Rifampin in the treatment of leprosy.

The minimal inhibitory concentration of rifampin for Mycobacterium leprae is less than 1 microgram/ml. Therapy with rifampin has proved efficacious both in mice experimentally infected with M. leprae and in humans with leprosy. Rifampin kills M. leprae more rapidly than do other antileprosy drugs currently available. Consequently, M. leprae bacilli from patients with lepromatous disease are rendered noninfectious within three weeks after the institution of rifampin therapy, as determined in the mouse footpad test system. Administration of this antibiotic substantially reduces the quantities of M. leprae discharged in the nasal secretions of lepromatous patients within three weeks, thus rapidly decreasing the potential infectivity of these individuals. Intermittent rifampin therapy for leprosy has been successful, with a low incidence of adverse reactions to the drug. Worldwide, the prevalence of primary and secondary resistance of M. leprae to dapsone has increased markedly. Therefore, the World Health Organization recommends a multidrug regimen that includes intermittent administration of rifampin for the treatment of leprosy.