Grapefruit can have a number of interactions with drugs, often increasing the effective potency of compounds. Grapefruit contains naringin, bergamottin and dihydroxybergamottin, which inhibit the cytochrome P450 isoform CYP3A4 in the intestine. It is via inhibition of this enzyme that grapefruit increases the effects of buspirone (Buspar), carbamazepine, several statin drugs (such as simvastatin), terfenadine, felodipine, nifedipine, verapamil, estradiol, tacrolimus, dextromethorphan (significant only at recreational doses), benzodiazepines, and ciclosporin.[10][11][12][13][14] The effect of grapefruit juice with regard to drug absorption was originally discovered in 1989. However, the effect became well-publicized after being responsible for a number of deaths due to overdosing on medication.
