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Abstract
The aim of this study was to statistically optimize the use of blends of methacrylic acid ester copolymers with different permeability properties as controlled-release coating systems for tablets to produce predictable predesigned release profiles. A full factorial design was used to study and optimize the use of methacrylic acid ester copolymers Eudragit® RS 30D and Eudragit® RL 30D as coating materials for controlled release. Directly compressed theophylline tablets were coated with aqueous dispersions containing different proportions of the two copolymers using a side-vented coating pan (Accela Cota®). The effect of polymer loading level at 5, 7.5, and 10% weight gain and curing time at 50°C for 12 and 24 hours were also evaluated. Coated tablets were tested for their drug release in water using a United States Pharmacopeia (USP) dissolution apparatus #2. The results showed that increasing the content of the lower permeability copolymer Eudragit® RS 30D, increasing the polymer load, and increasing curing time at 50°C resulted in slower drug release. A statistical model that describes and predicts the drug release properties of the coated tablets as a function of the copolymers ratio in the coating dispersion, polymer load, and curing time at 50°C was developed. The most significant factor affecting drug release was found to be the ratio of the two copolymers in the coating dispersion followed by the curing time at 50°C and the polymer loading level. Good correlations were observed between the model fitted values and the experimental values. An optimized formula prepared by superimposing two-dimensional contour plots was prepared; its release profile was found to be in agreement with the prediction obtained from the model.