Update: Grapefruit Juice-Drug Interactions Still Pose Risks

Nursing journal sends out renewed warning on potentially dangerous consequences

FRIDAY, Jan. 21, 2005 (HealthDayNews) -- American nurses are getting a reminder that grapefruit juice is notable for more than its ability to make you pucker: In some cases, it can spell big trouble for people who take certain prescription drugs.

Grapefruit juice can interfere with the body's absorption of some two dozen medications, from the cholesterol-lowering drug Lipitor to erectile-enhancing Viagra. While warnings appear in the information given to patients, they're easy to miss, said Amy Karch, a clinical associate professor of nursing at the University of Rochester Medical Center who wrote an article warning about the risks in last month's issue of the American Journal of Nursing.

"A lot of people rely on their health-care providers to alert them to anything that would be really important, but it is so hard to keep up with all of the constantly changing drug information that there probably are doctors who are not aware of the possibility," Karch said.

But don't rush to throw out your carton of grapefruit juice just yet. The fruit itself has gained a reputation as a possible fat-fighter, and one doctor speaking for fruit growers said patients shouldn't overreact when they hear about potential drug interactions.

The risks of grapefruit juice are not new, but many patients don't seem to be aware of it, Karch said.

According to researchers, grapefruit juice affects the production of enzymes in the liver, which is part of the body's filtration system. The liver also metabolizes drugs and, in some cases, the presence of grapefruit juice can boost or diminish the concentration of a drug in the body, strengthening or weakening its effects.

For example, it's conceivable that grapefruit juice could boost the effectiveness of a blood pressure-lowering medication, said Dr. Ken Fujioka, director of nutrition and metabolic research at Scripps Clinic in San Diego. "If you're driving blood pressure too low, patients can get into problems -- they can get lightheaded and pass out."

In her article, Karch tells the story of a 59-year-old retired government auditor who had several risk factors for heart disease, including obesity and high cholesterol. His doctor put him on Lipitor. Meanwhile, the man traveled to his winter home in Florida, and began drinking several glasses of fresh grapefruit juice a day.

The man developed serious kidney problems, and a nurse realized the grapefruit juice may have caused them by boosting the levels of Lipitor in his system. The patient was told to try other medications.

A long list of popular drugs interact with grapefruit juice, including AIDS medications, the blood thinner Coumadin (warfarin), the antibiotic erythromycin, and the hormones estrogen and testosterone.

"The effect is not just immediate, it may last five, six, seven or 12 hours," Fujioka said. "You may have some differences in terms of where the juice is reconstituted, frozen or fresh. There could be huge variations in the effect it has on drug levels."

The good news is that most drugs don't appear to interact with grapefruit juice, and there are often alternatives to those that do, said Dr. Hartmut Derendorf, a professor at the University of Florida's College of Pharmacy, in a statement provided by the Florida Department of Citrus.

And grapefruit itself may have its own health benefits. Fujioka reported last year that people who ate one-and-a-half grapefruit a day lost more weight than those who consumed grapefruit juice, grapefruit extract or a placebo. "It may reasonable to be looking at grapefruit itself as a better alternative" to the juice, he said.

More information

Columbia University has more about potential grapefruit juice interactions.

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