Fig. 1.

Plasma levels of tamoxifen and metabolites before and after rifampin administration. Blood samples were obtained prior to rifampin treatment with baseline collected right before rifampin initiation. Follow-up samples were collected 2 and 10 weeks post-rifampin discontinuation. Plasma concentrations of tamoxifen and endoxifen (a) and primary metabolites, NDM-tamoxifen and 4-OH-tamoxifen (b) were measured from each blood sample. Horizontal shaded region in (a) depicts the sub-therapeutic range. Vertical shaded region in (a) and (b) depicts the time period of rifampin treatment