What is in grapefruit that makes it interact with medicines?

Answer 1

A daily glass of grapefruit juice or half of a grapefruit for breakfast is normally considered a healthy diet choice: that grapefruit delivers vitamin C, fiber, and potassium. However, grapefruit can be dangerous if taken along with certain of the statin class of cholesterol-lowering prescription medicines.

Grapefruit and grapefruit juice interact with multiple prescription medicines, and consuming grapefruit while on these medications can be dangerous. In fact, there are many medications that interact with grapefruit, including the cholesterol-lowering statins Zocor (simvastatin), Lipitor (atorvastatin) and Pravachol (pravastatin).

Which Medications Interact With Grapefruit?

Grapefruit should be avoided (or minimized - best bet is to discuss with your doctor) when taking a surprisingly broad group of medicines. According to the FDA's Grapefruit Juice and Medicine May Not Mix, grapefruit can interfere with certain of the cholesterol-lowering statins as listed above, some blood-pressure medications, some antihistamines, as well as other drug classes.

How Does Grapefruit Interact With Prescription Medicines?

Essentially, the juice of grapefruit changes the absorption of certain drugs into the bloodstream. Katherine Zeratsky, a Mayo Clinic Nutritionist, explains, "Problems arise because chemicals in the fruit can interfere with the enzymes that break down (metabolize) the medication in your digestive system. As a result, the medication may stay in your body for too short or too long a time. A medication that's broken down too quickly won't have time to work. On the other hand, a medication that stays in the body too long can increase to potentially dangerous levels, causing serious side effects." For statins in particular, grapefruit juice increases the level of statin in the blood, to a potentially dangerous level.

What If I Take My Prescription Hours After Eating Grapefruit?

Though eating grapefruit or drinking grapefruit juice hours before or after taking a prescription medicine seems a good strategy, it is not. Shiew Mei Huang, acting director of the Food and Drug Administration's Office of Clinical Pharmacology, explains, "Drinking grapefruit juice several hours before or several hours after you take your medicine may still be dangerous, so it's best to avoid or limit consuming grapefruit juice or fresh grapefruit when taking certain drugs.

Conclusion

For those not on prescription medication of any sort, grapefruit and grapefruit juice are a terrific nutritional choice. But if you take any prescription medication - especially statins to lower cholesterol - you should avoid grapefruit and grapefruit juice, or at least discuss with your doctor.

Did You Know?

Grapefruit juice decreases the effectiveness of allergy medications like Allegra (fexofenadine) by inhibiting the absorption of the drug itself. It may be less effective with apple and Orange Juice as well, so the fexofenadine label states "do not take with fruit juices."