Prediction of Optimum Combination of Eudragit RS/Eudragit RL/Ethyl Cellulose Polymeric Free Films Based on Experimental Design for Using as a Coating System for Sustained Release Theophylline Pellets

摘要

Purpose: The physicochemical properties of free films made fromdifferent mixtures of sustained release polymers were investigated, and an optimum formulation coating on drugcontaining pellets, based on the study of free film was evaluated.Methods: In order to determine the effect of differentvariables on the permeability and swelling of films and procedure optimization,the experimental design was fulfilled based on the statistical method of a 33full factorial design, and according to this method 27 formulations wereprepared. The films were prepared using casting-solvent evaporation method.Water vapor permeability, the swelling and permeability of free films in bothacidic and buffer media, were carried out. Then, the pellets containingtheophylline were coated with the optimum formulation.Results: The results of this study demonstrated that anincrease in the free film thickness and Eurdragit RS ratio in films lowered thewater vapor transmission (WVT), the swelling and the permeability of allformulations, while an increase in the quantity of ethylcellulose, up to aspecific ratio (approximately 40%), decreased the permeability and swelling.The most optimum free film formulation was made up of 60% Eudragit RS and 40% ethylcellulose.Conclusion: Pellets coated with a 10% coating level ofethylcellulose and Eudragit RS (4:6) showed suitable release properties andcould serve as a favorable sustained release system for theophylline.