Drug Interactions of Grapefruit and Other Citrus—What Have We Learned?

The first report of grapefruit juice (GFJ) interacting with a drug, altering its bioavailability, was published in 1991. This accidental discovery was made in a study on ethanol-drug interactions-the bioavailability of felodipine was increased when subjects were consuming GFJ concomitantly with felodipine, associated with a lower dehydrofelodipine/felodipine area under the curve (AUC) ratio, decreased diastolic blood pressure, and an increased heart rate (1). Subsequent research in the area of fruit-drug interactions focused on grapefruit and grapefruit compounds of which several were found to affect the absorption or metabolism of certain drugs. GFJ was shown to alter the pharmacokinetics of several drugs such as statins, calcium channel blockers, antibiotics, and others (1-8). Other fruits, vegetables, and dietary supplements also have the potential to cause an adverse interaction with conventional drugs (9). Over 16% of all prescription drug users reported that they concurrently use at least one plant-based dietary supplement, including grapefruit and citrus products (10).