Sparfloxacin is more bactericidal than ofloxacin against Mycobacterium leprae in mice

The comparative bactericidal activities of sparfloxacin and ofloxacin against Mycobacterium leprae in mice were determined using the proportional bactericidal test at doses of 12.5 mg/kg-100 mg/kg. Significant bactericidal activity was found at 12.5 mg/kg sparfloxacin and 25 mg/kg ofloxacin. Sparfloxacin was significantly more bactericidal than ofloxacin at all doses, and the results with 25 mg/kg sparfloxacin were nearly identical to those obtained with 100 mg/kg ofloxacin. These results, together with pharmacokinetic and toxicological data in mice and man, suggest that sparfloxacin may have a higher therapeutic index than ofloxacin in leprosy, and that the tentative standard dosage of 200 mg sparfloxacin daily should be appropriate for a clinical trial.