The number of medications that interact with grapefruit, with potentially serious results, is on the rise, new research finds.


They found that between 2008 and 2012, about six new medications whose interactions with grapefruit can cause serious damage came to market each year, bringing the number from 17 to 43. (Altogether, more than 85 drugs that might interact with grapefruit exist, but some such interactions aren’t likely to cause serious adverse effects.)

Chemicals in grapefruit called furanocoumarins change the way these medications are metabolized in the gastrointestinal tract, dramatically increasing concentrations of the drug in the bloodstream. Those chemicals are also present in other citrus fruits such as Seville oranges – the kind often used to make marmalade – and limes and pomelos, the study notes, but not in oranges.

The drugs in question have three common traits: They’re all taken orally, they all have limited bioavailability (meaning only small percentages of the active drug make it into the bloodstream under normal circumstances) and they all interact in the GI tract with an enzyme called CYP3A4. That information is available on drug package inserts, the study notes, but many people, including physicians, may not be aware of its importance.

The list of such drugs includes commonly used cholesterol-lowering statins such as Zocor and Lipitor and blood-pressure medications such as Nifediac and Afeditab, the study notes.

Those high concentrations of drugs in the body can be toxic to the kidneys and can also lead to GI-tract bleeding, respiratory failure, bone-marrow suppression (among people with comprised immune systems)  -- and even sudden death.

These interactions can take place many hours after grapefruit (or grapefruit juice) is consumed, and even just a single grapefruit or glass of grapefruit juice a day can spell trouble if you’re taking one of these drugs..

Those of us older than 45 are at increased risk, in part because, the study notes, we buy more grapefruit than younger people do and also have more prescription drugs in our lives. Older people are more susceptible to the ill effects of high concentrations of drugs in their system, too, the study says.

This all means that it’s a good idea to ask your physician or pharmacist about the prescription drugs you take and whether they’re likely to be affected by grapefruit consumption.