Aspirin stability in solid dispersion binary systems.

The stability of aspirin in its solid dispersion with urea or povidone was investigated at two accelerated storage conditions. The observed aspirin degradation in both systems followed the first-order rate equation. The water sorption ability of the two carriers as well as the alkalinity imparted by urea could possibly be the most important factors responsible for the observed acceleration of aspirin decomposition. The results also showed that the temperature effect was more pronounced than the humidity effect. Generally, coprecipitated samples exhibited slightly higher degradation rates than physically mixed ones.