Grapefruit Counteracts Drugs -- MEDICA - World Forum for Medicine

Grapefruit Counteracts Drugs

Foto: Carafe and glas with juice and grapefruits aside

Drinking grapefruit juice with
certain drugs could lower their
effectiveness; © Florida
Department of Citrus

These findings show that grapefruits and other fruits as apples and oranges can wipe out beneficial effects of drugs by substantially decreasing the absorption. The study provides a new reason to avoid drinking grapefruit juice and these other juices when taking certain drugs, including some that are prescribed for fighting life-threatening conditions such as heart disease, cancer, organ-transplant rejection, and infection, the researcher says.

Scientists announced almost 20 years ago the finding that grapefruit juice can boost the body's levels of the high-blood-pressure drug felodipine, causing potentially dangerous effects from excessive drug concentrations in the blood. Since then, nearly 50 medications were identified that carry the risk of grapefruit-induced drug-overdose interactions. As a result of the so-called "Grapefruit Juice Effect," some prescription drugs now carry warning labels.

In the new research, the scientists had healthy volunteers take fexofenadine, an antihistamine used to fight allergies. The volunteers consumed the drug with either a single glass of grapefruit juice, water containing only naringin (substance in grapefruit juice that gives the juice its bitter taste), or water. When fexofenadine was taken with grapefruit juice, only half of the drug was absorbed compared to taking the drug with water alone.

They also showed that the active ingredient of grapefruit juice, naringin, 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 neutralises their potential benefits, the researchers say.

Orange and apple juices 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 note.; Source: American Chemical Society