Fig. 5.
CYP3A4 inhibition by rifampicin (open circles) or rifabutin (filled circles), normalized to untreated control. Metformin (filled squares) was used as an inert non-inhibitor control and ketoconazole (10 µM, filled diamond) as a strong CYP3A4 inhibitor positive control. Data shown are the mean ± SEM of 3 independent replicates with n = 3. The data were fitted to an Emax model (four parameter-logistic equation; variable slope). The data points for metformin were simply connected. Individual EC50 and Emax values are listed in