Design and evaluation of Coated Microspheres of Antiprotozoal drug for colon specific delivery

Colon-specific drug delivery has gained increased importance in the delivery of drugs for the treatment of local diseases associated with the colon, such as Crohn's disease, ulcerative colitis, colorectal cancer and amoebiasis. Metronidazole, an antiprotozoal drug is clinically effective in colonic diseases, both locally and systemically. The aim of this work was to prepare and evaluate Eudragit coated chitosan microspheres of metronidazole for colon targeting. Chitosan microspheres were prepared by emulsion dehydration method using different ratios of drug and polymer. Eudragit coated chitosan microspheres were performed by solvent evaporation method and were evaluated for percentage yield, flow property, particle size analysis, surface morphology, determination of drug content, drug entrapment efficiency, degree of swelling, in vitro drug release and its kinetic profile. The percentage yield of all formulations was more than 80%. The microspheres showed a spherical structure with a smooth surface morphology. The drug entrapment efficiency was found to be in between 68.8%-81.6%. The in vitro release was found to be in following order F3>F1>F2>F4>F5>F6. In the case of F3 only 13.03% of the drug was released in 5 hrs, but it showed high and fast increase in drug release from 6th hr in pH 6.8 phosphate buffer. It shows 90.52% drug release after 12hrs.The formulations gave good fit to the Zero order and the mechanism of drug release was diffusion. The results clearly demonstrated that the Eudragit S100 coated metronidazole chitosan microspheres is a potential system for colon-specific drug delivery.