Fruit juice restricts drug absorption

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By Communications Staff
Wednesday, August 20, 2008
A University of Western Ontario professor says drinking fruit juice while taking certain drugs decreases absorption and potentially wipes out its beneficial effects.
 
David Bailey, professor of clinical pharmacology at Western and study leader, suggests common fruit juice like grapefruit, apple and orange can have adverse effects on certain drugs, including some prescribed for fighting life-threatening conditions, such as heart disease, cancer, organ-transplant rejection, and infection.
 
The study was presented Tuesday at the 236th National Meeting of the American Chemical Society in Philadelphia, Pa.
 
"This is just the tip of the iceberg," says Bailey. "I'm sure we'll find more and more drugs that are affected this way."
 
Bailey and fellow Lawson Health Research Institute scientists Richard Kim and George Dresser found only half of fexofenadine, an antihistamine used to fight allergies, was absorbed when taken with grapefruit juice compared to taking the drug with water alone.
 
"Recently, we discovered that grapefruit and these other fruit juices substantially decrease the oral absorption of certain drugs undergoing intestinal uptake transport," says Bailey. "The concern is loss of benefit of medications essential for the treatment of serious medical conditions."
 
Loosing half of the amount of drugs taken into the body can be critical for the performance certain drugs, he adds.
 
They also found grapefruit juice blocked a key drug uptake transporter involved in shuttling drugs from the small intestine to the bloodstream, reducing drug absorption and neutralizing its potential benefits.
 
However, drugs whose levels are boosted in the presence of grapefruit juice appear to block an important drug metabolizing enzyme.
 
Almost 20 years ago, Bailey and colleagues announced grapefruit juice can dramatically boost the body's levels of the high-blood-pressure drug felodipine, causing potentially dangerous drug concentrations in the blood.
 
Since then, other researchers have identified nearly 50 medications that show a similar "Grapefruit Juice Effect.”
 
Certain antibiotics, high blood pressure drugs, beta blockers and anti-cancer agents have made the list of drugs affected by fruit juices. Some currently have warning labels against taking grapefruit juice or fresh grapefruit during drug consumption.

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