Grapefruit and Medicine

Orange You Glad, May 2009

Many people taking medications have learned to be leery of grapefruit and its juice—a wise but most unwelcome development for them, since grapefruit is not only delicious, but also heart-healthy and nutritious.

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. 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.

Here are a few drugs that don’t mix with grapefruit:
• Some cholesterol-lowering statin drugs, including lovastatin (brand name Mevacor), atorvastatin (Lipitor), and simvastatin (Zocor).
• High blood pressure drugs such as the calcium channel blocker nifedipine (such as Procardia or Adalat).
• Heart drugs such as amiodarone (Cordarone or Pacerone).
• Tranquilizers and sedatives such as diazepam (Valium), triazolam (Halcion), buspirone (BuSpar), and zaleplon (Sonata).
• Antidepressants such as sertraline (Zoloft).
• Antihistamines such as fexofenadine (Allegra).
• Some forms of estrogen.
• Some protease inhibitors for HIV, notably saquinavir (Fortovase).
• Drugs for erectile dysfunction such as sildenafil (Viagra) and vardenafil (Levitra).

If you take any medications, ask your doctor and/or pharmacist about combining them with grapefruit. The list above does not include all drugs or even all categories. 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.

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 that of grapefruit. And tangelos, pomelos, cranberries, and pomegranates may also interact with certain drugs.
• 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 pravastatin (Pravachol), which does not interact with grapefruit or its juice.
• Some experts suggest waiting 72 hours after you drink grapefruit juice or eat grapefruit before taking one of the affected drugs, but obviously this won’t work for medication taken daily.

UC Berkeley Wellness Letter, April 2007

Your Health and Mine