Abstract
The decomposition rates of p-aminosalicylic acid were measured in four samples, recrystallized crystals, ground crystals, physical mixture with microcrystalline cellulose and ground mixture with microcrystalline cellulose. The drug in the ground mixture is markedly unstable at 40°C as compared with the physical mixture and the recrystallized crystals. This instability could be attributed to the molecular-scale drug dispersion in the ground mixture together with the presence of sorbed water in the cellulose. At 80°C the ground crystals decomposed at a constant rate while the decompositiontime curves of the recrystallized crystals exhibited sigmoid characteristics. It is concluded that in the ground crystals, m-aminophenol formed does not act as autocatalytic nuclei.
