[Stability of probucol-polyvinylpyrrolidone solid dispersion systems].

After solid dispersion systems of probucol-polyvinylpyrrolidone K30 (1 : 9 in weight ratio) were exposed to light (10000 lx) for 7 days, 84% of the probucol remained. Commercial probucol fine granules were thus fairly stable under light exposure. When solid dispersion systems were stored in heat-sealed packages at relative humidity (R.H.) of 75% and 92% for 30 days at 30°C, the weight of the samples increased by 22% and 43%, respectively. When these solid dispersion systems were dissolved in water, the probucol concentration decreased with the duration of storage. The crystalline nature of probucol in the solid dispersion systems could not be detected by powder X-ray diffraction or differential scanning calorimetry. After passing the dissolution medium through the membrane filter, retention time of the residue on the filter in the HPLC method corresponded to that of probucol. These results suggest that the partial crystallization of probucol in the solid dispersion systems may occur during storage under these conditions. Solid dispersion systems in heat-sealed packages were fairly stable when stored under room conditions or in light-resistant tightly sealed containers for 5 months.