolpidem compositions	May not cover sublingual use
Sublingual formulation patents	Tablet composition, disintegration, absorption, excipients	Can create separate formulation barriers
Method-of-use patent 8,242,131	Low-dose post-awakening treatment	Directly targets Intermezzo’s clinical use
Labeling and regulatory rights	NDA approval, listed use codes, exclusivity	Determines practical ANDA approval risk
Manufacturing patents	Granulation, compression, coating, or excipient processing	Can restrict manufacturing methods but often has narrower commercial reach

The commercial patent risk is cumulative. A generic may defeat or design around one patent but still face another formulation or method-of-use patent.

What revenue exposure is associated with patent expiration?

The patent protects a narrow product category rather than the entire zolpidem market. Revenue exposure depends on:

Intermezzo sales at the time of generic entry;
the percentage of sales attributable to the 1.75 mg and 3.5 mg strengths;
whether generic applicants launch both strengths;
the number of approved ANDA competitors;
payer substitution and formulary placement;
the availability of conventional zolpidem and alternative hypnotics.

Generic entry would likely apply significant price pressure because the product is a small-molecule oral dosage form. The protected clinical niche may limit total market size, but the sublingual delivery and low-dose strengths make direct substitution relatively straightforward if a generic receives approval.

Key Takeaways

U.S. Patent 8,242,131 is a method-of-use patent for low-dose zolpidem treatment after middle-of-the-night awakening.
Claims 1 and 12 divide protection between non-elderly and elderly patients.
The principal claimed doses are approximately 3.5 mg for non-elderly patients and 1.75 mg for elderly patients.
Oral-mucosal delivery, rapid attainment of approximately 50% Cmax, sleep resumption within 30 minutes, and absence of residual sedation are dependent limitations.
The patent is closely aligned with the Intermezzo 1.75 mg and 3.5 mg sublingual products.
The reported expiration date is March 17, 2027.
Generic risk centers on Paragraph IV challenges, label carve-outs, and formulation or method-of-use design-arounds.
Biosimilar risk does not apply because zolpidem is a small-molecule drug.
The strongest patent position is against a generic that copies the Intermezzo label, dose strengths, sublingual route, and middle-of-the-night indication.
The broad claims face greater validity and claim-construction exposure than the narrower combination claims.

FAQs About U.S. Patent 8,242,131

Does U.S. Patent 8,242,131 cover all zolpidem products?

No. It covers specified methods of using low-dose zolpidem after a nighttime awakening. Conventional bedtime zolpidem products generally fall outside the claimed method unless their labeling and use satisfy the claim limitations.

Does the patent require sublingual administration?

No. The independent claims do not require oral-mucosal delivery. Sublingual or oral-mucosal delivery appears in dependent claims and is central to the Intermezzo product profile.

Is a 1.75 mg zolpidem product exposed to this patent?

Potentially yes. A 1.75 mg product may fall within claims 18, 24, and 25 if it is used by an elderly patient after awakening, is free of other hypnotics, delivers zolpidem across the oral mucosa, and satisfies the sleep-response and pharmacokinetic limitations.

Can a generic avoid the patent by omitting the middle-of-the-night indication?

Possibly, but the effectiveness of a label carve-out depends on the remaining approved uses, the product’s commercial purpose, and whether other conduct supports induced infringement.

Is sodium stearyl fumarate required for infringement?

No. Sodium stearyl fumarate is required only for claims 7 and 17. A product without that excipient may still be exposed to independent claims or other dependent claims.

References

Food and Drug Administration. (2011). Intermezzo (zolpidem tartrate) sublingual tablets, prescribing information. U.S. Department of Health and Human Services.

Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. U.S. Department of Health and Human Services.

U.S. Patent No. 8,242,131. (2012). Methods of treating insomnia. United States Patent and Trademark Office.

United States Code. (2024). 21 U.S.C. § 355: New drugs. U.S. Government Publishing Office.

United States Code. (2024). 35 U.S.C. §§ 101, 102, 103, 112, and 271. U.S. Government Publishing Office.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Purdue Pharma	INTERMEZZO	zolpidem tartrate	TABLET;SUBLINGUAL	022328-001	Nov 23, 2011		DISCN	Yes	No	⤷ Start Trial	⤷ Start Trial				METHOD OF TREATING MIDDLE-OF-THE-NIGHT INSOMNIA	⤷ Start Trial
Purdue Pharma	INTERMEZZO	zolpidem tartrate	TABLET;SUBLINGUAL	022328-002	Nov 23, 2011		DISCN	Yes	No	⤷ Start Trial	⤷ Start Trial				METHOD OF TREATING MIDDLE-OF-THE-NIGHT INSOMNIA	⤷ 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
Australia	2006249761	⤷ Start Trial
Brazil	PI0609984	⤷ Start Trial
Canada	2609330	⤷ Start Trial
China	101198327	⤷ Start Trial
European Patent Office	1883408	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,242,131

Which drugs does patent 8,242,131 protect, and when does it expire?

Summary for Patent: 8,242,131