Proximal Roux-en-Y gastric bypass alters drug absorption pattern but not systemic exposure of CYP3A4 and P-glycoprotein substrates.

Study Objectives: To evaluate the effect of Roux-en-Y gastric bypass surgery (RYGB) on the pharmacokinetics of midazolam (a CYP3A4 substrate) and digoxin (a P-glycoprotein substrate).

Design: Prospective, nonblinded, longitudinal, single-dose pharmacokinetic study in three phases: presurgery baseline and postoperative assessments at 3 and 12 months.

Patients: Twelve obese patients meeting current standards for bariatric surgery.