A PRAGMATIC APPROACH ON COLONIC DELIVERY OF RIFAXIMIN USING POLYMER COATED MULTI-PARTICULATE SYSTEM

This study aimed to develop and optimize a multi-particulate formulation for colon targeted delivery of rifaximin by application of a functional coat of Eudragit L100 and Eudragit S100 mixture on the drug layered pellets. The rifaximin-excipients compatibility was confirmed with FTIR studies. Functional coat completely restricted drug release in pH 1.2 dissolution medium.  Statistical optimization of the formulation variables, i.e., ratio of Eudragit L100 and S100, and % of coating, in respect to drug release at 2^nd and 8^th h in pH 6.8 dissolution medium was conducted with a central composite design and response surface methodology. Compared to % of coating, the impact of polymer ratio was more pronounced for modulating the drug release. Comparatively, higher influence of % coating was observed after 2 h of dissolution. As per graphical optimization, the minimum drug release at 2^nd h and maximum drug release at 8^th h could be achieved in formulation with 3.3 polymer ratio and 15.4 % coating where more than 80 % of drug should be delivered in colon. The high efficacy of the optimized formulation on colonic delivery of rifaximin was further confirmed with the animal study. Findings of this study indicate that application of Eudragit L100 and Eudragit S100 coating in an appropriate ratio on drug layered multi-particulates could be a promising approach for colonic delivery of rifaximin