United States Patent 4,585,790: A Detailed Analysis of Scope, Claims, and Patent Landscape
Introduction
The United States Patent 4,585,790, titled "Aqueous Based Ranitidine Formulation," was granted on April 29, 1986, to inventors Padfield et al. and assigned to Baxter International Inc. This patent is significant in the pharmaceutical industry, particularly in the formulation and stability of ranitidine, a widely used medication for treating ulcers and gastroesophageal reflux disease (GERD).
Background of Ranitidine
Ranitidine, a histamine H2-receptor antagonist, was first introduced in the 1980s and quickly became a popular treatment for various gastrointestinal disorders. However, its stability in aqueous solutions was a significant challenge due to its tendency to degrade rapidly, especially at lower pH levels[1].
Scope of the Patent
The patent 4,585,790 addresses the stability issue of ranitidine in aqueous solutions by introducing a buffered formulation. Here are the key aspects of the patent's scope:
Buffered Formulation
The patent describes an aqueous based ranitidine formulation that is buffered to maintain a pH range of 6.5 to 7.5. This buffering is achieved using citrate and phosphate salts, which significantly enhance the stability of ranitidine compared to unbuffered solutions[1].
Stability Enhancement
The buffered formulation reduces the rate of degradation of ranitidine. For instance, the patent notes that the rate of breakdown in ranitidine is about 10 times faster for a solution buffered to a pH of 5.5 than for a solution buffered to pH 7.0. This stability enhancement is crucial for maintaining the potency of the medication over its shelf life[1].
Claims of the Patent
The patent includes several claims that define the scope of the invention:
Claim 1: Buffered Aqueous Solution
The first claim describes an aqueous solution of ranitidine hydrochloride buffered to a pH range of 6.5 to 7.5 using citrate and phosphate salts[1].
Claim 2: Concentration of Ranitidine
Subsequent claims specify the concentration of ranitidine hydrochloride in the solution, typically ranging from about 0.1 to 10 mg/mL[1].
Claim 3: Buffering Agents
Claims also detail the use of specific buffering agents, such as citric acid and sodium citrate, or phosphoric acid and sodium phosphate, to maintain the desired pH range[1].
Patent Landscape
The patent landscape surrounding US 4,585,790 is complex and involves several related patents and publications.
Prior Art
The patent cites several prior art documents, including U.S. patents such as 4,021,481 and 4,128,658, which also deal with pharmaceutical formulations but do not address the specific stability issues of ranitidine in aqueous solutions[1].
Related Patents
Other patents, such as U.S. Patent 5,169,864, discuss unbuffered premixed ranitidine formulations and their stability issues, highlighting the innovation of the buffered formulation in US 4,585,790[1].
Industry Impact
The buffered ranitidine formulation patented in US 4,585,790 has had a significant impact on the pharmaceutical industry. It has enabled the widespread use of ranitidine in various medical settings by ensuring the stability and potency of the medication over time.
Legal and Inventorship Aspects
Determining the true and only inventors is crucial in patent law. The USPTO requires that patent applications list the correct inventors to ensure the patent's enforceability[2].
Inventorship
In the case of US 4,585,790, the inventors listed are Padfield et al., and the patent is assigned to Baxter International Inc. Ensuring that the inventors are correctly identified is essential for maintaining the patent's validity and enforceability[1].
Data and Statistics
The stability of ranitidine in buffered solutions has been extensively studied. For example, a study by Galante et al. published in the American Journal of Hospital Pharmacy discusses the short-term stability of ranitidine hydrochloride at dilute concentrations in intravenous infusion fluids at room temperature[1].
Global Patent System
The global patent system, facilitated by services like the Global Dossier and Common Citation Document (CCD), helps in managing and searching patent families across different IP offices. This harmonization is crucial for ensuring that similar inventions are treated consistently worldwide[4].
Conclusion
The United States Patent 4,585,790 represents a significant advancement in the formulation of ranitidine, ensuring its stability and efficacy in aqueous solutions. The buffered formulation described in the patent has had a lasting impact on the pharmaceutical industry, enabling the widespread use of ranitidine.
Key Takeaways
- Buffered Formulation: The patent introduces a buffered aqueous ranitidine formulation to enhance stability.
- Stability Enhancement: The buffering agents maintain a pH range of 6.5 to 7.5, significantly reducing the degradation rate of ranitidine.
- Claims: The patent includes specific claims regarding the concentration of ranitidine and the use of buffering agents.
- Patent Landscape: The patent is part of a broader landscape involving related patents and publications on pharmaceutical formulations.
- Legal and Inventorship: Correct identification of inventors is crucial for the patent's enforceability.
FAQs
Q: What is the main innovation of US Patent 4,585,790?
A: The main innovation is the introduction of a buffered aqueous ranitidine formulation to enhance the stability of ranitidine.
Q: Why is buffering important for ranitidine?
A: Buffering maintains a pH range that significantly reduces the degradation rate of ranitidine, ensuring its potency over time.
Q: Who are the inventors listed on US Patent 4,585,790?
A: The inventors listed are Padfield et al.
Q: What are the implications of incorrect inventorship in patent law?
A: Incorrect inventorship can lead to challenges in the enforceability of the patent.
Q: How does the Global Dossier facilitate patent management?
A: The Global Dossier provides a single portal to access file histories of related applications from participating IP offices, enhancing the management and search of patent families globally.
Sources
- US Patent 4,585,790: "Aqueous Based Ranitidine Formulation," Padfield et al., April 29, 1986.
- Determining Inventorship for US Patent Applications: US patent law and inventorship guidelines.
- Patent Claims Research Dataset: USPTO dataset on patent claims and scope.
- USPTO Search and Global Dossier: USPTO services for patent search and global patent management.
