David Bailey, professor of clinical pharmacology at the University of Western Ontario and leader of the study was the first researcher to identify grapefruit juice can increase the absorption of certain drugs two decades ago, perhaps turning some doses toxic.
Grapefruit, orange and apple juices can harm the body's ability to absorb certain medications and make the drugs less effective, says a Canadian study published last week in the United States.
Research has shown that these juices can decrease the effectiveness of drugs used to treat heart disease, cancer, organ transplant rejection and infection, "potentially wipe out their beneficial effects," he said.
The new results came as part of its continuing research on the subject, and were presented at the 236th annual meeting of the American Chemical Society in Philadelphia, Pennsylvania.
"Recently, we discovered that grapefruit and other fruit juices decrease the oral absorption of certain drugs during the intestinal absorption of transport," AFP quoted Bailey as saying.
"The concern is loss of benefit of medications essential for the treatment of serious diseases."
Healthy volunteers took fexofenadine, an antihistamine used to fight against allergies, or with a glass of grapefruit juice, a glass of water with naringin (which gives the bitter taste of grapefruit juice) or water.
Those who drank the grapefruit juice absorbed only half the amount of fexofenadine, compared with those who drank the water.
Researchers said the water with naringin served to block "a carrier of the absorption of drugs, called OATP1A2 involved in the shuttle drugs from the small intestine into the blood."
Among the drugs affected by consumption of grapefruit, orange juice and apple are: etoposide, an anticancer agent, beta-blockers (atenolol, celiprolol, talinolol) used to treat high blood pressure and prevent heart attacks and certain antibiotics (ciprofloxacin, levofloxacin, itraconazole).
The drug for lowering interaction also affected cyclosporine, a drug taken to prevent rejection of transplanted organs, and more drugs should be added to the list of research pursued.
Bailey said patients should consult a doctor about taking medications with juice, and stick to water while taking most medications.
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