WARNING!! Grapefruit Juice does not mix well with some drugs, says FDA

While grapefruit juice is healthy for the body as it is rich in vitamin C, it may interfere with the action of some drugs, stated the apex drug regulatory body the US Food and Drug Administration (FDA) in its recent consumer update.

In this consumer update, Shiew Mei Huang, Ph.D., of the U.S. Food and Drug Administration, stated that this food and drug interaction can be a concern and the FDA has required that some prescription and over-the-counter (OTC) drugs taken by mouth include warnings against drinking grapefruit juice or eating grapefruit while taking the drug.

The update placed a few examples of drugs that may cause problems when mixed with grapefruit.

• Some statin drugs to lower cholesterol, such as Zocor (simvastatin) and Lipitor (atorvastatin).


• Some drugs that treat high blood pressure, such as Procardia and Adalat CC (both nifedipine).


• Some organ-transplant rejection drugs, such as Sandimmune and Neoral (both cyclosporine).


• Some anti-anxiety drugs, such as buspirone.


• Some corticosteroids that treat Crohn's disease or ulcerative colitis, such as Entocort EC and Uceris (both budesonide).


• Some drugs that treat abnormal heart rhythms, such as Pacerone and Nexterone (both amiodarone).


• Some antihistamines, such as Allegra (fexofenadine).

The update also mentioned that the interaction of grapefruit juice may vary with the person, drug and amount of juice consumed, and may not be critical in all cases of drugs mentioned above.

The update has advised patients to talk to the doctor, pharmacists or other healthcare provider and read any information provided with the prescription or OTC drug to find out the following

• If your specific drug may be affected.


• How much, if any, grapefruit juice one can have.


• What other fruits or juices may also affect the drug in a similar way to grapefruit juice.

How Grapefruit Juice Can Interfere With Medications

With most drugs that interact with grapefruit juice, "the juice lets more of the drug enter the blood," Huang says. "When there is too much drug in the blood, you may have more side effects."

For example, if you drink a lot of grapefruit juice while taking certain statin drugs to lower cholesterol, too much of the drug may stay in your body, increasing your risk for liver and muscle damage that can lead to kidney failure.

Many drugs are broken down (metabolized) with the help of a vital enzyme called CYP3A4 in the small intestine. Grapefruit juice can block the action of CYP3A4, so instead of being metabolized, more of the drug enters the blood and stays in the body longer. The result: too much drug in your body.

The amount of the CYP3A4 enzyme in the intestine varies from person to person, says Huang. Some people have a lot of enzymes and others just a little. So grapefruit juice may affect people differently even when they take the same drug.

Although scientists have known for several decades that grapefruit juice can cause too much of certain drugs in the body, Huang says more recent studies have found that the juice has the opposite effect on a few other drugs.

"Grapefruit juice can cause less fexofenadine to enter the blood," decreasing how well the drug works, Huang says. Fexofenadine (brand name Allegra) is available as both prescription and OTC to relieve symptoms of seasonal allergies. Fexofenadine may also not work as well if taken with orange or apple juice, so the drug label states "do not take with fruit juices."

Why this opposite effect? Instead of changing metabolism, grapefruit juice can affect proteins in the body known as drug transporters, which help move a drug into our cells for absorption. As a result, less of the drug enters the blood and the drug may not work as well, Huang says.