 Rifampin induces the activity of the phase 2 enzymes glucuronosyltransferase and sulfotransferase. In a PK drug interaction between rifampin and moxifloxacin, the moxifloxacin AUC0-24 decreased 27 ratio of geometric mean, 73 90 CI, 64 to 84 with coadministration of rifampin at a dose of 600 mg daily. In a PK interaction study of 19 participants who had tuberculosis, moxifloxacin AUC0-24 and Cmax decreased when moxifloxacin was administered daily with rifampin and isoniazid compared with moxifloxacin alone ratio of geometric mean AUC0-24, 0.69 90 CI, 0.65 to 0.74; Cmax, 0.68 90 CI, 0.64 to 0.73. With rifapentine dosing 3 times per week in a PK interaction study in healthy volunteers, moxifloxacin AUC0-inf was decreased 17. In the RIFAQUIN PK study with 28 adults who had pulmonary tuberculosis treated with a continuation-phase regimen of 400 mg moxifloxacin and 900 mg rifapentine twice weekly, or 400 mg moxifloxacin and 1200 mg rifapentine once weekly, median moxifloxacin AUC0-inf with rifapentine treatment once weekly was decreased 9 or twice weekly was decreased 11. These PK drug interaction studies indicate that moxifloxacin AUC0-inf is decreased with increased frequency of rifamycin dosing from once weekly up to daily dosing. The magnitude of reduction in moxifloxacin concentrations when it is given with rifapentine at a dose of 1200 mg daily is unknown. 