[Activity of rifampicin administered daily and intermittently on experimental tuberculosis in mice]

Intermittent regimens with rifampicin (RMP) for chemotherapy of pulmonary tuberculosis are cheaper and can be usually supervised more easily than daily regimens. They are recommended, specially, in developing countries. The present study is designed to evaluate the reduction of RMP activity as the interval between doses is increased in experimental mouse tuberculosis. The mice are given 10 mg/kg oral doses of RMP once, twice, three times or six times a week. The RMP activity is measured as the decrease of viable counts (cfu) in the spleen of mice. RMP given once a week has no activity neither in combination with isoniazid and streptomycin on a large population of organisms nor alone on a small population. RMP given alone twice a week has an activity slightly better than RMP given once a week. RMP given alone three times a week has a weak but not worthy activity: the mean number of cfu after a three times weekly treatment is significantly lower than the mean number of cfu in control (p less than 0.001) but significantly higher than the mean number of cfu after a six times weekly treatment (p less than 0.001). These experimental results are consistent with the experimental data on the effects of RMP on the RNA polymerase. They are not favourable to the intermittent administration of RMP in the chemotherapy of tuberculosis.