Photo-stability of the new antiplatelet agent, KBT-3022 (ethyl 2-[4,5-bis(4-methoxyphenyl)thiazole-2-yl]pyrrol-1-ylacetate) in aqueous solutions containing acetonitrile.

The photo-stability of ethyl 2-[4,5-bis(4-methoxyphenyl)thiazole-2-yl]pyrrol-1-ylacetate, KBT-3022 in aqueous solutions containing acetonitrile was investigated under the light of a high pressure mercury lamp. Its main photo-degradation product was assumed to be ethyl 5-hydroxy-5-[4,5-bis(4-methoxyphenyl)thiazole-2-yl]-2-oxo-3-pyrrolin+ ++-1-ylacetate. KBT-3022 was also found to undergo ester hydrolysis by heat in both acidic and basic aqueous solutions, but its hydrolysis was confirmed to be negligible in the range of pH 3-9 at room temperature (25 degrees C). Further, its photo-stability with exposure to the high pressure mercury lamp was comparable to that with exposure to a fluorescent lamp. Therefore, it is considered feasible to simulate the photo-stability of KBT-3022 in aqueous solutions containing acetonitrile by exposure to all other light sources including diffuse daylight, if the cumulative number of photons of the light can be determined by actinometry.