Famotidine polymorphic transformation in the grinding process significantly depends on environmental humidity or water content.

The effect of environmental humidity and additional water added on the polymorphic change of famotidine in the process of grinding was investigated. The famotidine form B powder with or without additional amount of water added was respectively ground for 30 min in an oscillatory ball mill under 25+/-2 degrees C and three relative humidities (RH) (50+/-5%, 75+/-5% or 95+/-5% RH). Each ground sample was periodically isolated for analytical determinations by using differential scanning calorimetry (DSC), thermogravimetric (TG) analysis and Fourier transform infrared (FT-IR) microspectroscopy. The results indicate that the higher environmental humidity might induce and promote the polymorphic transformation of famotidine from form B to form A in the process of grinding. Moreover, the more the amount of water externally added the easier the polymorphic transformation of famotidine from form B to form A obtained. In addition, the more grinding time spent the more formation of form A obtained. This study disavowed the results of other studies in which no polymorphic change of famotidine even by grinding. The apparent evidence shows that the solid-state polymorphic transformation of famotidine from form B to form A in the grinding process significantly depended on the relative humidity of atmosphere and the additional amount of water added.