Grapefruit Juice and Medications May Not Mix
Grapefruit juice can cause serious consequences for people on certain medications, according to a report in the American Journal of Nursing.
"The Grapefruit Challenge: The juice inhibits a crucial enzyme, with possibly fatal consequences," focuses on interactions between grapefruit juice and medications, which have long been recognized.
The US Food and Drug Administration requires all prospective new medications 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, Amy Karch, R.N., M.S., of the School of Nursing at the University of Rochester Medical Center, says many healthcare professionals and patients do not know about the risk.
"The potential of drug interactions with grapefruit juice has been out there a long time, but most people just aren't aware of it," says Karch.
"There is so much information bombarding people all the time, that a lot of people may have heard this but forgotten it," she says. "But the problems can be life-threatening."
Karch 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.
The patient profiled in Karch's article had high cholesterol and other risk factors for cardiac disease. The physician put the patient on atorvastatin (Lipitor®), and the patient began dieting and exercising.
Two months after the patient went to Florida for the winter, he suddenly had muscle pain, fatigue, and fever, and went to the emergency room.
The only major change in the person's lifestyle had been that, upon arriving in Florida, he began picking grapefruit off a tree on the patio and drinking two or three glasses of fresh grapefruit juice every day.
Karch, an expert on medication 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 medications.
The cytochrome P-450 3A4 enzyme breaks down grapefruit juice into useful components for the 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.
Medications that use the same pathway and interact with grapefruit juice target some of the most common health problems physicians see today. The list consists of more than 50 medications, including some 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.
However, she says that many patients fail to read the warning labels about medication-food interactions.
The consequences of an interaction depend on the medication 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 antidepressant 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 will not 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 rhythm might become irregular if an antiarrhythmia medication cannot 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.
To prevent such problems, Karch repeats what physicians and nurses tell their patients every day: Read a medication's warning label carefully. If an interaction with grapefruit juice is possible, the patient should stop drinking the juice until speaking with his or her physician.
In some cases it might be possible to switch an individual to a different medication without the risk; in other cases the person might simply have to give up grapefruit juice.
She says that more people than usual are vulnerable at this time of year, because losing weight is among the most popular New Year's resolutions, and some diets are built around drinking lots of grapefruit juice.
Always consult your physician for more information.
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