Formulation And Evaluation Of Floating Gastroretentive Microsphere Of Antiviral Agent (Acyclovir)

Abstract

This study focuses on the formulation and evaluation of floating gastroretentive microspheres containing the antiviral agent acyclovir. The aim is to enhance the bioavailability and therapeutic efficacy of acyclovir by prolonging its gastric residence time. Microspheres were prepared using the solvent evaporation method, employing different polymers such as ethyl cellulose, and carbopol 934P to achieve sustained release and buoyancy.Various formulations were developed by altering the polymer concentration and drug-to-polymer ratios. The prepared microspheres were evaluated for particle size, surface morphology, drug loading, entrapment efficiency, in vitro buoyancy, and in vitro drug release. Particle size analysis indicated that the microspheres were in the range of 150-300 micrometers. Scanning electron microscopy (SEM) revealed that the microspheres were spherical with a smooth surface.The drug entrapment efficiency of the microspheres ranged from 60% to 85%, and the buoyancy tests demonstrated that more than 75% of the microspheres remained floating for over 12 hours. In vitro drug release studies were conducted in simulated gastric fluid (pH 1.2) using a USP type II dissolution apparatus. The results showed a sustained release of acyclovir from the microspheres, with drug release extending up to 12 hours, depending on the formulation. The optimized formulation, which contained HPMC as the primary polymer, exhibited a desirable balance between buoyancy and sustained release, with an entrapment efficiency of 82% and 88% of the microspheres remaining buoyant for 12 hours. The release kinetics followed a non-Fickian diffusion model, indicating that drug release was controlled by both diffusion and polymer erosion.