In vitro Evaluation of Nateglinide-Loaded Microspheres Formulated with Biodegradable Polymers

Purpose: To formulate and evaluate sustained release microspheres of nateglinide (NTG) for enhanced patient compliance. Methods: Nateglinide microspheres were prepared with varying proportions of biodegradable polymers (olibanum gum and guar gum) by calcium chloride/sodium alginate ionic gelation method. The microspheres were characterized by micromeritic analysis, particle size analysis, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and in vitro drug release studies. Yield and encapsulation efficiency were also evaluated while drug release data were subjected to various kinetic models. Results: Micromeritic analysis showed good flow properties of the microspheres while yield and microsphere size were in the range of 70 to 80 % and 781 to 842 mu m, respectively. FTIR and DSC results indicate the absence of drug-polymer interactions while SEM revealed that microspheres were almost spherical shape and porous in nature. Drug release was sustained in simulated intestinal fluid (pH 7.2), extending up to 10 to 12 h with greater release retardation in microspheres containing olibanum gum. The release pattern followed Higuchi kinetics model with non-Fickian diffusion. Conclusion: Suitable microspheres for sustained release of nateglinide can be formulated by ionic gelation method.