Biopharmaceutical studies on sulphadimidine modifications

The authors studied sulphadimidine crystal forms with particular reference to the occurrence of polymorphism. They were able to differentiate five crystalline forms by microscopic examination. Differential thermal analysis and IR absorption spectral methods were not reliable. The data from X-ray diffraction patterns of two crystal forms (methanol form I, ethanol form II) were reproducible by estimating their relative intensities. The crystal forms investigated were compared by in vitro and in vivo experiments. Experiments showed that sulphadimidine crystals recrystallized from ethanol had better dissolution and absorption characteristics than sulphadimidine crystals recrystallized from methanol.