The fact that grapefruit juice raises the bioavailability of many drugs has been attributed to the irreversible inhibition of intestinal CYP3A4 and P-gp, in view of the fact that intravenously tered drugs are not affected. A large number of flavonoid studies have revealed in vitro pharmacokinetic interference. How ever, the main inhibitory effect on intestinal CYP3A4 and P-gp is attributed to some furanocoumarins and bergamottin, and the inhibition of OATP1A2 to naringin, which together could lead to some clinically important pharmacokinetic alterations.