Some fruit juices, like grapefruit juice, orange juice, and apple juice, may impair the body’s ability to absorb certain medications and decrease the effectiveness of drugs, a Canadian study finds.
The research showed that these juices can reduce the effectiveness of certain drugs used to treat cancer, heart disease, and infection.
“Recently, we discovered that grapefruit and these other fruit juices substantially decrease the oral absorption of certain drugs undergoing intestinal uptake transport,” said study leader David Bailey, a professor of clinical pharmacology with the University of Western Ontario in London, Ontario.
In the study, healthy volunteers were given fexofenadine, an antihistamine used to treat allergies. The subjects consumed the drug with either a glass of grapefruit juice, a glass of water containing naringin, or a glass of plain water.
The results showed that those who drank the grapefruit juice and water with naringin absorbed only half the amount of fexofenadine, compared to those who drank plain water.
“Loosing half of the amount of drugs taken into the body can be critical for the performance certain drugs,” Bailey said.
According to the researchers, naringin (substance in grapefruit that gives the juice its bitter taste) appears to block a key drug uptake transporter called OATP1A2, involved in shuttling drugs from the small intestine to the bloodstream.
“Blocking this transporter reduces drug absorption and neutralizes their potential benefits. By contrast, drugs whose levels are boosted in the presence of grapefruit juice appear to block an important drug metabolizing enzyme, called CYP3A4, that normally breaks down drugs,” the researchers said.
In addition to grapefruit juice, apple juice and orange juice also appear to contain naringin-like substances that inhibit OATP1A2. “The chemical in oranges appears to be hesperidin, but the chemical in apples has not yet been identified,” the researchers notes.
So far, among the drugs affected by the consumption of grapefruit, orange and apple juices are etoposide, a type of anti-cancer drug; beta blockers (atenolol, celiprolol, talinolol); and certain antibiotics (ciprofloxacin, levofloxacin, itraconazole).
The drug-lowering interaction also affected cyclosporine, a drug taken to prevent rejection of transplanted organs, and more drugs were expected to be added to the list as the research continued.
“This is just the tip of the iceberg,” Bailey said. “I’m sure we’ll find more and more drugs that are affected this way.”
Bailey advises patients to consult with their doctor before taking any medications with grapefruit juice or other fruits juices. He recommends taking most medications with plain water.
