1 hydroxymidazolam

8′-hydroxyefavirenz, efavirenz-d4, losartan, losartan-carboxylic acid (E3174), losartan-d4, omeprazole, 5′-hydroxyomeprazole, omeprazole-d3, metoprolol, α-hydroxymetoprolol, and metoprolol-d7 were purchased from TRC (Toronto, Canada). 1′-hydroxyMidazolam and Midazolam-d6 were acquired from Lipomed (Arlesheim, Switzerland), whereas rifampicin and β-glucuronidase (type HP-2 from Helix pomatia) were obtained from Sigma-Aldrich (Sigma- Aldrich Chemie GmbH, Buchs, Switzerland). Midazolam (F. Hoffmann-La Roche, Basel, Switzerland) and efavirenz (Merck, NJ, USA) were kindly provided by the respective manufacturers. The chemical structures of the probe drugs and their phase I metabolites are provided in Supplementary Figure 2. Formic acid, HPLC grade methanol, and HPLC grade water were purchased from Merck (Darmstadt, Germany). Media used were purchased from GIBCO (Lucerne, Switzerland).
Stock solutions, calibration, and quality control spiking solutions were prepared in DMSO. Calibration standards and quality controls were prepared by enriching the respective medium with the corresponding spiking solutions. Internal standard solutions containing the deuterated cocktail probe drugs were prepared in methanol.