THE PREPARATION AND CHARACTERIZATION OF SOLID DISPERSIONS ON PELLETS USING A FLUIDIZED-BED SYSTEM

In this study, solid dispersions of a poorly water-soluble drug, nifed ipine, were prepared in hydroxypropylmethylcellulose (HPMC) on sugar s pheres using a fluidized-bed coating system and characterized by diffe rential scanning calorimetry (DSC) and dissolution measurements. A mix ture of acetone and water (7:3) was found to be suitable as a spraying solution for simultaneous application of nifedipine and HPMC. DSC stu dies showed that the peak corresponding to the melting point of nifedi pine became broadened when nifedipine was incorporated in a solid disp ersion with HPMC at both ratios of 1:1 and 1:3. The results demonstrat ed that dissolution rates were fastest at. the lowest nifedipine loadi ng. Furthermore, the dissolution rate of nifedipine increased as more HPMC was added to the solid dispersions. The enhancement in the dissol ution rate of nifedipine upon addition of Tween 80 in simulated gastri c acid was attributed to the solubilizing effect of Tween 80 on nifedi pine. Tween 80 had less influence when nifedipine was incorporated in solid dispersions containing higher fractions of HPMC.