FDA Issues Warning of Grapefruit, Drug Interaction

FDA has published information on its Consumer Update website about potential negative interactions between grapefruit juice and fresh grapefruit and prescription drugs. While acknowledging that grapefruit can be part of a healthy diet, offering nutrients like vitamin C and potassium, and that grapefruit juice does not interact with all drugs, the agency does explain that grapefruit juice can interfere with the action of some prescription and nonprescription drugs.

FDA says that some prescription drugs are required to carry a warning against consuming fresh grapefruit or grapefruit juice while taking the drug, and that “the agency’s current research into drug and grapefruit juice interaction may result in label changes for other drugs as well.”

In the Consumer Update, the agency explains that grapefruit juice can sometimes increase-or in other cases, lessen-the absorption of certain drugs. As an example, the agency said that certain substances in grapefruit juice may block the action of CYP3A4, an enzyme that breaks down a drug in the small intestine so that it can be metabolized. As a result, more of the drug may stay in the body, increasing risk of adverse events such as liver damage and muscle breakdown, which can lead to kidney failure. The agency said that certain cholesterol-lowering statin drugs, blood pressure-lowering drugs, organ transparent rejection drugs, anti-anxiety drugs, and antihistamines may react with grapefruit juice in this way-even if the juice is consumed several hours before or after medication is taken.

Conversely, grapefruit juice can sometimes inhibit the body’s absorption of certain drugs, such as seasonal allergy medication fexofenadine, by blocking the action of transporters that help transport a drug into cells to be absorbed.

FDA also pointed out that grapefruit juice interacts differently with different drugs and in different people. It advises consumers consult their physicians for advice.