Taking pills? Avoid the juice
Canwest News Service
Tuesday, August 19, 2008
CREDIT: Adam Rountree/Bloomberg
Bailey says people should avoid drinking juices for at least two hours when taking pills, the time it takes most drugs to be absorbed.
The Canadian researcher behind the stickers on prescription drug vials that warn "do not to take with grapefruit or grapefruit juice" now says people should also avoid taking their pills with orange and apple juice.
David Bailey and colleagues announced to a startled, and skeptical medical world nearly 20 years ago that grapefruit juice can dramatically boost the amount of certain drugs absorbed into the bloodstream, turning normal doses into potentially toxic overdoses. Today, 48 medications carry the grapefruit warning.
Now Bailey is reporting that grapefruit juice - as well as orange and apple juice - can do the opposite by substantially decreasing the absorption of other drugs, including certain antibiotics and beta blockers, pills widely prescribed for high blood pressure, congestive heart failure, abnormal heart beats and chest pain.
"When we use drugs, you have to use it at the right dose. Too low a dose doesn't give you the effect you want, too high a dose has the chance of producing too much of an effect or just basic toxicity," says Bailey, a professor of clinical pharmacology at the University of Western Ontario in London.
"It's a window you try and stay within. In the first case we were worried about getting too much in. Now, we're worried about not getting enough in."
"If you're talking about substances that you have to have because of critical medical conditions, like cancer, or if you have had a kidney or some kind of transplant, or if you've had a previous heart attack, you have to get enough into the bloodstream to produce an effect."
People often take medications with juice. But drugs are nearly always tested with water, Bailey says. "So if you want to get the most chance of having the most consistent, uniform effect, what you should really do is take your medication with a whole glass of water on an empty stomach."
He says people should avoid drinking juices for at least two hours, the time it takes most drugs to be absorbed.
In research presented Tuesday at the American Chemical Society's national meeting in Philadelphia, Bailey and colleagues found that when healthy volunteers took fexofenadine, an antihistamine for allergies, with grapefruit juice, only half the drug was absorbed compared to taking the drug with water alone.
"We had expected that the (drug) levels were going to go up. In actual fact they went down. That was a bit of a surprise to us," says Bailey.
The researchers say naringin, the major ingredient that gives grapefruit its distinctive smell and bitter taste, appears to block proteins that ferry drugs from the gut to the bloodstream.
But they were also startled to find orange juice - "common orange juice, which is probably drunk a lot more than grapefruit juice," Bailey says - did the same thing. So did apple juice. Orange and apple juices appear to contain naringin-like substances.
So far, grapefruit, orange and apple juices have been found to lower the absorption of etoposide, an anti-cancer drug; the beta blockers atenolol, celiprolol and talinolol; cyclosporine, a drug used to prevent organ transplant rejection and the antibiotics ciprofloxacin, levofloxacin and itraconazole.
"But I'm sure we'll find many other drugs for which this happens," says Bailey.
In the beginning, no one believed that constituents in food could boost the absorption of drugs. After reporting in 1991 that grapefruit juice boosted the levels of a drug used for high blood pressure three-fold, "we had a hard time convincing people it really did exist. The idea that food could produce this kind of effect was totally novel," Bailey says.
"We were kidded about it because grapefruit seems to be a humorous fruit, and most people didn't know what to think."
The research was eventually published in the Lancet, "because they had confidence this was true," and is now in every medical textbook. Bailey also edits a section of the Compendium of Pharmaceuticals and Specialties, the manual for drug information and safety. "There are almost 50 drugs we have now listed, and that's only the ones that we know about."
Thanks Barry & Louise D.