Further experience with the rapid bactericidal effect of rifampin on Mycobacterium leprae

The effect of rifampin therapy in leprosy was studied in two clinical short-term trials in which skin punch biopsy specimens were taken at regular intervals for the inoculation of mice in order to monitor the decrease in proportion of viable Mycobacterium leprae in the patients' lesions. In a trial of rifampin in a dosage of 600 mg daily, the bacterial viability fell to undetectable levels in the first specimen taken after the start of therapy (at 3–4 days in 4 patients, 7–8 days in 9, and 14 days in 2). Dapsone-treated controls required 20 to more than 112 days for the same change. In a trial of a single dose of 1,500 mg rifampin, the viability fell to undetectable levels in the first specimen taken after the start of therapy also (at 3–5 days in all 14 patients).