PREPARATION AND EVALUATION OF SUSTAINED-RELEASE MICROSPHERES OF TERBUTALINE SULFATE

Terbutaline sulfate (TBS) microspheres were prepared from Eudragit RS(R) by an emulsion-solvent evaporation method. In the presence of aluminium tristearate, used as a smoothing agent, the micropellets formed were very spherical and their size distribution was within a narrow range. The mean size of microspheres decreased as the polymer/drug ratio increased. The microspheres showed pH-independent dissolution behavior. As the mean size of microspheres decreased, the release of TBS was retarded. Maximum retardation occurred with 5% aluminium tristearate. The microspheres formulated at a polymer/drug ratio of 9:1 produced a typical 12 h sustained release pattern. Compared with commercial TBS of the PVC matrix type, the microspheres showed equivalent release characteristics.