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Should you avoid grapefruit juice?

Switching to another medication may keep juice on the menu.

Drinking grapefruit juice may interfere with some prescription medications. But you may not have to avoid the juice. “It’s much less of a problem than you’ve heard. And in most instances you can drink it,” says Dr. Bruce Bistrian, chief of clinical nutrition at Beth Israel Deaconess Medical Center and a professor at Harvard Medical School.

The problem

The drugs in many pills that you swallow get broken down in your intestines by an enzyme called CYP3A before they enter your bloodstream. That breakdown reduces the absorption of certain drugs. But grapefruit juice contains compounds called furanocoumarins that stop CYP3A from doing its job. As a result, more of the drug is absorbed, making it more powerful than it’s meant to be, even toxic in some cases.

The drugs affected most by grapefruit juice include cholesterol-lowering drugs called statins, blood pressure drugs called calcium-channel blockers, and anti-anxiety medications.

Different drugs in the same class may be more or less affected by grapefruit. This table lists the generic and brand names of drugs that are more or less affected.

DRUG CLASS

BIG EFFECT

LITTLE OR NO EFFECT

Benzodiazepines
(anxiety, insomnia)

diazapam (Valium)
midazolam (Versed)
triazolam (Halcion)

clonazepam (Klonapin)
flurezapam (Dalmane)

Calcium-channel blockers (high blood pressure, angina)

felodipine (Plendil)
nifedipine (Procardia, Adalat)

amlodipine (Norvasc)
diltiazem (Cardizem)
verapamil (Calan, Isoptin)

Statins (cholesterol)

atorvastatin (Lipitor)
lovastatin (Mevacor)
simvastatin (Zocor)

fluvastatin (Lescol)
pitavastatin (Livalo)
pravastatin (Pravachol)
rosuvastatin (Crestor)

The good news

Not all drugs in a class—such as statins—are affected by grapefruit juice. So simply switching to another type within that class may enable you to enjoy a drink of the juice.

Photo: Thinkstock

If you can’t switch to another brand, your doctor may still give you a green light to enjoy grapefruit juice. Why? “Most of the research on grapefruit juice interactions has been in test tubes, which doesn’t translate well to people,” says Dr. Bistrian. “And many studies used massive amounts of furanocoumarins, found in a quart or more of grapefruit juice. The amount in an 8-ounce glass of grapefruit juice would be clinically insignificant in most cases,” he says. Your risk is even lower if you eat a half grapefruit, since it takes several fruit to produce a single glass of juice.

What you should do

Talk to your doctor about whether the fruit or juice will interact with your medication, and if there’s another type of medication you can take to avoid an interaction (see table at left). You must also ask how often you can have grapefruit, since the effect of furanocoumarins can last for three days. Even if you do get the okay, avoid drinking grapefruit juice with your medications.

Posted by: Dr.Health

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