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More on why compounds in grapefruit interfere with some medications.

Q. I know you shouldn't drink grapefruit juice with certain medications. Is it safe to wait a few hours before taking my pills?

A. No, that won't help. Adverse reactions with certain medications can occur for up to 24 hours after grapefruit or grapefruit juice is consumed.

A little over a decade ago, scientists discovered that grapefruit juice contains a substance that blocks the liver's ability to break down certain drugs, resulting in higher than expected levels of the drug in the body and creating the potential for dangerous side effects. Though less common, it can also reduce blood levels of drugs and possibly reduce their effectiveness. Since then, several natural compounds in grapefruit have been identified that are involved in the food-drug interaction, including the flavonoid naringin and the psoralen furanocoumarin. Seville oranges, used to make some marmalades and limes may contain compounds that have similar interaction.

The compounds in question, however, are not found in most other citrus fruits, including oranges, lemons or tangerines, so these fruits, juices and juice blends are not a potential problem.

The following drugs have been found to interact with grapefruit juice (to be sure of your medications, ask your pharmacist): calcium channel blockers (for high blood pressure)--felodipine (Plendil), nifedipine (Procardia, Adalat), nisoldipine (Sular); immunosuppressant drugs (for organ transplants)--cyclosporine (Neoral, Sandimmune, SangCya), tacrolimus (Prograf); drugs for anxiety, insomnia or depression--diazepam (Valium), triazolam (Halcion), zaleplon (Sonata), carbamazepine (Tegretol), clomipramine (Anafranil).

Statins Also Affected. The most recent discovery is that some statins, a popular class of cholesterol-lowering drugs, also interact with grapefruit. A woman who took the statin Zocor and ate one grapefruit every day for two weeks required hospitalization after experiencing muscle weakness and pain. Doctors linked her condition, rhabdomyolysis, a rare yet serious side effect of statin therapy, to the combination. Other common statins used to treat high cholesterol are lovastatin (Mevacor) and atorvastatin (Lipitor).

Fortunately, most drugs are safe to take with grapefruit or grapefruit juice or any blend containing grapefruit juice. To be sure patients understand which medications are affected, pharmacists are now required to place a sticker on any prescription drug that should not be taken with grapefruit or grapefruit juice.

EN's Bottom Line: If you're taking any of the medications known to interact with grapefruit, or if you're not sure, avoid grapefruit and grapefruit juice completely.

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Title Annotation:Ask EN
Publication:Environmental Nutrition
Geographic Code:1USA
Date:Jun 1, 2004
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