Stability studies of aspirin-magaldrate double layer tablets

Accelerated stability testing was performed on aspirin-magaldrate double layer tablets as well as aspirin-maalox marketed double layer tablets (Ascriptin) in order to evaluate the effect of the presence of the alkaline moieties of the antacid (magaldrate and maalox) on the chemical stability of aspirin. The results were compared simultaneously with that obtained from the marketed Aspro plain tablets. The results revealed that the presence of the alkaline moieties in the tested tablets has increased the rate of aspirin decomposition and reduced its shelf-life. This effect was more pronounced for aspirin tablets containing magaldrate antacid. Determination of shelf-lives at 25 degrees C for the prepared and the marketed tablets was carried out using Arrhenius plots and the results showed that they were 35, 34.5 and 13.5 months for Aspro, Ascriptin and aspirin-magaldrate double layer tablets, respectively. The effect of storage for 50 days and at different temperatures, on the crushing strength and the disintegration time of the prepared and the marked tablets showed a slight decrease in the disintegration time and the crushing strength of the tablets as the storage temperature increased. Aspro tablets did not produce the same results. The in vitro release data of the prepared aspirin-magaldrate double layer tablets and the marketed Ascriptin tablets stored for 50 days and at different storage temperatures as well as Aspro tablets stored at 70 degrees C were best fitted to the first-order kinetics model. The release data of Aspro tablets stored at 50 and 60 degrees C for 50 days were best fitted to Higuchi's model.