More Juices Found to Affect Drugs' Effectiveness: Study (HealthDay)

TUESDAY, Aug. 19 (HealthDay News) -- Grapefruit juice, long knownto boost the absorption of certain medications, isn't the only juice thatdoesn't mix well with drugs, according to the Canadian researcher whofirst identified the ill effects of grapefruit juice.

Other common juices, including orange and apple, may limit the body'sabsorption of drugs, compromising their effectiveness, said David Bailey,a professor of medicine and pharmacology at the University of WesternOntario, in London, Ontario, Canada.

Bailey was expected to present his research Tuesday at the AmericanChemical Society's national meeting, in Philadelphia.

"The original finding is that [grapefruit juice] markedly boosts theamount of drug that gets into the bloodstream," Bailey said. He firstreported that nearly 20 years ago when he discovered that grapefruit juiceincreased the body's blood levels of the drop felodipine (Plendil), usedto treat high blood pressure.

Since the original finding, other researchers have identified dozens ofother medications that could interact adversely with grapefruit juice,Bailey said.

Doctors traditionally warn against drinking grapefruit juice if you'retaking certain medications for high cholesterol, high blood pressure andheart rhythm problems, according to the American Academy of FamilyPhysicians.

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

Bailey also found that healthy volunteers who took the allergy drugfexofenadine (Allegra) with grapefruit juice absorbed only half the amountof the drug, compared with volunteers who took the medicine withwater.

In each case, substances in the juices affected the absorption of thedrugs. Some chemicals block a drug uptake transporter, reducing drugabsorption; other chemicals block a drug metabolizing enzyme that normallybreaks down the drugs, he said.

"We don't [yet] know all the drugs affected," Bailey said.

Michael Gaunt is a medication safety analyst at the Institute for SafeMedication Practices in Horsham, Pa. He said, "If this study holds true[in future research], you are going to have to warn people in a similarfashion" about other juices.

Gaunt's advice for now: "In general, it's safest to take medicationwith water."

Bailey agreed. If you opt for water, he said, "a glass is better than asip. It helps dissolve the tablet." And cool water is better than hot, headded, because your stomach empties cool water faster, sending themedication on its way to the small intestine and finally the bloodstream.

More information

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