Formulation and optimization of rifampicin microparticles by Box-Behnken statistical design

The objective of the present study was to optimize and evaluate in vitro gastroretentive performance of rifampicin microparticles. Formulations were optimized using design of experiments by employing a 4-factor, 3-level Box-Behnken statistical design. Independent variables studied were the ratio of polymers (Eudragit RSPO: ethyl cellulose), inert drug dispersing agent (talc), surfactant (sodium dodecyl sulfate) and stirring speed. The dependent variables were particle size and entrapment efficiency. Response surface plots were drawn, statistical validity of the polynomials was validated and the optimized formulation was characterized by Fourier Transform-InfraRed spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Entrapment efficiency and particle size were determined. The designed microparticles have average particle size from 14.10 μm to 45.63 μm and entrapment efficiency from 38.14% to 94.81%. Optimized microparticles showed particle size and drug entrapment, 51.53 μm and 83.43%, respectively with sustained drug release behavior up to 12 h. In the present study, rifampicin microspheres were successfully prepared by a quasi-emulsion solvent diffusion technique for prolonged drug release. FT-IR and DSC studies did not reveal any significant drug interactions. The drug release was found to be controlled for more than 12 h by following zero order release pattern.