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Details for Patent: 4,534,973
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Summary for Patent: 4,534,973
| Title: | Pharmaceutical compositions | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Abstract: | Compositions for the relief of pain, muscle spasm and limited mobility associated with acute painful muscoloskeletal conditions are disclosed. Such compositions comprise in combination, a N-monosubstituted-2, 2-dialkyl-1, 3-propanediol dicarbamate and aspirin. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Inventor(s): | Miwon S. Kim | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assignee: | Meda Pharmaceuticals Inc | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Application Number: | US06/635,962 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Patent Claim Types: see list of patent claims | Use; Composition; Dosage form; | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Patent landscape, scope, and claims: | # United States Patent 4,534,973: Claim Scope, Expiration, FDA Status, and Carisoprodol-Aspirin Patent Landscape U.S. Patent No. 4,534,973 covers an oral therapeutic combination of aspirin and carisoprodol, chemically identified in the patent as N-propyl-2-methyl-2-propyl-1,3-propanediol dicarbamate. Its principal commercial concept is the 2:1 aspirin-to-carisoprodol combination historically marketed as Soma Compound. The patent claims a composition and a treatment method, not carisoprodol itself. The patent issued on August 13, 1985. Under the pre-1995 patent-term rules applicable to the patent, its ordinary 17-year term ran from issuance and ended in August 2002, absent an unusual term adjustment or enforceability event. The patent therefore does not present a current U.S. blocking right against generic carisoprodol, aspirin, or their combination. [1][2] What drug and formulation does U.S. Patent 4,534,973 protect?The claimed muscle relaxant is carisoprodol. The patent uses the older chemical designation:
The commercial product associated with this combination is commonly identified as Soma Compound. Current labeling for the product describes a combination of carisoprodol and aspirin for the relief of discomfort associated with acute, painful musculoskeletal conditions. [3] The patent is narrow in its active-ingredient combination. It does not broadly claim:
Its core technical limitation is the combination of aspirin and carisoprodol in a specified weight ratio. What are the claims of U.S. Patent 4,534,973?The patent has four claims, divided between composition claims and method-of-treatment claims.
Claims 2 and 4 are dependent claims. They do not create independent subject matter outside the scope of claims 1 and 3. Their practical purpose is to focus protection on the preferred 2:1 formulation. How broad is claim 1?Claim 1 combines several limitations that must be present for infringement. A covered product must have:
The word “comprising” makes claim 1 open-ended. A product can contain additional ingredients, including excipients, binders, coatings, colorants, stabilizers, or other components, while potentially remaining within the claim. The presence of additional active ingredients would require a separate analysis, but the claim does not on its face exclude them. The ratio limitation is central. A formulation with 325 mg of aspirin and 200 mg of carisoprodol has a 1.625:1 weight ratio and falls within the claimed numerical range if the other limitations are satisfied. A 325 mg aspirin/350 mg carisoprodol product has a ratio of approximately 0.93:1 and is outside the literal 1:1-to-2:1 range. The phrase “about” introduces ordinary measurement tolerance. It does not eliminate the importance of the ratio. A materially different ratio would create a stronger noninfringement position, although the doctrine of equivalents could become relevant in an infringement dispute. What does claim 2 add to the patent scope?Claim 2 limits claim 1 to a composition containing two parts aspirin per part carisoprodol. This is a formulation-specific claim. It is narrower than claim 1 because a product must satisfy the more precise 2:1 ratio. The claim also retains the unit-dose and therapeutic-use limitations from claim 1. A standard product containing 325 mg of aspirin and 200 mg of carisoprodol has a 1.625:1 ratio and would not literally satisfy a 2:1 claim. A product containing 325 mg of aspirin and approximately 162.5 mg of carisoprodol would more closely match a 2:1 ratio, subject to the patent’s “about” language and applicable claim construction. How do claims 3 and 4 differ from claims 1 and 2?Claims 3 and 4 are method claims. They require oral administration to a warm-blooded animal in need of treatment. The method claims add three meaningful limitations:
Claims 3 and 4 use “consisting essentially of.” That transition is narrower than “comprising.” It generally permits inactive ingredients and components that do not materially affect the basic and novel characteristics of the claimed combination. An additional ingredient that materially changes the pharmacological function, dosage relationship, or therapeutic character could create a stronger argument that the formulation falls outside the claim. Claim 3 also says “therapeutic amount.” That limitation ties the method to administration sufficient to produce the claimed treatment effect. A composition containing the ingredients but not administered therapeutically would not necessarily satisfy the method claim. The wording “warm-blooded animals” is broad from a species perspective, but the claim still requires oral treatment for the specified acute painful musculoskeletal conditions. Veterinary use could fall within the literal language if the other limitations are met. What formulations are protected by U.S. Patent 4,534,973?The patent principally covers immediate-release oral unit doses containing aspirin and carisoprodol within the claimed ratio range.
The claims do not expressly require a particular tablet weight, excipient system, dissolution profile, coating, manufacturing process, or release mechanism. Those features may affect infringement or validity analysis, but they are not explicit claim limitations. When did U.S. Patent 4,534,973 expire?U.S. Patent 4,534,973 issued August 13, 1985. For a U.S. patent subject to the pre-June 8, 1995 term regime, the ordinary term was 17 years from issuance. On that basis, the patent expired on August 13, 2002. [1][2] The expiration has several consequences:
Patent expiration does not eliminate historical relevance. The patent may remain relevant to prior-art analysis, prosecution history, freedom-to-operate diligence concerning historical conduct, and assessment of why the original combination product was commercially differentiated. What is the FDA and Orange Book status of the combination?Carisoprodol is an FDA-approved prescription skeletal muscle relaxant. Combination products containing carisoprodol and aspirin have been marketed for acute musculoskeletal pain and muscle spasm. The product labeling identifies the combination as a short-term treatment, consistent with the clinical positioning of Soma Compound. [3] The Orange Book distinguishes between active and discontinued products and between patents that are currently listed and patents that have expired. A patent that expired in 2002 cannot provide current Orange Book exclusivity. Any historical listing of U.S. Patent 4,534,973 would have no present blocking effect. The combination is a small-molecule drug product, not a biologic. Biosimilar procedures under the Biologics Price Competition and Innovation Act do not apply. A competing product would generally proceed through an abbreviated new drug application, a suitability pathway where available, or a full new drug application, depending on the reference-product and formulation circumstances. [4] Are there current Paragraph IV challenges to this patent?No current Paragraph IV challenge can create commercial risk under U.S. Patent 4,534,973 because the patent expired in 2002. Paragraph IV certifications apply to unexpired patents listed in the Orange Book. A generic applicant may certify that a listed patent is invalid, unenforceable, or will not be infringed. Once a patent has expired, it no longer supports a Paragraph IV challenge or a 30-month stay based on that patent. [4] Any historical ANDA litigation involving a carisoprodol-aspirin product would need to be evaluated separately from the current status of Patent 4,534,973. The expired patent itself is not a present litigation obstacle. What patent litigation and settlement agreements affect the combination?Patent 4,534,973 does not create an active U.S. litigation issue after its 2002 expiration. No current settlement agreement can extend the patent’s statutory term or restore enforcement rights. A diligence review should distinguish among:
A trademark settlement or product-liability resolution would not revive an expired composition or method patent. Likewise, a later patent on a formulation, dosage regimen, manufacturing process, or abuse-deterrent system would require separate claim analysis and would not inherit the scope of Patent 4,534,973. How strong is the patent estate for aspirin and carisoprodol?The estate is weak as a current exclusivity position because the principal combination patent is expired and the underlying active ingredients are longstanding small molecules.
The strongest potential barriers for a new entrant would come from a later, unexpired patent claiming a specific formulation, dosage regimen, manufacturing process, or delivery system. Patent 4,534,973 does not cover those categories unless they also satisfy its express limitations. How does the patent compare with modern generic-entry risks?For a conventional immediate-release oral aspirin-carisoprodol product, regulatory and commercial execution are more important than Patent 4,534,973. Key entry issues include:
Carisoprodol is a Schedule IV controlled substance under the federal Controlled Substances Act. That status creates compliance and supply-chain obligations but does not create patent exclusivity. [5] What geographic coverage does the patent provide?U.S. Patent 4,534,973 provides U.S. rights only. It cannot directly block manufacture, sale, use, or importation outside the United States. Foreign protection would depend on separate national or regional patent applications. A U.S. patent number does not establish active rights in Canada, Europe, Japan, or other jurisdictions. Any international family member would require independent review of:
Because the U.S. patent expired in 2002, any foreign family member would also be expected to face substantial age-related expiration risk, although foreign term rules can differ. Key Takeaways
FAQs About U.S. Patent 4,534,973Does U.S. Patent 4,534,973 cover Soma Compound?Yes. The claim structure corresponds to the aspirin-carisoprodol combination historically marketed as Soma Compound, subject to the claimed dosage form, therapeutic-use, and ratio limitations. Can a company sell carisoprodol without licensing this patent?Yes. Patent 4,534,973 expired in 2002. It does not require a current license for carisoprodol or for an aspirin-carisoprodol product. Is a 325 mg aspirin and 200 mg carisoprodol tablet within the claimed ratio?Its ratio is 1.625:1 by weight, which is within the approximately 1:1 to 2:1 range in claims 1 and 3, assuming the remaining claim limitations are satisfied. It is not the exact 2:1 ratio recited by claims 2 and 4. Does the patent cover a carisoprodol extended-release formulation?Not automatically. An extended-release formulation would need to satisfy every applicable limitation, including the aspirin ingredient, unit-dose requirement, ratio range, and therapeutic-purpose limitations. A separate later patent could also apply. Is carisoprodol subject to biosimilar competition?No. Carisoprodol is a small-molecule drug. Competition generally proceeds through generic-drug pathways rather than the biosimilar framework. References
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Drugs Protected by US Patent 4,534,973
| Applicant | Tradename | Generic Name | Dosage | NDA | Approval Date | TE | Type | RLD | RS | Patent No. | Patent Expiration | Product | Substance | Delist Req. | Patented / Exclusive Use | Submissiondate |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| >Applicant | >Tradename | >Generic Name | >Dosage | >NDA | >Approval Date | >TE | >Type | >RLD | >RS | >Patent No. | >Patent Expiration | >Product | >Substance | >Delist Req. | >Patented / Exclusive Use | >Submissiondate |
