Early bactericidal activity of a moxifloxacin and isoniazid combination in smear-positive pulmonary tuberculosis

Abstract

Background: In vitro and animal studies have shown that moxifloxacin-containing combinations may improve the bactericidal efficacy of antituberculosis regimens. Patients and methods: We measured the decline in the sputum viable count of 13 patients who were given a combination of moxifloxacin 400 mg daily and isoniazid 300 mg daily. Results: The time required to reduce the viable count by 50% (vt₅₀) was 0.38 days (95% CI −0.03–0.78 days, SEM 0.13) and the mean early bactericidal activity (EBA) was 0.60 log₁₀ cfu/day (95% CI 0.23–0.97, SEM 0.14). This compares with the vt₅₀ calculated for isoniazid and moxifloxacin alone in the same population of 0.48 and 0.88 days, respectively. The EBA values for isoniazid and moxifloxacin alone were 0.77 and 0.53 log₁₀ cfu/day, respectively. Conclusions: The combination of moxifloxacin and isoniazid is not antagonistic, but the combination does not significantly enhance bactericidal activity above that of isoniazid alone.