Solid-State and Solution-Mediated Polymorphic Transformation of Rifampicin

Rifampicin, a semisynthetic broad-spectrum antibiotic with antibacterial activity for a variety of pathogenic microorganisms, has three crystal forms, namely, I, II, and SV. Forms I and II are bioavailable. Solid-state polymorphic transformation (SST) from FormII to I and solution-mediated polymorphic transformation (SMT) from FormI to II were investigated by offline X-ray diffraction (PXRD) and Fourier transform infrared spectroscopy (FTIR), respectively. Solubility and supersolubility of rifampicin FormsI and II in different solvents were obtained using the static method and turbidity meter method separately. The thermodynamic study of rifampicin proved that crystal FormI was more stable than FormII. These studies were necessary to optimize the crystallization process and crystal form controlling. The bulk density which influences significantly the drug loading capacity was clearly developed.