Transformation of Cocrystalline Phase in Binary Mixture of Trimethoprim and Sulfamethoxazole by Slurry Technique

The purpose of this work was to characterize and investigate the transformation of cocrystalline phase in binary mixture of trimethoprim and sulfamethoxazole induced by slurry technique and to establish the rate of transformation at various temperatures. Cocrystallization was performed simply by adding distilled water as solvent to equimolar binary mixture of powder trimethoprim and sulfamethoxazole. A new solid phase was characterized by thermomicroscopy, scanning electron microscope, powder X-ray diffraction, differential scanning calorimetry. The rate of transformation in slurry was studied as function of storage temperature, measured by powder X-ray diffractometry. Physical characterization showed that the trimethoprim and sulfamethoxazole cocrystalline phase had a unique thermal, powder X-ray diffraction property. Cocrystals prepared by slurry technique were similar in PXRD pattern to those prepared by solvent methods. The transformation to cocrystalline phase was accelerated by increasing the temperature of storage. It could be concluded that slurry could be carried out to induce a new equimolar cocrystalline phase between sulfamethoxazole and trimethoprim. The rate of transformation to cocrystalline phase was affected by the temperature of storage. Keywords: Trimethoprim; sulfamethoxazole; cocrystalline phase; slurry technique and rate of transformation.