Eudragit FS based colonic microparticls of metoprolol tartrate

Metoprolol, a cardioselective β-blocker, is well absorbed in colon after oral administration with mean elimination half life of 3 h with bioavailability 50% due to extensive first pass effect, thus it was aimed to develop its modified release dosage form to reduce dosing frequency. Metoprolol tartrate loaded Eudragit FS microparticles were formulated using solvent evaporation technique by varying polymer contents and then compressing into tablets. The dissolution test was performed in simulated gastrointestinal fluid. All tabletted microparticles were tested for stability after storage in accelerated conditions. As a result of various analytical tests like FTIR, XRD and DSC analyses, drug was found stable in the microparticles. Metoprolol tartrate loaded Eudragit FS tabletted microparticles were stable in accelerated storage conditions. The release behavior of pH-dependent formulations was affected by the dissolution medium pH and the concentration of polymer used. There was a decrease in drug release rate with the increase in polymer concentration. In vitro drug release data (except test formulation F3) were best fitted to zero order model, which indicated the controlled release nature of formulation, while the Korsmeyer-Peppas model explored that drug release occurred according to case II relaxation transport mechanism (n > 0.89). Based on the results, it can be concluded that Eudragit FS is a suitable polymer to design pH dependent microparticles using solvent evaporation technique for the release of drug in colon and T2 can be considered as an optimum formulation on the basis of model independent (f2 test) kinetic interpretation of dissolution results (f2 < 50 for T2 versus reference).