Aprepitant Injectable Formulation Solubility Stability
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Solution Overview
Problem
Aprepitant's poor solubility in water and ethanol limits its bioavailability and stability in pharmaceutical compositions, making it challenging to develop a stable and effective parenteral formulation for injection.
Innovation Solution
A stable liquid formulation of aprepitant is achieved using an aqueous single-phase solvent system comprising water, a primary co-solvent (such as ethanol), a surfactant (like polysorbate 80), and a secondary co-solvent (like dimethylacetamide), with a synergistic ratio to enhance solubilization, allowing concentrations of at least 2 mg/ml and maintaining stability for extended periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If aprepitant is formulated in water or ethanol to achieve solubility, then solubility is improved, but stability deteriorates due to rapid degradation and insufficient storage stability
Solution Approach 1:
The patent introduces a surfactant as an intermediary substance to mediate between aprepitant and the aqueous/ethanolic solvent system. The surfactant forms micelles that solubilize aprepitant while protecting it from degradation, thereby simultaneously improving solubility and maintaining stability.
Solution Approach 2:
The patent creates a composite formulation system combining multiple components (aprepitant, water, ethanol, and surfactant) in specific ratios. This composite approach allows the formulation to achieve both solubility enhancement through the solvent mixture and stability through the protective micellar structure formed by the surfactant.
2Quantity of substance
If fosaprepitant prodrug is used to improve water solubility for parenteral administration, then solubility is improved, but manufacturing complexity and cost increase due to additional synthesis steps
Solution Approach 1:
The patent extracts the solubility-enhancing function from the complex fosaprepitant prodrug molecule and implements it separately through a surfactant-based formulation system. This allows aprepitant itself to be used in parenteral formulations without requiring chemical modification, thereby eliminating the complex phosphorylation and salt formation steps.
Solution Approach 2:
The patent changes the physical-chemical parameters of the formulation system by introducing surfactants and optimizing the water-ethanol ratio, rather than changing the chemical structure of aprepitant itself. This parameter-based approach achieves solubility improvement through formulation science rather than chemical synthesis.
3Quantity of substance
If high ethanol concentration is used to achieve pharmaceutically relevant aprepitant concentrations, then solubility is improved, but toxicity and acceptability worsen
Solution Approach 1:
The surfactant acts as a mediator that enables aprepitant solubilization at low ethanol concentrations. By forming micellar structures, the surfactant provides an alternative solubilization mechanism that reduces dependence on high ethanol concentrations, thereby lowering toxicity while maintaining pharmaceutically relevant aprepitant concentrations.
Solution Approach 2:
The patent optimizes the formulation parameters by reducing ethanol concentration to below 10% v/v and adjusting the water-to-surfactant ratio. These parameter changes achieve the desired aprepitant solubility through the synergistic effect of the aqueous-surfactant system rather than relying on high ethanol content.
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 formulation provides high solubility and stability of aprepitant, enabling effective parenteral administration with prolonged storage stability and bioavailability, overcoming the limitations of existing formulations.
Implementation Method 1
a surfactant and a secondary co-solvent, wherein the primary co-solvent and the surfactant are present in a synergistic ratio with respect to the solubilization of aprepitant
Implementation Method 2
an aqueous single phase solvent system that comprises water, a primary co-solvent... wherein the primary co-solvent and the surfactant are present in a synergistic ratio with respect to the solubilization of aprepitant
Data Source
AI summary
An aqueous stable and ready-to-use formulation of aprepitant is prepared. Especially preferred formulations comprise a synergistic combination of a co-solvent and a surfactant and may further include a secondary co-solvent. Among other advantages of contemplated formulations, aprepitant is dissolved at high concentrations and remains dissolved and stable, even over prolonged periods of time.