Further studies of the killing of M. leprae by aminoglycosides: reduced dosage and frequency of administration.

The bactericidal activity of the aminoglycoside antibiotics streptomycin and kanamycin for Mycobacterium leprae in mice was assessed, both alone and in combination with rifampin, utilizing various dosage schedules. As in previous studies, 100 mg/kg five times weekly of streptomycin and kanamycin resulted, respectively, in 96% +/- 2% and 89% +/- 6% bactericide. Reducing the dosage of streptomycin to 50 mg/kg, 25 mg/kg, and even 12.5 mg/kg resulted in less but significant bactericidal activity. Such a reduction of kanamycin dosage resulted in no significant bactericidal activity. Reducing the frequency of administration of streptomycin (100 mg/kg) to twice weekly and once weekly resulted in a decreased but still significant killing of M. leprae; for kanamycin such a reduction in frequency of administration resulted in loss of bactericidal activity. Streptomycin when combined with rifampin was found more bactericidal than either drug alone, even when each was administered only once monthly.