POLYMORPHISM AND STABILITY OF NORFLOXACIN, YDRO-4-OXO-7-(1-PIPERAZINIL)-3-QUINOLINOCARBOXYLIC ACID

Norfloxacin was studied by thermal methods (TG and DSC), X-ray powder diffraction, and by FT-IR, UV-VIS and NMR spectroscopy. The drug subst ance can be prepared in two different crystalline forms and in amorpho us state, depending on the experimental conditions of preparation. DSC examinations were carried out at various heating rates and by cycling the samples in the temperature range 50-degrees-250-degrees-C. The un stable crystalline form undergoes two irreversible solid-solid phase t ransitions at 176.5-degrees and 195.6-degrees-C. The polymorph melts i n the temperature range 218.5-degrees-220-degrees-C.