Injectable Paracetamol Formulation Stabilization
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Solution Overview
Problem
The development of stable injectable paracetamol solutions for intravenous use is hindered by paracetamol's instability in aqueous media, particularly due to chemical oxidation and deacetylation, leading to unwanted coloration and impurities, which is exacerbated by storage in certain plastic materials lacking antioxidants.
Innovation Solution
Incorporating substances that can react with the phenolate form of paracetamol, such as reducing sugars, their acid forms, or chemical species with sulfur, to reduce degradation pathways and stabilize the solution, allowing storage in antioxidant-free plastic materials and maintaining colorlessness over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If paracetamol is formulated as an injectable aqueous solution, then it can be administered intravenously for rapid analgesic and antipyretic effects, but it degrades through oxidation and deacetylation causing coloration and impurity formation
Solution Approach 1:
The patent introduces oxygen-scavenging substances (sulfites, bisulfites, thiosulfates, or antioxidants like ascorbic acid and tocopherol) as intermediary agents that react with dissolved oxygen to prevent oxidation of paracetamol. These mediators protect the active ingredient by eliminating the oxidizing environment without directly interacting with paracetamol's therapeutic function.
Solution Approach 2:
The patent adjusts the pH of the aqueous solution to a specific range (pH 3.0-6.0, preferably pH 3.5-5.0) to minimize deacetylation of paracetamol. By controlling this critical parameter, the formulation reduces the formation of p-aminophenol and subsequent degradation products, thereby maintaining solution stability over time.
2Ease of manufacture
If conventional aqueous paracetamol solutions are stored in plastic materials, then storage convenience is improved, but oxidation degradation is accelerated due to oxygen permeability
Solution Approach 1:
The patent employs oxygen-scavenging substances that actively remove dissolved oxygen from the solution, counteracting the oxygen permeability of plastic containers. These intermediaries create an oxygen-depleted environment that prevents oxidation even when stored in conventional plastic materials, eliminating the need for special oxygen-impermeable packaging.
Solution Approach 2:
By incorporating substances that scavenge oxygen and reduce the oxidizing environment, the patent effectively creates an inert atmosphere within the solution. This internal inert environment protects paracetamol from oxidation regardless of the external container material's oxygen permeability characteristics.
3Reliability
If antioxidants are added to prevent paracetamol degradation, then solution stability is improved, but the formulation complexity and cost increase
Solution Approach 1:
The patent optimizes the pH parameter to a range (pH 3.0-6.0) that inherently minimizes deacetylation and oxidation of paracetamol. This parameter adjustment reduces the need for high concentrations of antioxidants, simplifying the formulation while maintaining stability.
Solution Approach 2:
The patent uses small, precise concentrations of oxygen-scavenging substances (e.g., 0.01-0.1% w/v sulfites or 0.05-0.5% w/v antioxidants) targeted specifically at neutralizing dissolved oxygen. This localized approach addresses only the oxidation issue without requiring comprehensive formulation changes, maintaining simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution significantly reduces impurities and color formation, achieving a stable paracetamol solution with minimal impurities that can be stored in various plastic materials, maintaining colorlessness and stability comparable to or exceeding existing formulations, even under heat sterilization and storage conditions.
Implementation Method 1
Incorporating substances that can react with the phenolate form of paracetamol, such as reducing sugars, their acid forms, or chemical species with sulfur, to reduce degradation pathways and stabilize the solution
Implementation Method 2
One of the causes of paracetamol degradation is based on chemical oxidation reactions in which the oxygen present in the solution is the main precursor of this degradation
Implementation Method 3
The secondary cause of degradation may be the deacetylation of the amino group generating p-aminophenol which is also quickly degraded producing p-benzoquinoneimine
Data Source
AI summary
The invention relates to an aqueous paracetamol solution for its use by perfusion with a pH between 4.5 and 6.0, comprising at least one substance that can react with phenolates giving rise to its O-derivatives or other coordination compounds. The injectable paracetamol solution of the present invention has high stability, does not develop color over time and has a minimal content of impurities.