In vitro drug liberation and kinetics of sustained release indomethacin suppository

The aim of this study was to formulate sustained release (SR) suppositories containing indomethacin (IND) microspheres. In the first part of the study, IND microspheres were prepared by solvent evaporation method. Ethyl cellulose was used as polymer. Shape and surface characteristics, particle size and size distribution of microspheres were determined. The effect of drug: polymer ratio and stirring rate on microsphere formation, average particle size, drug loading capacity and in vitro IND release were investigated. The highest drug loading capacity was found with 1:1 drug-polymer ratio. Stirring rate caused insignificant effect on drug loading capacity but particle size. Increase in stirring rate resulted in a decrease in particle size. In the second part, SR suppositories were formulated by incorporating IND microspheres having the highest drug loaded. The bases used were PEG mixtures (400:1500:4000) and Witepsol H15. Qualitative controls and IND assay on the suppositories were carried out. The drugs released were evaluated by in vitro dissolution tests. Comparative results of SR suppositories containing IND microspheres with that of conventional ones showed that the former has sustained effect up to 480 min in vitro. Release results were evaluated kinetically and the data was fitted (Bt)(a) kinetics.