Cohen Medical Associates is a family medical center and research center located in Delray Beach, FL.
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The Potential Dangers With Grapefruit

Your primary care doctors in Delray Beach, Florida, at Cohen Medical Associates, always encourage our patients to consume healthy foods as much as possible: lean meats, nuts, vegetables, and fruits. This includes fruit juices like grapefruit juice in place of sodas.

The problem with grapefruit and grapefruit juice, however, is that it can interfere with important medications. Grapefruit isn’t the only fruit juice that can have this effect, by the way. Marmalade made from Seville oranges can have a similar effect, as can limes, pomelos, and tangelos, along with citrus-flavored soft drinks which may contain grapefruit.

So why would something that is otherwise healthy for you have such potentially dangerous consequences?

The U.S. Food and Drug Administration (FDA) explains that certain compounds contained in grapefruit interfere with the way many medications are metabolized.

With most drugs that interact with grapefruit juice, “the juice lets more of the drug enter the blood,” says the FDA’s Shiew Mei Huang, PhD. “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, according to the FDA.
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 FDA warns.

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 years that grapefruit juice can cause too much of the drug to enter the patient’s bloodstream, it’s only recently that research has shown it can have the opposite effect on some drugs.

For example, grapefruit juice can prevent the drug fexofenadine (Allegra) from entering the blood.

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, the FDA’s Huang says.

Since it’s often difficult to achieve the proper potency when introducing a new drug to a patient, the introduction of a foreign agent such as grapefruit juice into the mix can complicate an already delicate process. Not only that, when mixed with some drugs, grapefruit and the other fruits noted above can be deadly.

A drug concentration that is too high can cause such harmful effects as respiratory failure, kidney damage, intestinal-tract bleeding, even death. Those with compromised immune systems may experience bone-marrow suppression.

Studies have found nearly 100 medications that can be affected by consumption of grapefruit and other citrus fruits and juices. The FDA provides some examples: some statins; some high-blood pressure medications; some anti-anxiety drugs; some corticosteroids; some drugs that treat abnormal heart rhythms; and some organ-transplant rejection drugs such as cyclosporine.

By the way, with some of these drugs, even taking the drug and the fruit or juice at different times of the day may not be enough. Any time you consume some of the troublesome fruits or juices while on certain medications will have an effect.

What can you do to make sure this doesn’t happen to you? Check with your primary care doctors at the time we write your script. Check with the pharmacist when you pick up your medication. And be sure to read all the interactions and warnings on the package insert which is included with any drug dispensed in the U.S., even if you think you know all there is to know about your prescription. The improvement of your condition—or even your life—may depend on it.

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