Harvard Health Letter

Should you avoid grapefruit juice?

Switching to another medication may keep juice on the menu.

Drinking grapefruit juice may interfere with some prescription medications. But you may not have to avoid the juice. "It's much less of a problem than you've heard. And in most instances you can drink it," says Dr. Bruce Bistrian, chief of clinical nutrition at Beth Israel Deaconess Medical Center and a professor at Harvard Medical School.

The problem

The drugs in many pills that you swallow get broken down in your intestines by an enzyme called CYP3A before they enter your bloodstream. That breakdown reduces the absorption of certain drugs. But grapefruit juice contains compounds called furanocoumarins that stop CYP3A from doing its job. As a result, more of the drug is absorbed, making it more powerful than it's meant to be, even toxic in some cases.

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