February 2013

If you’re taking any regular medications, check with your doctor before including grapefruit or grapefruit juice in your diet. That’s the takeaway from a new review of the evidence on grapefruit-drug interactions, which concluded that the number of drugs that react adversely with grapefruit is higher than previously thought. Scientists identified more than 85 common drugs, including those for infections, cholesterol and gastrointestinal disorders, that interact with grapefruit. Nearly half were associated with potentially serious adverse events. Common effects of grapefruit interactions range from dizziness and urinary retention to loss of drug effectiveness and gastrointestinal bleeding. Grapefruit juice also caused drug interactions at lower levels than previously suspected—as little as seven or eight ounces. Writing in CMAJ, David Bailey, PhD, of the London (Ontario) Health Sciences Center, and colleagues noted, "Unless healthcare professionals are aware of the possibility that the adverse event they are seeing might have an origin in the recent addition of grapefruit to the patient’s diet, it is very unlikely that they will investigate it."