The objective was to prepare an Enalapril maleate (EnM) loaded floating microsphere with minimum particle size, maximum drug loading and drug entrapment efficiency. Formulations were prepared by varying drug-polymer ratio (A), solvent-ratio (B), and stirring time (C). Solvent evaporation method was used to prepare the microsphere. "Box-Behnken design (3-factor, 3-level)" was utilized for the optimization. The independent variables were polymer-drug ratio (A), solvent-ratio (B), and stirring time (C) while particle size (R1), drug loading (R2), and entrapment efficiency (R3) were considered as dependent variables. EnM-loaded alcohol microsphere (Formulation-A) was prepared and optimized and both Formulation-A and EnM-loaded acetonitrile microspheres (Formulation B) were subjected for the morphological, micrometric, characterization and in vitro release study. The particle size, drug loading and entrapment efficiency of Formulation-A and Formulation-B were 143±27.75µm, 37.31±5.73%, 76.89±4.97%, and 158.13±25.1µm, 40.13±6.12% and 99.19±1.14% respectively. The cumulative drug release of the Formulation-A and Formulation-B were 90.52±4.11%, and 86.23±3.81% respectively. Both formulations followed Higuchi model of drug release. EnM-floating microsphere was effectively prepared and both formulations showed excellent continuous release properties for more than 12 hours.
Key words: enalapril maleate, floating microsphere, box-behnken design, controlled release, solvent evaporation