Three polymorphic modifications and one amorphous form were prepared by recrystallization under various conditions and characterized by DSC and X-ray crystallography. At $37{pm}0.5^{circ}C$, the polymorphic modifications showed significant differences in the dissolution rate. The dissolution rate of Mod. 4, amorphous form, was faster than that of other polymorphic modifications. When all modifications were stored at 52% RH, 95% RH, and in silica gel desiccator, amorphous form was transformed at 95% humidity condition.