Love grapefruit?

It might not love you back

Created date

January 24th, 2020
Grapefruits, like the ones seen here, may not mix well with your medications.

Grapefruits, like the ones seen here, may not mix well with your medications.

Ah…grapefruit! Love it or hate it, this fruit is high in vitamin C, potassium, and fiber. But taking your morning meds after a breakfast of grapefruit, or washing them down with grapefruit juice, can be harmful. According to the U.S. Food and Drug Administration (FDA), grapefruit can have a negative effect on more than 50 prescription and over-the-counter drugs. 

Drugs work too well or not well enough

The main problem with most drugs that interact with grapefruit is that too much drug ends up in your bloodstream. “When there is too much drug in the blood, you may have more side effects,” says Shiew-Mei Huang, Ph.D., a pharmacist with the FDA.

Beyond side effects, high drug levels can be very harmful to tissues and organs. For example, drinking grapefruit juice while taking certain statin drugs can greatly increase your risk for liver and muscle damage, which can eventually lead to kidney failure. 

Here’s how it happens: Many drugs are broken down (metabolized) in the small intestine by an enzyme called CYP3A4. Grapefruit prevents this enzyme from working, and, as a result, too much medication ends up in your bloodstream. 

Scientists have known about this problem with grapefruit for a long time. But according to Huang, more recent studies have found that it can have an opposite effect with some other drugs. 

“For a drug to work properly, it must make its way into your body’s cells,” Huang explains. “Proteins called transporters help that process along, but grapefruit interferes with transporters and, thus, less drug gets into your bloodstream and the drug might not work as well.

There is no way to predict how grapefruit juice will affect you. That’s because everyone has different amounts of CYP3A4 in their intestines, and the enzyme’s actions may vary. Transporters and their actions also vary from person to person.

If you think maybe a little bit won’t hurt, think again. Studies show that as little as two wedges of grapefruit or one cup of juice can be enough to disrupt your medications.

Know in advance

According to the FDA, warning labels are required for prescription and over-the-counter drugs that interact with grapefruit. You can also ask your health care provider or pharmacist, read the medication guide that comes with prescription drugs, and read the drug facts label or other warnings on the bottle or medication packaging.

Finding grapefruit or its juice in other foods and beverages might take a little detective work. It can sneak into other combination products, such as mixed-fruit juices or items flavored with fruit juice. Read the ingredients lists very carefully. 

A solution on the horizon

The problems with grapefruit and medicine hasn’t escaped the notice of the research community. Some scientists are developing types of grapefruits that will be safe to mix with medications. They are not yet available, though, so you still need to ask your primary care doctor about any food restrictions on your current regimen. 

Did you know? Seville oranges (also called bitter oranges, sour oranges, or marmalade oranges), pomelos, and tangelos have a similar effect on medications as grapefruit. Source: National Institutes of Health

A few examples

Some drugs that can interact with grapefruit:

• Nifedipine, for high blood pressure

• Cyclosporine, to prevent organ transplant rejection

• Buspirone, for anxiety

• Budesonide, for Crohn’s disease or ulcerative colitis

• Amiodarone, for abnormal heart rhythm

Please note: Grapefruit juice does not affect all drugs in any particular class or category. In addition, the severity of in interaction can be different depending on the person, the drug, and the amount of grapefruit juice ingested. To be absolutely safe, talk to your doctor, pharmacist, or other health care provider and also read any information provided with your prescription or over-the-counter drugs.