HealthDay News — There are increasing numbers of newly marketed drugs that have the potential to interact with grapefruit, all of which are metabolized by the cytochrome P450 3A4 enzyme (CYP3A4), according to a recent review.

“The number of drugs on the market with the potential to produce serious adverse and in many cases life-threatening effects when combined with grapefruit has markedly increased over the past few years from 17 to 43 in four years,” David G. Bailey, Ph.D., from the Lawson Health Research Institute in London, Canada, and colleagues reported in CMAJ, the journal of the Canadian Medical Association.

Consuming grapefruit or grapefruit juice with certain medications can cause serious side effects, including sudden death, acute kidney failure, respiratory failure and gastrointestinal bleeding. And many health care providers may not be aware of these dangerous interactions.

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Bailey and colleagues conducted a systematic review of the literature, mainly randomized controlled trials, to examine the scientific concepts and clinical implications of the grapefruit-drug interaction.

More than 85 drugs may interact with grapefruit, 43 of which have interactions that can trigger serious adverse effects, the researchers found. Characteristics of medications that interact with grapefruit include: oral administration; very low-to-intermediate absolute bioavailability; and all are metabolized by CYP3A4. In the gastrointestinal tract, grapefruit and certain related citrus fruits can irreversibly inhibit CYP3A4.

So consuming even a small amount of grapefruit hours before taking a medication, can increase the amount of the drug metabolized, which is like taking many doses at once, the researchers explained.

Older patients are the most vulnerable to adverse clinical effects due to grapefruit-medication interactions, as  people older than 45 years are the major demographic for purchasing grapefruit and are more likely than younger people to take a variety of medications.

Drugs identified that interact with grapefruit include:

  • Certain statins — Zocor (simvastatin), Lipitor (atorvastatin) and Pravachol (pravastatin)
  • Some BP-lowering drugs — nifedipine (Nifediac and Afeditab)
  • Organ transplant rejection drugs — cyclosporine (Sandimmune and Neoral)
  • Certain cardiovascular drugs — amiodarone (Cordarone and Nexterone), clopidogrel and apixaban

“The current trend of increasing numbers of newly marketed grapefruit-affected drugs possessing substantial adverse clinical effects necessitates an understanding of this interaction and the application of this knowledge for the safe and effective use of drugs in general practice,” the researchers wrote.


  1. Bailey DG et al. CMAJ. 2012; doi:10.1503/cmaj.120951.