United States Patent 4,409,212: Scope, Claims, Expiration, and Patent Landscape

U.S. Patent No. 4,409,212 covers oral or rectal administration of specified dibenzazepine carboxamides to prevent or treat impaired memory, including senile dementia, multi-infarction dementia, and Alzheimer’s dementia. The principal compounds are carbamazepine, oxcarbazepine, and 10-hydroxy carbamazepine. The patent issued in 1983 and its ordinary U.S. patent term expired in 2000. It does not create current U.S. exclusivity for these compounds, dementia treatment, epilepsy products, or generic manufacturers.

What does U.S. Patent 4,409,212 claim?

The patent claims a therapeutic method, not a new compound, pharmaceutical composition, formulation, manufacturing process, or diagnostic method.

The independent claim requires four elements:

A human patient with an impaired memory condition.
Oral or rectal administration.
A prophylactically or therapeutically effective amount.
A compound within the claimed dibenzazepine-carboxamide formula.

Claim 1 is a Markush-type method claim. It covers compounds defined by alternative substituent relationships represented by X1, X2, and Y. The alternatives include:

A compound with an additional bond between X2 and Y, where X1 is hydrogen, fluorine, chlorine, bromine, or cyano.
A 10-oxo compound, where X1 and X2 together form an oxo group and Y is hydrogen.
A 10-hydroxy compound, where X1 is hydroxy and X2 and Y are hydrogen.

The halogen limitation "having an atomic number up to 35" reaches fluorine, chlorine, and bromine. It does not reach iodine, which has an atomic number of 53.

The claim language supplied does not reproduce the structural formula image. Exact infringement analysis for every Markush member therefore depends on the formula and atom numbering in the issued patent. The named species in claims 4 through 6 provide the clearest scope.

Which drugs are expressly covered by U.S. Patent 4,409,212?

Patent claim	Chemical name	Common name or related name	Commercial relevance
Claim 4	5H-dibenz[b,f]azepine-5-carboxamide	Carbamazepine	Generic anticonvulsant and neuralgia product
Claim 5	10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine-5-carboxamide	Oxcarbazepine	Trileptal and generic oxcarbazepine
Claim 6	10,11-dihydro-10-hydroxy-5H-dibenz[b,f]azepine-5-carboxamide	10-hydroxy carbamazepine, licarbazepine-related compound	Active metabolite and stereochemical variants associated with eslicarbazepine products

Carbamazepine is the direct compound in claim 4. Oxcarbazepine is the direct compound in claim 5. Claim 6 is directed to the corresponding 10-hydroxy derivative.

Eslicarbazepine acetate is not automatically covered by claim 6. Eslicarbazepine acetate is an acetate prodrug, while claim 6 identifies the free 10-hydroxy carboxamide. Patent scope cannot be extended from the free alcohol to its acetate ester without a claim-construction basis in the issued formula or an applicable doctrine of equivalents analysis.

How do the dependent claims narrow the patent scope?

Claim 2: disease limitation

Claim 2 narrows the impaired-memory indication to:

Senile dementia.
Multi-infarction dementia.
Alzheimer’s dementia.

A product or use outside those named conditions may still fall under claim 1 if it treats an impaired memory condition, but it would not fall under claim 2 unless the condition satisfies the claim’s disease limitation.

Claim 3: preferred substituents

Claim 3 limits X1 to:

Hydrogen.
Chlorine.
Cyano.

It excludes bromine and other halogen alternatives that may fall within claim 1.

Claims 4 through 6: species claims

Claims 4, 5, and 6 are compound-specific method claims. A defendant could avoid literal infringement of one species claim by using a different compound, but that compound could remain within claim 1 or claim 3 if it satisfies the broader structural limitations.

Claim 7: dose limitation

Claim 7 requires administration of 2 to 17 mg/kg per day.

This is a substantial limitation. A method using a dose below 2 mg/kg/day or above 17 mg/kg/day would not literally satisfy claim 7, although it could still fall within claim 1, which contains no numerical dose range.

The stated dose range corresponds approximately to:

Patient body weight	2 mg/kg/day	17 mg/kg/day
50 kg	100 mg/day	850 mg/day
60 kg	120 mg/day	1,020 mg/day
70 kg	140 mg/day	1,190 mg/day
80 kg	160 mg/day	1,360 mg/day

Claim 8: adult dose limitation

The supplied text states that claim 8 depends on claim 18. No claim 18 appears in the provided claim set. If the issued patent actually contains this dependency, claim 8 has a facial dependency problem. If "claim 18" is an OCR or transcription error for claim 1 or claim 7, the legal scope would differ materially.

The stated dosage is approximately 150 to 1,200 mg/day for an adult of normal weight. If claim 8 depends on claim 7, it would likely require both the weight-based range and the adult daily-dose limitation. If it depends on claim 1, it would require the broad method elements plus the adult dose.

The patent’s issued claims and prosecution history control. A claim-dependency error should be checked against the certified patent document before being used in litigation, licensing, or freedom-to-operate work.

What therapeutic uses are covered?

The patent’s core therapeutic theory is treatment or prevention of impaired memory. The express disease list in claim 2 includes Alzheimer’s dementia and other dementia syndromes.

The claims do not require:

A particular severity of dementia.
A particular treatment duration.
A specific dosing frequency.
A specific pharmaceutical excipient.
A particular route other than oral or rectal administration.
A diagnostic test before administration.
Monotherapy rather than combination therapy.
A particular clinical endpoint, such as improvement in recall, attention, or cognitive score.

The absence of a treatment-duration limitation broadens claim 1. Conversely, the requirement that the patient have an impaired memory condition restricts the claim. Administration of carbamazepine for epilepsy, trigeminal neuralgia, or bipolar disorder would not ordinarily satisfy the memory-condition limitation merely because the patient also receives the drug.

What formulations are protected by U.S. Patent 4,409,212?

The patent does not claim a formulation as such.

It covers the use of the specified active compounds when administered orally or rectally. The claim does not identify:

Tablets.
Capsules.
Suspensions.
Suppositories.
Controlled-release systems.
Enteric coatings.
Particular excipients.
Particle sizes.
Salt forms.
Polymorphs.
Dissolution profiles.
Manufacturing parameters.

A tablet, capsule, oral suspension, or rectal dosage form could be relevant to the method claims if it delivers a claimed active compound to a human for the claimed purpose. The formulation itself would not be protected by this patent independently of the claimed therapeutic use.

Separate patents historically covered commercial dosage forms, extended-release products, crystalline forms, process improvements, or specific prodrugs. Those patents must be analyzed separately from U.S. Patent 4,409,212.

When did U.S. Patent 4,409,212 lose exclusivity?

U.S. Patent 4,409,212 issued on October 11, 1983. For a patent governed by the pre-Uruguay Round patent-term rule, the ordinary term was 17 years from grant. On that basis, the patent expired on October 11, 2000, subject to any terminal disclaimer, disclaimer, or unusual term adjustment shown in the official patent record.[1][2]

Event	Date or status
U.S. patent issued	October 11, 1983
Ordinary pre-1995 patent term	17 years from issue
Expected ordinary expiration	October 11, 2000
Current enforceability	Expired
Current patent-based barrier to generic entry	None from this patent

The patent is therefore relevant as historical prior art and as a source of claim interpretation, but not as a live blocking patent in the United States.

Patent expiration does not erase the historical patent rights during the term. It means that the patentee can no longer obtain injunctive relief or damages for post-expiration conduct based on the patent.

What is the Orange Book status of carbamazepine and oxcarbazepine?

U.S. Patent 4,409,212 is not a current Orange Book barrier for carbamazepine or oxcarbazepine.

The FDA Orange Book lists approved drug products and, where applicable, patents and regulatory exclusivities submitted by NDA sponsors. A patent directed to a dementia method would also face listing constraints if the approved labeling did not include that use. FDA patent listing is tied to statutory listing requirements and the approved NDA product, not to every patent that historically mentions an active ingredient.[3]

Carbamazepine

Carbamazepine has long been available in multiple generic dosage forms. Its major approved uses include seizure disorders and trigeminal neuralgia. The patent at issue does not protect those uses. It also does not prevent generic manufacturers from marketing carbamazepine for approved non-dementia indications.

Oxcarbazepine

Oxcarbazepine was commercialized as Trileptal and is available in generic immediate-release tablets and oral suspension. Its approved use is primarily seizure treatment, not Alzheimer’s dementia or general memory impairment.[4]

The historical dementia-use patent could have been relevant to a labeled or promoted dementia indication during its term. It is no longer an Orange Book-based obstacle to generic oxcarbazepine.

Which companies challenged the patent through Paragraph IV litigation?

No current Paragraph IV challenge is commercially relevant to U.S. Patent 4,409,212 because the patent expired in 2000.

A Paragraph IV certification applies when an ANDA applicant asserts that a listed patent is invalid, unenforceable, or not infringed. It is a Hatch-Waxman mechanism associated with listed patents that remain capable of delaying approval. An expired patent cannot create the usual 30-month stay against FDA approval.[5]

The patent’s age also makes modern Paragraph IV litigation unlikely. Any historical ANDA dispute would need to be located in FDA records, court dockets, or the Orange Book archival materials. The patent number itself does not establish that a Paragraph IV case occurred.

What patent litigation affects this patent?

The supplied claim set identifies a patent-expired method-of-use estate. No active enforcement position arises from U.S. Patent 4,409,212.

The principal litigation issues that would have mattered during the patent term were:

Whether a defendant administered a claimed dibenzazepine compound.
Whether the patient had an impaired memory condition.
Whether the administration was oral or rectal.
Whether the amount was prophylactically or therapeutically effective.
Whether the accused compound fit the structural Markush definition.
Whether the patent was enabled across the full claimed genus.
Whether the specification provided adequate written description for the dementia indications and compound classes.
Whether the claims were anticipated or rendered obvious by prior anticonvulsant and neuropharmacology disclosures.

The "effective amount" limitation could have generated factual disputes over clinical efficacy and dose. The broad claim to impaired memory would also have created potential enablement and written-description issues, particularly if the specification contained limited human evidence across multiple dementia types.

Those issues have no current injunctive significance because the patent has expired.

How strong was the patent estate?

Strength during the patent term

The patent had several characteristics that would have increased enforcement reach:

A broad independent method claim.
Coverage of multiple related compounds.
Explicit coverage of oral and rectal administration.
Disease-specific dependent claims.
Dose-specific fallback claims.
Species claims for carbamazepine and oxcarbazepine.

The estate was weaker on product exclusivity because it did not claim the active compounds themselves. Carbamazepine and related dibenzazepines were known chemical entities or closely related to known compounds. Competitors could potentially design around the patent by:

Using a different active ingredient.
Treating a non-memory indication.
Using a different route.
Avoiding the claimed dose where the narrower dose claims were asserted.
Challenging the breadth, enablement, or validity of the method claims.

Current strength

The current enforceability strength is zero because the patent expired. Its residual business value is limited to:

Historical freedom-to-operate analysis.
Prior-art assessment.
Prosecution-history review.
Patent-family mapping.
Understanding the origin of dementia-use claims for dibenzazepines.

Does the patent create biosimilar risk?

No. Carbamazepine and oxcarbazepine are chemically synthesized small molecules, not biologics. Biosimilar provisions under the Public Health Service Act do not apply.

The relevant competitive pathways are:

ANDA generic approval under section 505(j) of the Federal Food, Drug, and Cosmetic Act.
NDA approval for a new indication or reformulation.
Potential 505(b)(2) approval for a modified active ingredient, prodrug, route, or formulation.

The patent does not block any of these pathways today.

What manufacturing and intellectual-property barriers remain?

U.S. Patent 4,409,212 does not claim manufacturing.

Potential barriers must be separated by molecule:

Product	Potential non-212 IP issues
Carbamazepine	Crystalline form, formulation, dissolution, manufacturing-process, and combination-product patents
Oxcarbazepine	Suspension, extended-release, formulation, process, and product-specific patents
Eslicarbazepine acetate	Prodrug composition, stereochemistry, formulation, method-of-use, and manufacturing patents
10-hydroxy carbamazepine	Stereochemical, salt, formulation, and process rights

Expired compound-use claims do not eliminate later patent rights covering a different formulation, stereoisomer, prodrug, delivery system, or manufacturing process. A generic applicant must conduct a current patent search against the target product and proposed labeling.

How does this patent compare with later carbamazepine and oxcarbazepine patents?

Issue	U.S. Patent 4,409,212	Later product patents
Claim type	Method of treating impaired memory	Often formulation, prodrug, process, or approved-use claims
Principal compounds	Carbamazepine, oxcarbazepine, 10-hydroxy derivative	Product-specific compounds or dosage forms
Route	Oral or rectal	Often route and dosage-form specific
Indication	Dementia and impaired memory	Commonly epilepsy or other labeled indications
Term status	Expired in 2000	Must be reviewed individually
Orange Book relevance	No current blocking effect	Potentially relevant if properly listed
Generic impact	No current barrier	Depends on patent term and ANDA certifications

The 212 patent should not be treated as a substitute for an Orange Book and non-Orange Book landscape search. Small-molecule products may face later patents that are not captured by the original compound-use patent.

Key Takeaways

U.S. Patent 4,409,212 is a method-of-treatment patent for impaired memory conditions.
Claim 1 broadly covers oral or rectal administration of defined dibenzazepine carboxamides.
Claim 2 specifically identifies senile dementia, multi-infarction dementia, and Alzheimer’s dementia.
Claim 4 covers carbamazepine.
Claim 5 covers oxcarbazepine.
Claim 6 covers 10-hydroxy carbamazepine or a related licarbazepine compound.
Claims 7 and 8 impose dose restrictions, but the supplied text contains a likely dependency error in claim 8.
The patent issued October 11, 1983, and its ordinary term expired October 11, 2000.
It has no current U.S. exclusivity or Paragraph IV significance.
It is not a formulation, manufacturing, biologic, or biosimilar patent.
Current launch risk depends on later patents covering formulations, prodrugs, stereoisomers, processes, and approved labeling.

FAQs About U.S. Patent 4,409,212

Does U.S. Patent 4,409,212 still prevent use of carbamazepine for Alzheimer’s disease?

No. The patent expired in 2000 and cannot currently block that use on a patent-infringement theory.

Is oxcarbazepine protected by an active U.S. patent from this patent family?

Not by U.S. Patent 4,409,212. Any active protection would have to arise from later patents covering oxcarbazepine formulations, manufacturing, or other product-specific features.

Is claim 6 directed to eslicarbazepine acetate?

Not on the face of the supplied language. Claim 6 recites a 10-hydroxy dibenzazepine carboxamide, while eslicarbazepine acetate is an acetate ester prodrug.

Can a generic manufacturer rely on the expiration of this patent for an ANDA?

Yes, as to this patent. The applicant must still address any later-listed patents and regulatory exclusivities associated with the target reference-listed drug.

Does the patent cover treatment of epilepsy with carbamazepine?

No, not under the supplied claims. The claims require prevention or treatment of an impaired memory condition. Epilepsy treatment is outside that express disease limitation unless the accused method also satisfies the memory-condition requirement.

References

United States Patent and Trademark Office. (1983). United States Patent No. 4,409,212.
35 U.S.C. § 154. Patent term provisions applicable to patents issued under the pre-Uruguay Round framework.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
U.S. Food and Drug Administration. (2023). Trileptal (oxcarbazepine) prescribing information.
U.S. Food and Drug Administration. (2024). ANDA submissions: Content and format of an abbreviated new drug application.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Switzerland	2565/81	Apr 16, 1981

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	8263382	⤷ Start Trial
Belgium	892882	⤷ Start Trial
Switzerland	649080	⤷ Start Trial
Italy	1147841	⤷ Start Trial
Italy	8248224	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,409,212

Summary for Patent: 4,409,212