Preparation and evaluation of microspheres with dual polymeric film to minimize burst effect of highly water soluble drug

Double-layered controlled release microspheres of venlafaxine were prepared using ethyl cellulose (EC) as a wall forming hydrophobic polymer. Usually, it is difficult to control initial sudden release of highly water-soluble drugs. In this regard, double-layered microparticles were prepared not only for controlling initial burst effect but also to sustain the release of venlafaxine for an extended period of time. Solvent evaporation technique based on O/O emulsion was applied to prepare modified release microparticles. To minimize initial burst effect, developed microparticles were again coated with same hydrophobic polymer. Percent recovery, drug loading efficiency and particle size were measured. FTIR, SEM and kinetic models were applied to characterize venlafaxine microspheres. Packing and flow properties of microparticles were satisfactory. FTIR spectra of EC, venlafaxine and venlafaxine loaded microspheres were recorded. SEM analysis showed the formation of spherical microspheres with slightly rough surface. Burst effect of venlafaxine was significantly retarded in double-layered microparticles. Drug release databased on highest values of correlation coefficient, was suitably explained by Higuchi kinetics and mechanism of release was Fickian diffusion. This study strongly suggests that double-layered microspheres can successfully be applied for controlling the dose dumping and sustaining the release of highly water-soluble drug for an extended period of time.