Fruit Juice and Pharmaceuticals Collide

We reported on this site long ago that grapefruit juice is known to boost the absorption of certain medications. You'll find your doctor has plenty to say about taking these drugs along with grapefruit juice, and the pharmacist will also pass along a stern warning.

But now it turns out that grapefruit juice isn't the only juice that doesn't mix well with drugs. The Canadian researcher who first identified the ill effects of grapefruit juice has gone on to publish new science that shows a few other fruit juices have the same problem.

Orange and apple juice, two of the most common fruit juices in today's refrigerator, may limit the body's absorption of drugs and compromise their effectiveness. Dr. David Bailey, a professor of medicine and pharmacology at the University of Western Ontario presented his research recently at the American Chemical Society's national meeting, in Philadelphia.

"The original finding is that [grapefruit juice] markedly boosts the amount of drug that gets into the bloodstream," Bailey said. He first reported that nearly 20 years ago when he discovered that grapefruit juice increased the body's blood levels of felodipine (Plendil), used to treat high blood pressure. Since the original finding, other researchers have identified dozens of other medications that could interact adversely with grapefruit juice.

The American Academy of Family Physicians says that doctors traditionally warn against drinking grapefruit juice if you're taking certain medications for high cholesterol, high blood pressure and heart rhythm problems.

In his latest research, Bailey found that grapefruit juice, as well as orange and apple juice, can lower the body's absorption of some medications. Those drugs include the anti-cancer drugs etoposide (Etopophos, Vepesid); certain beta blockers like tenormin (Atenolol) and talinolol (Cordanum), used to treat high blood pressure and prevent heart attacks; cyclosporine, which is used to prevent organ transplant rejection; and some antibiotics, including ciprofloxacin (Cipro), levofloxacin (Levaquin), and itraconazole (Sporanox).

Bailey also found that healthy volunteers who took the allergy drug fexofenadine (Allegra) with grapefruit juice absorbed only half the amount of the drug, compared with volunteers who took the medicine with water.

In each case, substances in the juices affected the absorption of the drugs. Some chemicals block a drug uptake transporter, reducing drug absorption; other chemicals block a drug metabolizing enzyme that normally breaks down the drugs.

Dave