More Health News | Metabolizing medication

Grapefruit reacts with more drugs

Sunday December 30, 2012 8:57 AM

Twenty years ago, Canadian researchers discovered that grapefruit interferes with the body’s metabolism of certain drugs, including the immunosuppressant cyclosporine and at least one drug used to treat high blood pressure.

The same group of scientists reported recently that the number of drugs that react adversely with grapefruit has increased, from 17 to 43. The list includes cholesterol-lowering statins such as Zocor and Lipitor and blood-pressure medications such as Nifediac and Afeditab.


The amount of grapefruit that can set off a reaction varies from drug to drug, the study notes, but in many cases, about 8 ounces of juice or a whole grapefruit “has sufficient potency to cause a pertinent pharmacokinetic interaction.”

The drugs in question have three common traits: They’re all taken orally; they all have limited bioavailability (only small percentages of the active drug make it into the bloodstream); and they all interact in the GI tract with an enzyme called CYP3A4. The researchers have identified more than 85 drugs that might interact with grapefruit, but some of these interactions are unlikely to cause serious adverse effects.