Coloration and photolytic degradation of some sulfonamide tablets under exaggerated and ordinary ultraviolet irradiation.

Abstract

Five sulfonamide tablets, those of sulfaphenazole, sulfadimethoxine, sulfisomidine, sulfisoxazole, and sulfamethizole, were exposed to exaggerated and ordinary ultraviolet (UV) rays for stability studies in the solid state, and the relationship between coloration stability and chemical degradation was investigated. The color change of tablet surface was measured by colorimetric method. Sulfisoxazole and sulfamethizole were photostable in coloration, and sulfadimethoxine was eventually not colored contrary to what was stated in the Pharmacopeia of Japan. Photosensitive similarity between exaggerated and ordinary exposure was not established in coloration. Photolytic degradation was examined spectrophotometrically and crystallographically. Interesting absorption changes were observed in UV spectra, whereas no apparent changes in either infrared spectra or X-ray diffraction patterns. These evidences were discussed in relation to the results obtained by the complementary tristimulus colorimetry using the UV absorption data. For all the sulfonamides, evident correlation did not exist between coloration and photolytic degradation.