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March 5, 2010 | Comments: 4

The Grapefruit Effect and Your Drugs

Many people taking medications have learned to be leery of grapefruit and its juice—which is too bad, since grapefruit is not only delicious, but also heart-healthy and nutritious. Here's what you need to know.

Grapefruit and its juice raise blood levels of certain drugs, and the effect can be dangerous. This occurs because grapefruit contains substances that disable an enzyme (known as CYP3A4) in the small intestine that would otherwise help break down the drugs. The interaction happens fast and can last 24 hours or longer—the time it takes for your body to make new enzymes—though it trails off. On the other hand, grapefruit juice can also lower blood levels of a few drugs by reducing absorption.

These effects can vary from person to person—and even from grapefruit to grapefruit. This makes the scenario highly unpredictable.

The drugs include many cholesterol-lowering statins, as well as certain calcium channel blockers (for high blood pressure), tranquilizers, antihistamines, Antidepressants, and HIV drugs. Many drugs now carry a warning label if there’s an interaction with grapefruit—but the absence of a warning doesn’t mean there is no inter­action. If you take medication and consume grapefruit, check with your doctor or pharmacist.

What you can do

• Switch to other juices. There is some evidence, however, that Seville oranges (which are sour, like grapefruit) may have an effect similar to grapefruit, as may tangelos and pomelos.

• Switch to another drug in the same category. This isn’t always possible—your doctor or pharmacist should be able to advise about this. For example, the blood pressure drug nifedipine (such as Procardia) is affected by grapefruit, but you might take diltiazem (such as Cardizem) instead. Your prescription for Lipitor or Zocor might be changed to rosuvastatin (Crestor), which does not interact with grapefruit or its juice.

• Keep in mind, the main concern is regular consumption of the fruit or its juice. A glass of juice on rare occasion should pose little or no risk—especially if you drink it in the morning, say, and take your drug in the evening. 

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