Grapefruit juice has been extensively studied for its ability to interact with drugs. As a naturally occurring product, the interacting substance(s), not fully identified, appear in different quantities in different fruit. The commercial juicing process forces large quantities of potentially interacting substances normally present in the pith and rind into juice. This has lead to the suggestion that the whole grapefruit is less likely to interact as the fruit juice.
Furanocoumarins have been identified as ingredients in grapefruit juice that inhibit intestinal cytochrome P450 isoenzyme CYP3A4, meaning that there may be increased plasma concentrations of the substrates of CYP3A4 during consumption of the juice. The interaction of grapefruit juice with statins is of interest, due to the common use of these drugs, sometimes as primary prevention in currently healthy people.
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A joint initiative of the Patient Services Section and the Drug and Therapeutics Information Service of the Pharmacy Department, Repatriation General Hospital, Daw Park, South Australia. The RGH Pharmacy E-Bulletin is distributed in electronic format on a weekly basis, and aims to present concise, factual information on issues of current interest in therapeutics, drug safety and cost-effective use of medications.
Editor: Assoc. Prof. Chris Alderman, University of South Australia – Director of Pharmacy, RGH © Pharmacy Department, Repatriation General Hospital, Daw Park, South Australia 5041.