Pharmaceutical cocrystal and salts of norfloxacin

The aim of this study was to investigate the structural and pharmaceutical properties of norfloxacin ( a poorly soluble antibacterial drug), its cocrystal, and salts. Norfloxacin in the anhydrous form ( form A, 1) was crystallized. It was cocrystallized with isonicotinamide ( 2), and organic salts were prepared with succinic acid, malonic acid, and maleic acid (3-5, respectively). These phases were characterized by differential scanning calorimetry (DSC), infrared (IR) and Raman spectroscopy, and powder X-ray diffraction (PXRD). Single-crystal X-ray diffraction data were obtained, and crystal structures were solved. The apparent solubility of these phases was determined. Robust O-H center dot center dot center dot O, O-H center dot center dot center dot O-, O-H center dot center dot center dot N, N-H center dot center dot center dot O, N+- H center dot center dot center dot O-, and N-H center dot center dot center dot N interactions were present in all these structures. Quinolone moieties in these structures stack with pi...pi interactions and form channels to include CHCl3 or H2O. Herein we report a new cocrystal and salts of norfloxacin with improved aqueous solubility.