Cinnarizine is an ideal candidate for incorporation in a controlled release device to diminish its adverse effects after oral administration. Microspheres were prepared by using ethyl cellulose as a polymer and CaCl2 as a cross-linking agent. In this investigation, a 32 full factorial design was applied to investigate the combined effect of two formulation variables, each at 3 levels and the possible 9 combinations of cinnarizine microspheres were prepared. The amount of Ethyl cellulose (X1) and the amount of PVA (X2) were taken as independent variables. The entrapment efficiency is taken as dependent variables. Contour plots are presented to visualize the impact of independent variables on the entrapment efficiency in the microspheres. It was observed that entrapment efficiency was dependent on both the factors. The entrapment efficiency is influenced by the change in the EC ratios. The diameter of the microspheres showed poor correlation with the selected independent variables. All the batches yielded microspheres with excellent topographical characteristics. The entrapment efficiency for the 9 batches showed a wide variation (ie, 16.39% and 54.17%). The diameter of the microspheres was not found to be dependent on the type and amount of polymers used for the preparation of microspheres. The diameter range of the prepared microspheres was 321.02 µm to 484.35 µm. Five kinetic models including the zero order, first order, Higuchi matrix, Korsmeyer Peppas and Hixson Crowell release equations were applied to process the in-vitro release data to find the equation with the best fit. All the formulations follow the Higuchi equation. Hence, the release is through diffusion mechanism. The results of analysis of variance test, for drug content in microspheres, indicated that the test is significant. The drug was released by diffusion of anomalous type. Acceptable batches were identified in the experimental design with constraints on percentage drug released.
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