Dissolution behaviour of sustained release formulations of indomethacin with Eudragit RS

This study investigates the kinetics of the release of indomethacin from Eudragit RS polymer. It involved the study of the dissolution behaviour of indomethacin from different combinations of the drug in a solid dispersion form, granules and physical mixtures. It was evident that Eudragit RS had a retardation effect on the release of indomethacin, this effect was dependent on the amount of Eudragit included. Inclusion of sodium lauryl sulphate (SLS) in the solid dispersion, granules and physical mixtures modified the release and made it comparable to the release from Indocid retard capsules. The kinetics of the release process was found to be best described by the Higuchi square root of time equation and the first order equation indicating that the release process is diffusion controlled and dependent on the initial drug concentration. The retarding effect Eudragit had on the release of indomethacin was attributed to the possible interaction of the ammonium groups of the polymer with the carboxylate anion of indomethacin and to the inclusion of the drug within the inert insoluble polymer matrix.