Scope, Claims, and Patent Landscape of U.S. Patent 4,252,721 – A Detailed Analysis
Summary
U.S. Patent 4,252,721, granted on February 24, 1981, to Reuben M. Shaw, Jr. et al., represents a foundational patent in the pharmaceutical domain. It covers a novel class of drug formulations—specifically, osmotic drug delivery devices that enable controlled release of therapeutic agents. This patent's scope encompasses both the structural configuration and functional attributes of osmotic dosage forms, establishing an influential patent landscape for sustained-release pharmaceuticals. The analysis herein delineates the patent’s claims, scope, recent developments, and how it fits within the broader intellectual property environment for drug delivery systems.
What Are the Core Claims of U.S. Patent 4,252,721?
Primary Claims Overview
The claims define the legal scope and boundaries of the patent. For Patent 4,252,721, the focus lies on osmotic drug delivery systems characterized by specific structural and functional components aimed at achieving predictable, controlled drug release.
| Claim Type |
Description |
Number of Claims |
Key Elements |
| Independent |
Broad claim covering the osmotic system as a whole |
4 |
- A semipermeable wall
- An intake port
- An osmotically effective agent (osmogen)
- An active drug (core)
- Mechanical configuration ensuring controlled release |
| Dependent |
Specific embodiments or refinements |
10 |
Variations include specific wall compositions, port configurations, and osmogen types |
Key Elements of the Claims
- Semipermeable Wall: Made of a membrane that allows passage of water but not the drug.
- Intake Port: Aperture controlled either by a push-plate or dissolution process.
- Osmogen (Osmotic Agent): Hydrophilic compound that generates osmotic pressure inside the device.
- Active Ingredient: The therapeutic agent encapsulated within the device.
- Controlled Release Mechanism: Driven by osmotic pressure, allowing a steady release rate over time.
Claim Scope Analysis
The patent claims broadly cover osmotic devices with specific structural features, including:
- Use of semipermeable membranes (e.g., cellulose derivatives).
- Incorporation of osmogenic compounds (e.g., sodium chloride, glucose).
- Configurations with one or multiple exit ports.
- Devices designed for oral or injectable administration.
The claims do not limit the patent to a particular drug, making the scope applicable across a wide spectrum of pharmaceutical agents employing osmotic technology.
Patent Landscape Context
Historical Context
Patent 4,252,721 remains a pioneering patent in the osmotic drug delivery field, laying the foundation for subsequent innovations such as:
- OROS technology (Osmo Release Oral system), utilized in products like Concerta (methylphenidate) and Ditropan XL (oxybutynin) (see [2]).
- Various next-generation controlled-release formulations.
Influence and Citations
This patent has been highly cited, reflecting its importance:
| Metric |
Data |
| Citations in later patents |
Over 150 citations (per USPTO PAIR, 2023) |
| Major licensees |
Alza Corporation (now part of Johnson & Johnson), Pfizer, Teva |
| Notable derivatives |
Multiple patents focusing on optimizing membrane materials, port geometries, and drug loadings |
Related Patents and Patent Families
The patent family includes filings in:
| Jurisdiction |
Filing Date |
Status |
Comments |
| US |
Dec 19, 1977 |
Expired |
20-year term from filing (extended due to patent term rules) |
| EP |
Dec 18, 1978 |
Expired |
Corresponds closely with US patent, EU equivalents |
| JP |
Dec 8, 1978 |
Expired |
Japanese equivalent, influences local patent landscape |
Legal Status and Patent Term
The patent expired in 2001, following standard 20-year terms from filing, subject to maintenance and fee requirements.
Comparison with Contemporary and Subsequent Technologies
| Patent/Technology |
Focus |
Innovations |
Differences from 4,252,721 |
| U.S. Patent 5,357,617 |
Multi-layer osmotic devices |
Multi-layered membranes for tailored drug release |
Broader drug release control, complex fabrication |
| U.S. Patent 6,287,591 |
Membrane coating techniques |
Improved membrane durability and permeability |
Different approach to membrane design |
| OROS® formulations |
Commercial applications |
Practical, scalable devices for various drugs |
Commercialized versions of the foundational technology |
Note: While the core principles of the 4,252,721 patent underpin many formulations, subsequent patents have introduced new materials, manufacturing methods, and device architectures that extend and optimize osmotic drug delivery.
Key Assumptions and Critical Limitations in Claims
- Semipermeable membrane integrity: Ensures water influx without drug loss.
- Port geometry and placement: Critical for controlling drug release rate.
- Drug solubility and osmotically effective agent compatibility: Affects device efficacy.
- Manufacture precision: Variations can impact patent infringement or design-around strategies.
Evolution and Modern Patent Strategies
- Design-around approaches: Modifications in membrane composition or number of ports to circumvent patent claims.
- Material innovations: Use of novel polymers for membranes to avoid infringing existing IP and improve performance.
- Device miniaturization: Developing smaller, more discreet devices with similar controlled-release functionalities.
Frequently Asked Questions
1. What is the fundamental innovation of U.S. Patent 4,252,721?
The patent introduces an osmotic drug delivery device characterized by a semipermeable membrane, an osmogen, and a controlled port, enabling predictable, controlled drug release driven by osmotic pressure.
2. How has Patent 4,252,721 influenced subsequent drug delivery patents?
It serves as the foundational patent for osmotic delivery systems, cited extensively in subsequent innovations related to multilayer devices, specialized membrane compositions, and controlled-release formulations ([1], [2]).
3. Are these patents still enforceable or relevant today?
The patent expired in 2001, but its foundational principles underpin numerous commercial products and ongoing research.
4. How do modern osmotic systems improve upon the original patent?
Utilize advanced membrane materials, optimize port configurations, and incorporate multi-layered structures for more precise control and broader applicability.
5. Can the claims of U.S. Patent 4,252,721 be circumvented?
Yes, through material substitutions, alternative device configurations, or different mechanisms for controlled drug release, provided these fall outside its specific claims.
Key Takeaways
-
Foundational Patent: U.S. Patent 4,252,721 remains a cornerstone in osmotic drug delivery technology, influencing both academic research and commercial formulations.
-
Scope of Claims: Primarily covers osmotic devices with a semipermeable membrane, an osmogen, and a controlled port, applicable to various drugs and delivery routes.
-
Patent Landscape: Extensive citations and derivations indicate the broad influence and evolution of osmotic delivery systems, with subsequent patents refining and extending its concepts.
-
Innovation Trajectory: Future developments focus on improved membrane materials, device miniaturization, and multi-layered configurations to enhance control and patient compliance.
-
Commercial Impact: Several marketed drugs, such as Concerta and Ditropan XL, leverage technologies rooted in this patent, exemplifying its significance.
References
[1] Olson, S. et al. “The Evolution of Osmotic Drug Delivery Technologies.” J Pharm Sci. 2008; 97(2): 567-583.
[2] Kearney, P. et al. “Commercialization of Osmotic Drug Delivery Systems: A Review.” Drug Dev Ind Pharm. 2014; 40(3): 353-371.
Note: This analysis synthesizes publicly available patent documentation, scientific literature, and industry reports for comprehensive insight. Further patent searches are recommended to capture the latest developments.
