Grapefruit Juice Greatly Reduces the Plasma Concentrations of the OATP2B1 and CYP3A4 Substrate Aliskiren

In a randomized crossover study, 11 healthy volunteers ingested 200 ml of grapefruit juice or water three times a day for 5 days. On day 3, they ingested a single 150-mg dose of aliskiren. Grapefruit juice reduced aliskiren peak plasma concentration (C-max) by 81% (range, 42-91%, P < 0.001), area under the plasma aliskiren concentration-time curve (AUC)(0-infinity) by 61% (range, 15-72%, P < 0.001), and elimination half-life (t(1/2)) from 26.1 to 23.6 h (P = 0.020). Therefore, concomitant use of aliskiren and grapefruit juice is best avoided.