Preparation, characterization and in vitro drug release of isosorbide dinitrate microspheres

Microspheres of isosorbide dinitrate (ISDN) were prepared using the emulsification/solvent evaporation method. The impacts of different factors such as stirring rate, concentration of ethyl cellulose (EC) as matrix polymer, poly vinyl chloride (PVA) as stabiliser and ISDN on the characteristics of the microspheres were investigated. The morphology of microspheres was studied using optical and scanning electron microscopy and it was shown that microspheres had a spherical shape and smooth surface. The particle size distribution of microspheres, analysed by a sieving method, was affected by stirring rate and concentrations of EC, PVA and ISDN. Larger microspheres showed greater drug loading and smaller microspheres showed a faster drug release. The in vitro drug release from microspheres was predictable and reproducible, conforming to the Higuchi model of release kinetics.