Abstract
Purpose: The physicochemical properties of free films made from
different mixtures of sustained release polymers were investigated, and an optimum formulation coating on drug
containing pellets, based on the study of free film was evaluated.
Methods: In order to determine the effect of different
variables on the permeability and swelling of films and procedure optimization,
the experimental design was fulfilled based on the statistical method of a 33
full factorial design, and according to this method 27 formulations were
prepared. The films were prepared using casting-solvent evaporation method.
Water vapor permeability, the swelling and permeability of free films in both
acidic and buffer media, were carried out. Then, the pellets containing
theophylline were coated with the optimum formulation.
Results: The results of this study demonstrated that an
increase in the free film thickness and Eurdragit RS ratio in films lowered the
water vapor transmission (WVT), the swelling and the permeability of all
formulations, while an increase in the quantity of ethylcellulose, up to a
specific 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 of
ethylcellulose and Eudragit RS (4:6) showed suitable release properties and
could serve as a favorable sustained release system for theophylline.