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February 22, 2011 | Comments: 0

When Grapefruit and Medicine Don’t Mix

Many people taking cardiovascular 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.

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 with grapefruit happens fast and can last 24 hours or longer—the time it takes for your body to make new enzymes. To further complicate things, grapefruit juice can also lower blood levels of a few drugs by reducing absorption. Moreover, the effect can vary from person to person, and even from grapefruit to grapefruit. This makes the scenario highly unpredictable.

Here are some cardiovascular 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).

Grapefruit can also interact with lots of other drugs, including certain tranquilizers and sedatives, antidepressants, drugs for erectile dysfunction, and some forms of estrogen.

Many drugs carry a warning label if they interact with grapefruit. But the absence of a warning doesn’t mean there is no inter­action. If you take any medications, ask your doctor and/or pharmacist about combining them with grapefruit.

Some drug inserts warn of interactions between the drug and large quantities of grapefruit juice. For example, the Merck insert for its cholesterol drug Zocor (simvastatin, now sold also as a generic) specifies more than a quart of juice because nearly all the studies have used such large amounts of (or double-strength) grapefruit juice. Most studies also looked at people drinking some of the juice around the time they took the drugs. It’s safest not to drink even smaller amounts, however.

What you can do

• Switch to other juices. There is some evidence, though, that Seville oranges (which are sour, like grapefruit) may have an effect similar to that of grapefruit. Tangelos, pomelos, cranberries, and pomegranates may also interact with certain drugs.

• Switch to another drug in the same category. This isn’t always possible but your doctor or pharmacist should be able to advise you. 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), rosuvastatin (Crestor), or fluvastatin (Lescol), which are metabolized differently by the body.

• 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. 

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