Grapefruit–drug interactions

Some fruit juices and fruits can interact with numerous drugs, in many cases causing adverse effects. The effect is most studied with grapefruit and grapefruit juice, but similar effects have been observed with certain other citrus fruits.

One whole grapefruit, or a small glass (200 mL, 6.8 US fl oz) of grapefruit juice, can cause drug overdose toxicity. Fruit consumed three days before the medicine can still have an effect. The relative risks of different types of citrus fruit have not been systematically studied. Affected drugs typically have an auxiliary label saying "Do not take with grapefruit" on the container, and the interaction is elaborated upon in the package insert. People are advised to ask their physician or pharmacist about drug interactions. However, some experts believe that for the majority of patients, complete avoidance of grapefruit is unwarranted.

Although a prospective cohort study of middle-aged women indicated that some flavonoid-rich foods are associated with a reduction in all-cause mortality, frequent grapefruit consumption was associated with a small increase in all-cause mortality, possibly because of the clinically significant drug interactions of the non-flavonoid components.