A trial for the design and optimization of pH-sensitive microparticles for intestinal delivery of cinnarizine

The aim of this study was to formulate a microparticulate delivery system to deliver cinnarizine (CIN) directly to its site of absorption to overcome its low oral bioavailability. Enteric microparticles were prepared by varying ratios of pH-sensitive polymers (Eudragit L100 and Eudragit S100). A full 33 factorial experimental design was adopted to evaluate the effect of variables (CIN concentration as well as Eudragit's concentration) on the tested parameters, namely, particle size (p.s.), drug entrapment efficiency (E.E.), and release efficiency (R.E.). Optimization was done using Design Expert (R) software to maximize E.E. and R.E. and minimize p.s. The optimized formula was characterized using scanning electron microscopy, differential scanning calorimetry, and X-ray diffractometry. In vivo studies conducted on human volunteers using LC-MS analysis revealed improved bioavailability of CIN-loaded enteric microparticles compared to the market product as detected from calculated pharmacokinetic parameters. This study reveals the usefulness of site-specific delivery of CIN.