Grapefruit Juice and Drugs

Why many prescription medications include the warning, “do not take with grapefruit juice.”

The reason is because grapefruit juice messes with your body’s ability to properly metabolize the medicine. It blocks a crucial enzyme (CYP3A4) that controls how much of the medicine you receive. Drinking even one glass of grapefruit juice throws off the safe dose. Basically, it is subject to a potentially dramatic increase in systemic exposure and associated higher risk of overdose with grapefruit as a result of diminished the CYP3A4 activity, primarily in the small intestine, rather than in the liver.