We conducted a phenotyping cocktail study in participants with pulmonary TB to assess the effect of optimized, high-dose rifampicin (40 mg/kg/day; RIF40), as compared to a standard dose of 10 mg/kg/day (RIF10), on the activity of five major cytochrome P450 (CYP) enzymes [CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4/5 (CYP3A)] and P-glycoprotein (P-gp). This evidence concerns the gene CYP3A4 and pulmonary tuberculosis.