Compatibility between Drugs and Photodegradation of Sustained Release Fine Granules of Nifedipine

Compatibility of sustained-released fine granules of nifedipine (SRN) with 21 kinds of drug were studied. The mixtures of SRN and drugs in heat-sealed packages (polyethylene-laminated glassine paper) were kept at 20°C and 75% relative humidity (R. H.) or 30°C and 92% R. H. for 30 days. Weight change and color of samples were recorded. Dissolution tests of nifedipine from the mixtures of SRN and the drugs were studied in J. P. disintegration media No.1 and No.2. Significant incompatibility was not observed in the weight change, nor was significant change of dissolution of nifedipine noted except for the combination with sodium bicarbonate. Dissolution of nifedipine was enhanced by sodium bicarbonate in disintegration medium No.1. We further studied photodegradation of nifedipine in SRN. Fluorescent light was irradiated (1000 lx) on SRN in a petridish wrapped with polyvinylidenchloride film, in a heat-sealed package, in a heat-sealed package kept in a paper bag, and in a heat-sealed package kept in a light-resistant multi-layered laminate bag. Except for the light-resistant bag, light irradiation produced considerable unstability in nifedipine in SRN.