Drug Solubility Prediction in Polymers Using Thermal Analysis
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Solution Overview
Problem
There is no standard method to determine or predict the solubility of drugs in solid polymers, especially at room temperature or below, due to low mobility of drug molecules, making experimental determinations impractically long and challenging.
Innovation Solution
A method using thermal analysis methods like differential scanning calorimetry (DSC) in conjunction with published equations to predict drug solubility without waiting for equilibration, allowing for solubility determination at various temperatures, including storage temperatures, by calculating specific enthalpy and entropy differences between solid solutions and unmixed components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If experimental determination of drug solubility in solid polymers is performed at room temperature, then the solubility prediction is relevant to storage conditions, but the experimental time becomes impractically long due to low molecular mobility
Solution Approach 1:
The patent applies preliminary action by conducting solubility experiments at elevated temperatures where molecular mobility is higher and equilibration occurs faster, then using thermodynamic relationships to predict the solubility at storage temperatures. This allows the determination to be completed in reasonable time while still providing relevant storage condition data.
Solution Approach 2:
The patent changes the temperature parameter from room temperature to elevated temperatures during the experimental determination phase. By measuring solubility at multiple elevated temperatures and using the van't Hoff relationship, the method predicts solubility at storage temperatures, thus avoiding the impractically long wait times at room temperature while maintaining predictive accuracy.
2Productivity
If elevated temperatures are used to accelerate equilibration, then the experimental time is reduced, but chemical degradation of the drug may occur
Solution Approach 1:
The patent uses partial action by conducting experiments at moderately elevated temperatures rather than extreme temperatures, and for limited time periods. The thermodynamic extrapolation allows using less extreme conditions than would be required if waiting for full equilibration at room temperature, thus achieving reasonable throughput while minimizing degradation risk.
Solution Approach 2:
The patent replaces the direct physical equilibration process (which would take impractically long at room temperature) with a thermodynamic calculation approach. By measuring solubility at elevated temperatures and using the van't Hoff equation to extrapolate to storage temperatures, the method avoids prolonged exposure to conditions that could cause degradation while still obtaining accurate predictions.
3Measurement precision
If standard experimental methods are used to determine solubility, then the measurement is direct and accurate, but the method becomes complex and requires impractically long equilibration times
Solution Approach 1:
The patent changes the temperature parameter during measurement to facilitate faster equilibration, then uses thermodynamic relationships to correct for the temperature difference. This maintains measurement accuracy while simplifying the experimental procedure by avoiding years-long equilibration times that would be required at room temperature.
Solution Approach 2:
The patent performs preliminary measurements at elevated temperatures where equilibration is achievable in reasonable time, then uses thermodynamic extrapolation to obtain the solubility at storage conditions. This preliminary approach at favorable conditions avoids the impracticality of direct room temperature measurement while maintaining accuracy.
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
Enables the prediction of drug solubility in polymers at different temperatures without requiring impractically long experiments or elevated temperatures, providing important information for drug formulation and avoiding chemical degradation.
Implementation Method 1
determining the specific heat of the unmixed components in said ratio over a given range of temperatures; determining the specific heat of the solid solution over the said range of temperatures
Data Source
AI summary
The invention provides an improved method to predict the solubility of a drug or other molecule in a solid polymer or other matrix at any temperature. The instant invention provides a method to determine the difference in specific enthalpy, specific entropy and specific Gibbs energy between a solid solution and the unmixed components, as well as a method to use those data to predict the solubility of a drug or other molecule in a solid polymer or other matrix. The method uses known thermodynamics equations and thermal analysis data, such as obtained from DSC (differential scanning calorimetry) at temperatures that are lower than the temperature at which the solubility is predicted. The method allows prediction of the drug-in-polymer solubilities without the use of elevated temperatures, but still avoids impractically long experiments. The instant invention can predict the solubility at many temperatures, but is particularly useful in the pharmaceutical sciences to predict the solubility of a drug in a polymer at typical storage temperatures, which are typically near room temperature or below.