Why can't you take prescription medications with grapefruit?

Why can't you take prescription medications with grapefruit?
Grapefruit is a good source of vitamin C and the antioxidant lycopene. But the citrus fruit also contains chemicals that interfere with the enzymes that normally break down drugs in your digestive system. When those enzymes fail to do their job, the drug enters your bloodstream at higher-than-acceptable levels, increasing your risk of developing side effects.


Until last year, scientists blamed the flavonoids found in grapefruit as the source of interference. But a study published last May in the American Journal of Clinical Nutrition discovered that a group of natural chemicals called furanocoumarins were the likely culprit. The study compared the effects of orange juice, regular grapefruit juice, and furanocoumarin-free grapefruit juice on 18 people taking Plendil, a drug used to treat high blood pressure. Blood levels of Plendil were higher when the drug was taken with regular grapefruit juice, but not with orange juice or furanocoumarin-free juice.


Grapefruit most commonly interacts with drugs taken for high blood pressure, high cholesterol, depression, anxiety, allergies, HIV, impotence, and seizures. If you're taking medication for any of these conditions, avoid grapefruit as a snack or juice. To be on the safe side, also stay away from tangelos, which are a hybrid of tangerine and grapefruit.


-Gina L. Nick, N.M.D., Ph.D., medical director at Serenity Wellness Center (serenitywellnessctr.com) in Costa Mesa, Calif.


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