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···O, O−H···O-, O−H···N, N−H···O, N+−H···O-, and N−H···N interactions were present in all these structures. Quinolone moieties in these structures stack with π···π interactions and form channels to include CHCl3 or H2O. Herein we report a new cocrystal and salts of norfloxacin with improved aqueous solubility.