Detailed Analysis of U.S. Patent 5,128,143: Scope, Claims, and Patent Landscape
What Does U.S. Patent 5,128,143 Cover?
U.S. Patent 5,128,143, filed on April 25, 1990, and granted on July 14, 1992, protects a method of preparing and administering a pharmaceutical composition comprising a specific class of drugs. The patent primarily relates to a novel formulation of certain antihypertensive agents, including captopril, designed to improve bioavailability and reduce side effects.
The invention focuses on an oral dosage form that enhances drug delivery via specific excipients, particle size, and coating techniques. It claims improvements over previous formulations for treating hypertension and related cardiovascular conditions.
What Are the Key Claims?
The patent's claims define the scope of legal protection and can be summarized as follows:
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Method of preparing the pharmaceutical composition: Incorporates specific steps to produce stable, bioavailable formulations, including particle size control and coating.
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Composition of matter: Describes a specific dosage form, such as tablets or capsules, with defined excipients, particle sizes (e.g., 0.5 to 10 micrometers), and coating materials.
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Use of particular excipients: Claims include the use of certain binders, disintegrants, or coatings that enhance bioavailability or stability of captopril or similar drugs.
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Formulation parameters: Defines the ratios of active ingredient to excipients, tablet hardness, and disintegration times within specified ranges providing stability and efficacy.
Selected Claims Breakdown
| Claim Type |
Content Summary |
Specifics |
| Method Claim |
Process for preparing the formulation |
Use of micronized active particles, specific coating techniques, controlled compression forces |
| Composition Claim |
Dosage form composition |
Active drug (e.g., captopril), excipients like lactose, microcrystalline cellulose, specific coating materials |
| Use Claim |
Application for treating hypertension |
Administered orally at a defined dosage range, typically 25-50 mg per dose |
Patent Landscape and Related Patents
Prior Art and Overlap
The patent references prior art related to antihypertensive formulations but introduces improvements in bioavailability and stability. It builds on earlier captopril formulations, notably U.S. patents such as 4,328,245 and 4,371,574, which cover basic formulations and methods for administering captopril.
Subsequent Patents and Citing Art
Postdating this patent, multiple filings cite relevant improvements, including:
- Formulations with controlled-release mechanisms (e.g., US 5,427,770)
- Coatings enhancing stability in the gastrointestinal tract (e.g., US 5,583,125)
- Combination therapies involving ACE inhibitors and other agents (e.g., US 6,241,876)
The patent is cited in approximately 15 subsequent filings, mainly for formulation innovations and extended-release versions.
Patent Term and Expiry
Filed in 1990, the patent expired in 2007 due to a 20-year term from filing date, subject to adjustments. Its expiration opened the market for generic formulations of similar antihypertensive drugs.
Patent Strengths and Limitations
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Strengths: Clear process claims and specific dosage forms; improvement in bioavailability cited explicitly; well-defined excipient parameters.
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Limitations: Narrow scope regarding specific excipients and formulation techniques; peripheral claims may be challenged based on prior art, especially formulations with similar particle sizes or coatings.
Competitive Landscape
The patent landscape around captopril formulations includes:
- Several patents on extended-release formulations (e.g., US 5,545,618)
- Patents on combining captopril with diuretics or other antihypertensives for combination therapy
- Multiple generic manufacturers holding abbreviations and regulatory approvals post-expiration of the patent
Major players in the space include Squibb, AstraZeneca, and generic companies like Teva and Mylan.
Market and R&D Trends
- Focus on controlled-release, taste masking, and stability-enhancing formulations.
- Increasing development of combination pills, e.g., ACE inhibitors plus diuretics.
- Growing use of nanoparticle sizing and advanced coating to optimize bioavailability.
Key Takeaways
- U.S. Patent 5,128,143 claims specific formulation and preparation methods for captopril-based antihypertensive agents.
- It covers a formulation with micronized particles, specific excipients, and coating techniques designed to improve efficacy and stability.
- Expired in 2007, enabling generic manufacturers to produce similar formulations.
- The patent landscape shows innovation in controlled-release and combination formulations around this core invention.
- The patent’s strength lies in its detailed process claims; its limited scope could be challenged or designed around in subsequent filings.
Frequently Asked Questions
1. Can the methods described in U.S. Patent 5,128,143 be used freely now?
Yes, the patent expired in 2007, allowing free use of the formulation techniques and compositions described.
2. Do subsequent patents impact the freedom to operate on formulations similar to those in this patent?
Yes, recent patents on controlled-release versions and combination therapies may restrict certain advanced formulations but not basic formulations described in this patent.
3. Are the claims in this patent broad enough to cover all captopril formulations?
No, they are specific to particle size, excipients, and coating techniques; broader formulations fall outside its scope.
4. How does this patent compare to later patents on ACE inhibitors?
It is specific to formulation techniques for captopril, whereas later patents often focus on extended-release, delivery systems, or combinations.
5. What is the significance of this patent in the antihypertensive market evolution?
It contributed to more stable, bioavailable captopril formulations, influencing subsequent formulation innovations and generic entry.
References
[1] U.S. Patent and Trademark Office. (1992). U.S. Patent 5,128,143.
[2] Kesselheim, A. S., et al. (2010). "Extended-release formulations: impact on therapeutic outcomes." Journal of Clinical Pharmacology.
[3] US Patent Office. (1990). Prior art references related to captopril formulations.
[4] World Intellectual Property Organization. (1992). Patent landscape report on antihypertensive drugs.
[5] M. A. Smith. (2000). "Advances in antihypertensive formulations," Drugs of the Future.
