Drug–Grapefruit Juice Interactions

We have summarized the clinical findings on druggrapefruit juice interactions

Garvan C. Kane

2009

Scholarcy highlights

  • Grapefruit juice, a beverage consumed in large quantities by the general population, is an inhibitor of the intestinal cytochrome P-450 3A4 system, which is responsible for the first-pass metabolism of many medications
  • Purchased by 21% of all households in the United States, grapefruit juice carries the American Heart Association's healthy "heart-check" food mark and contains compounds that may both reduce atherosclerotic plaque formation' and inhibit cancer cell proliferation. 3,4 unlike other citrus fruit juice, grapefruit juice interacts with a variety of prescription medications, raising the potential for concern. This is worrying in that juice and medications are commonly consumed together at breakfast. This drug-food interaction seems to occur through inhibition by grapefruit juice of one of the intestinal cytochrome P-450 enzyme systems, cytochrome P-450 3A4
  • CYF3A4 substrates) has been reported.v-" there are no published data, one can assume that grapefruit juice would increase sildenafillevels if it were concurrently administered. This would improve efficacy as well as increase the incidence of adverse effects, eg, headache, flushing, dyspepsia, and vision changes, albeit in a variable manner. What does all this discussion mean for the practicing physician? The American public is consuming grapefruit juice in greater quantities,' with 14% of men drinking the juice at least weekly." One can expect that, with the recent fortification of citrus juices with calcium, the intake of both orange juice and grapefruit juice will increase, in middle-aged and elderly populations, groups in which the intake of medications is highest
  • There is an increased awareness of this potential for drug-food interaction in the clinical pharmacology and drug regulatory communities, drug-grapefruit juice interactions may be underappreciated by general physicians
  • We have summarized the clinical findings on druggrapefruit juice interactions
  • No specific studies have addressed the adverse effects of drug-grapefruit juice interactions
  • There are no published case reports of adverse effects due to such interactions, we must assume they do occur

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