 Autoinduction has been described previously with daily dosing of rifamycins, including rifampin and rifapentine. With autoinduction of metabolizing enzymes or transporters, both bioavailability and clearance can theoretically be affected. In a population PK model from healthy volunteers, rifapentine clearance appeared to be time-dependent, whereas time had a less significant effect on bioavailability. In addition, there was no clear relationship between dose and clearance, or dose and the effects of time on clearance. Further in this prior study, the time to maximal autoinduction with daily dosing could not be estimated as increases in clearance were seen up until the final PK sampling day after 14 days of dosing. PK sampling over longer dosing intervals is required to determine the time course of autoinduction and the change in exposures over time with repeated dosing. 