Bactericidal activities of combinations of new drugs against Mycobacterium leprae in nude mice.

The bactericidal activities of 12 regimens with various combinations of new drugs (clarithromycin [CLARI], minocycline [MINO], and ofloxacin [OFLO]) and the standard antileprosy drugs, especially rifampin (RMP), were compared in nude mice with established Mycobacterium leprae infection. The longest duration of treatment was 24 weeks for intermittent (once every 4 weeks) therapy and 8 weeks for daily therapy. Bactericidal effects were monitored by titrating the proportion of viable M. leprae isolates by subinoculating the organisms into the footpads of immunocompetent and nude mice. The results indicate that RMP was more bactericidal than any combination of the new drugs. A single dose of CLARI-MINO, with or without OFLO, displayed bactericidal activity as great as that of 4 weeks of daily treatment with dapsone (DDS) plus clofazimine (CLO); thus, intermittent CLARI-MINO, with or without OFLO, may replace DDS and CLO of the standard multidrug regimen, and these will become regimens that can be administered monthly and under full supervision. Additional evidence that this may be the case is provided by the finding that intermittent RMP-CLARI-MINO or RMP-CLARI-MINO-OFLO administered for 12 or 24 weeks was as active as the standard multidrug regimen. While the intermittent treatment always displayed significantly greater bactericidal activity than the same number of doses of daily treatment, daily treatment with CLARI-MINO and CLARI-MINO-OFLO were more active than the drugs given as intermittent treatment for the same duration; therefore, unless these combinations are to be administered together with intermittent RMP, they should be given daily, especially for the treatment of RMP-resistant cases of infection. Finally, 12 weeks of daily treatment with DDS-CLO was more bactericidal than had been expected, suggesting that it may not be necessary to administer the standard multidrug regimen for multibacillary leprosy for as long as 24 months in order to minimize the risk of developing RMP resistance.

Clinical trial of ofloxacin alone and in combination with dapsone plus clofazimine for treatment of lepromatous leprosy.

Twenty-four patients with newly diagnosed lepromatous leprosy were allocated randomly to three groups and treated for 56 days with 400 mg of ofloxacin daily, 800 mg of ofloxacin daily, or 400 mg of ofloxacin, 100 mg of dapsone, and 50 mg of clofazimine daily plus 300 mg of clofazimine once every 28 days. The patients in all three groups demonstrated remarkable clinical improvements, accompanied by rapid decline of the morphological index in skin smears during treatment. More than 99, > 99.99, and > 99.99% of the viable Mycobacterium leprae organisms had been killed by 14, 28, and 56 days of treatment, respectively, as measured by inoculation into the footpads of immunocompetent and nude mice of organisms recovered from skin biopsy specimens obtained before and during treatment. Mild to moderate elevations of the serum glutamic pyruvic transaminase level were observed in four patients, all after 28 days of treatment, which returned to normal after the trial had been completed. Clinical improvement, bactericidal activity, and hepatotoxicity did not differ significantly among the three groups. Ofloxacin displayed powerful bactericidal activity against M. leprae in leprosy patients and may be an important component of new multidrug regimens for the treatment of leprosy. Its optimal dosage appears to be 400 mg daily, and combination with dapsone and clofazimine does not enhance its activity.