Grapefruit juice and medication do not mix well

27/01/05 Grapefruit juice can be deadly for people on certain medications, nurse researchers remind doctors, nurses, and everyone who takes medicine and enjoys grapefruit juice, in a paper in the American Journal of Nursing, a journal of the American Nurses Association.

Amy Karch, R.N., M.S., of the School of Nursing at the University of Rochester Medical Center reported on a man from a northern climate who moved to Florida for the winter - one of tens of thousands of "snowbirds" who head south each winter - and began drinking two to three glasses of grapefruit juice each day. Two months later the man died, the victim of a deadly interaction between grapefruit juice and his cholesterol-lowering medication.

Interactions between grapefruit juice and medications have long been recognized. Last year, the Medical Letter on Drugs and Therapeutics devoted an entire issue to grapefruit juice and the dangerous drug interactions that can result. The U.S. Food & Drug Administration requires all prospective new drugs to be tested for interactions with grapefruit juice. And a warning about grapefruit juice is included in the "food-drug interactions" that come with dozens of medications. Nevertheless, Karch says many health-care professionals and patients don`t know about the risk.

Karch, an expert on drug interactions, explains that grapefruit juice is one of the foods most likely to cause problems with drugs, because it is metabolized by the same enzyme in the liver that breaks down many drugs. The cytochrome P-450 3A4 enzyme breaks down grapefruit juice into useful components for body, just like it breaks down dozens of medications. Karch says when the system is overloaded, the grapefruit juice can "swamp" the system, keeping the liver busy and blocking it from breaking down drugs and other substances.

Drugs that use the same pathway and interact with grapefruit juice target some of the most common health problems doctors see today. The list consists of more than 50 medications, including some drugs used to treat high cholesterol, depression, high blood pressure, cancer, depression, pain, impotence, and allergies.

Karch notes that interactions with grapefruit juice are well known and documented among drug researchers, and that an appropriate warning label is included with each prescription. Nevertheless, she says that many patients, nurses and doctors aren`t aware of the interactions or the potential serious consequences, and that many people fail to read the warning labels about drug-food interactions.

The consequences of an interaction depend on the drug involved. A woman on birth-control pills who drinks a lot of grapefruit juice might find herself pregnant because the juice blocks the action of the medication. A person on an anti-depressant might have too much or too little energy, depending on the specific medication. Someone on antibiotics might end up with diarrhea or could be ill longer than usual because the drug won`t work as well as it should. A heart patient might not get the lowered blood pressure that a medication should deliver, or the heart`s rhythms might become irregular if an anti-arrhythmia drug can`t do its job.

The most severe effects are likely with some cholesterol-lowering medications, Karch says. While the liver devotes its resources to grapefruit juice, the medication can build up to dangerous levels, causing a breakdown of the body`s muscles and even kidney failure. This is what happened to the patient discussed in the article.

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