Levofloxacin was prepared by reacting (S)-(-)-9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid with N-methyl piperazine in a polar solvent or in a neat mixture to form levofloxacin. Further processing of the levofloxacin produced novel levofloxacin forms, including a hemihydrate and Forms A, B, C, F, G and H.

Levofloxacin was prepared by reacting (S)-(-)-9,10-difluoro-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine-6-carboxylic acid with N-methyl piperazine in a polar solvent or in a neat mixture to form levofloxacin. Further processing of the levofloxacin produced novel levofloxacin forms, including a hemihydrate and Forms A, B, C, F, G and H.

Levofloxacin has been purified by dissolving levofloxacin in a polar solvent at an elevated temperature and crystallizing purified levofloxacin. Preferably, an antioxidant is added to increase the purity.