Esterified Cellulose Ether Viscosity Control for Drug Solubility
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Solution Overview
Problem
Existing esterified cellulose ethers with high molecular weight exhibit high viscosity in organic solvents, making them inefficient for spray-drying and coating processes, which are necessary for pharmaceutical dosage forms, especially for drugs with low solubility, as they tend to clog equipment and require complex techniques to minimize solvent removal.
Innovation Solution
Development of esterified cellulose ethers with a weight average molecular weight of at least 220,000 to 350,000 Daltons and viscosity up to 50 mPa·s in acetone, achieved through specific reaction parameters such as molar ratios of aliphatic carboxylic acid to dicarboxylic acid anhydride and the use of alkali metal carboxylates, allowing for efficient processing without excessive viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high molecular weight esterified cellulose ethers are used, then resistance against gastric juice is improved, but viscosity in organic solvent increases making coating processes inefficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the weight average molecular weight (220,000-500,000 Daltons) and viscosity (up to 100 mPa·s in acetone) of the esterified cellulose ether to resolve the contradiction between gastric resistance and processability. This optimization allows the polymer to maintain high molecular weight for gastric resistance while limiting viscosity for efficient spray-drying and coating
Solution Approach 2:
The patent uses composite materials by combining esterified cellulose ether with specific solvents (acetone, ethyl acetate, isopropyl alcohol) and active ingredients to create optimized coating compositions. This composite approach enables the polymer to function effectively at controlled concentrations (5-50 wt%) while maintaining both gastric resistance and processing efficiency
2Loss of substance
If high concentration of esterified cellulose ether in organic solvent is used, then solvent removal is minimized, but viscosity increases causing equipment clogging
Solution Approach 1:
The patent optimizes the concentration parameter of esterified cellulose ether in organic solvent to between 5-50 wt%, with viscosity controlled up to 100 mPa·s. This parameter optimization allows high solid content formulations that minimize solvent removal while maintaining pumpable consistency and preventing equipment clogging during spray-drying and coating operations
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 resulting esterified cellulose ethers enable high molecular weight with reasonably low viscosity, facilitating efficient spray-drying and coating processes, improving the bioavailability of poorly soluble drugs by reducing crystallinity and enhancing solubility, while minimizing solvent usage and equipment clogging.
Implementation Method 1
establishing hydrophilic conditions around the drug molecules, thereby improving the solubility of the drug itself
Implementation Method 2
establishing hydrophilic conditions around the drug molecules, thereby improving the solubility of the drug itself to increase its bioavailability
Data Source
AI summary
Esterified cellulose ethers which comprise (i) groups of the formula -C(O) - R - COOA or (ii) a combination of aliphatic monovalent acyl groups and groups of the formula -C(O) - R - COOA, wherein R is a divalent aliphatic or aromatic hydrocarbon group and A is hydrogen or a cation, which have a viscosity of up 50 mPa.s, measured as a 10 wt% solution of the esterified cellulose ether in acetone at 20°C, and a weight average molecular weight Mw of at least 220,000 Dalton, or which have a viscosity of up 100 mPa.s, measured as a 10 wt% solution of the esterified cellulose ether in acetone at 20°C, and a weight average molecular weight Mw of at least 310,000 Dalton are useful for preparing solid dispersions comprising drugs.