Grapefruit juice and the actual grapefruit can be part of a healthy diet. Grapefruit has vitamin C and potassium—nutrients your body needs to work properly. But it isn’t good for you when it affects the way your medicines work, especially if you have high blood pressure or arrhythmia (irregular or abnormal heart beat).

Depending on the active ingredient, grapefruit can reduce the effectiveness of a drug or worse, create potentially dangerous drug levels in the body. Grapefruit can interfere with transporters in the intestine that help absorb drugs. When this happens, less of the drug reaches the bloodstream and the patient receives no benefit.

Grapefruit can also interfere with enzymes that break down drugs in your digestive system. This can result in the body absorbing too much of the drug, which can potentially cause serious problems.

Sometimes the juice ain’t worth the squeeze…especially when combining grapefruit with medicines.

While it can be part of a balanced and nutritious diet, grapefruit can have serious consequences when taken with certain medications. Currently, there are more than fifty prescription and over-the-counter drugs known to the U.S. Food and Drug Administration that can have negative interactions with grapefruit.

As little as one cup of juice or two grapefruit wedges can alter the way your medicines work. When taken with medicine, grapefruit can delay, decrease, or enhance absorption of certain drugs; as a result, the patient does not receive the prescribed dosage of the medication. If the label on your medicine reads “DO NOT TAKE WITH GRAPEFRUIT” or has similar words, heed the warning. It can save you a bushel of problems.

How it does or doesn’t work

Depending on the active ingredient, grapefruit can reduce the effectiveness of a drug or worse, create potentially dangerous drug levels in the body. Grapefruit can interfere with transporters in the intestine that help absorb drugs. When this happens, less of the drug reaches the bloodstream and the patient receives no benefit.

Grapefruit can also interfere with enzymes that break down drugs in your digestive system. This can result in the body absorbing too much of the drug, which can potentially cause serious problems.

Help may be on the way

Scientists are currently working on breeding hybrid grapefruits that will be safe to mix with medications. In the near future you may be able to enjoy these tasty mounds without compromising your safety. But until the new fruit containers start to arrive, follow these tips:

• Ask your pharmacist or other health care professional if you can have fresh grapefruit or grapefruit juice while using your medication. If you can’t, you may want to ask if you can have other juices with the medicine.
• Read the Medication Guide or patient information sheet that comes with your prescription medicine to see if it interacts with grapefruit juice. Some information may advise not to take the drug with grapefruit juice. If it’s OK to have grapefruit juice, there will be no mention of it in the guide or information sheet.
• Read the Drug Facts label on your non-prescription medicine, which will let you know if you can have grapefruit or other fruit juices with it.
• If you can’t have grapefruit juice with your medicine, check the label of bottles of fruit juice or drinks flavored with fruit juice to make sure they don’t contain grapefruit juice.
• Seville oranges (often used to make orange marmalade) and tangelos (a cross between tangerines and grapefruit) affect the same enzyme as grapefruit juice, so avoid these fruits as well if your medicine interacts with grapefruit juice.

This document discusses important information to know when you are taking any of the following drugs:

• Amiodarone (Cordarone®, Pacerone®)
• Nifedipine (Procardia®, Aldalat®)
• Buspirone (Buspar®)
• Simvastatin (Zocor®)
• Carbamazepine (Tegretol®)
• Sirolimus (Rapamune®)
• Cyclosporine (Gengraf®, Neoral®)
• Tacrolimus (Prograf®)
• Lovastatin (Mevacor®)

Eating and drinking some citrus fruits and juices and other ingredients can interact with drugs, such as the ones listed above. Intravenous (IV) versions of these drugs do not interact with food.

When taking any of these drugs by mouth, avoid eating and drinking:

• Grapefruit juice

• Fresh, canned, or frozen grapefruit
• Tangelos and pomelos
• Products that contain grapefruit, bitter orange, or Seville orange

Check labels of juices, juice blends, fruit drinks, marinades, marmalades, and sodas for these ingredients.

What is a drug-nutrient interaction?

A drug-nutrient interaction can occur when the food you eat affects how your medicine works. The effect of the medicine may be changed, or there may be serious side effects.

The fruits and ingredients listed above contain chemical compounds that can affect how some medicines are absorbed from the gastrointestinal tract. The absorption of some drugs can be increased or decreased so that the amount of drug in your body is not right.

Do other citrus fruits cause the same problem?

Other citrus fruits, such as lemons, tangerines, and sweet oranges (Blood, Clementine, Mandarin, and Naval) do not cause a problem when taken with these drugs.

What will happen if I accidentally eat grapefruit or any other ingredient listed above?

It is unlikely that accidentally eating or drinking a small amount of these products one time will cause serious problems. These ingredients can affect drug absorption for several days, however. Consult your doctor or pharmacist if you think that you are experiencing side effects.

What if I have always taken my medication with grapefruit?

It is recommended that you stop eating grapefruit. Tell your pharmacist and doctor that you have made this change.

What is the possibility that grapefruit and/or these other ingredients affect other drugs that I take?

While studies are still ongoing, it has been found that these ingredients may change the absorption of several prescription and over-the-counter drugs. Check with your pharmacist about other medications and/or any supplements that you are taking. There may be a drug- nutrient interaction.

Grapefruit juice and the actual grapefruit can be part of a healthy diet. Grapefruit has vitamin C and potassium—nutrients your body needs to work properly.

But it isn’t good for you when it affects the way your medicines work, especially if you have high blood pressure or arrhythmia (irregular or abnormal heart beat).

This food and drug interaction can be a concern, says Shiew Mei Huang, PhD, of the U.S. Food and Drug Administration. 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, Huang says.

Here are examples of some types of drugs that grapefruit juice can cause problems with (interact):

• 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).

Grapefruit juice does not affect all the drugs in the categories above. The severity of the interaction can be different depending on the person, the drug, and the amount of grapefruit juice you drink. Talk to your doctor, pharmacist or other health care provider and read any information provided with your prescription or OTC drug to find out:

• If your specific drug may be affected.
• How much, if any, grapefruit juice you can have.
• What other fruits or juices may also affect your 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.

How Grapefruit Juice Affects Some Drugs

When drugs are swallowed, they may be broken down (metabolized) by enzymes and/or absorbed using transporters in cells found in the small intestine. Grapefruit juice can cause problems with these enzymes and transporters, causing too much or too little drug in the body.

Some drugs, like statins used to lower cholesterol, are broken down by enzymes. As shown above, grapefruit juice can block the action of these enzymes, increasing the amount of drug in the body and may cause more side effects.

Other drugs, like Allegra (fexofenadine) used to treat allergies, are moved by transporters into the body’s cells. As shown above, grapefruit juice can block the action of transporters, decreasing the amount of drug in the body and may cause the drug to not work as well.

Find Out if You Should Avoid Grapefruit or Other Juices

• Ask your doctor, pharmacist or other health care provider if you can drink grapefruit juice while taking your medication.
• Read the medication guide or patient information sheet that comes with your prescription drug to find out if grapefruit juice affects your drug.
• Read the Drug Facts label on your OTC drug, which will say whether you shouldn’t have grapefruit or other fruit juices with it.
• If you must avoid grapefruit juice with your medicine, check the labels of fruit juices or drinks flavored with fruit juice to see whether they are made with grapefruit juice.
• Seville oranges (often used to make orange marmalade), pomelos, and tangelos (a cross between tangerines and grapefruit) may have the same effect as grapefruit juice. Do not eat those fruits if your medicine interacts with grapefruit juice.

What is grapefruit?

Grapefruit is a fruit in the citrus family. Grapefruit and fruits similar to grapefruit, such as Seville oranges, pomelos, and limes, are known to interact with anticancer drugs. The seeds from the fruit contain furanocoumarin that may cause adverse effects.

How is grapefruit given or taken?

People eat grapefruit or take it as a dietary supplement (in the form of an extract made from the seeds). Some people drink grapefruit juice.

Have any studies been done on grapefruit and drug interactions in people with cancer?

A small randomized trial found that less of the anticancer drug etoposide reached the bloodstream in people who drank grapefruit juice than it did in people who did not drink grapefruit juice. However, studies with the anticancer drugs imatinib, sunitinib, and nilotinib have shown that drinking grapefruit juice increased the amount of anticancer drug that reached the bloodstream.

Have any side effects or risks been reported from grapefruit?

Grapefruit can interact with many medicines used to treat a variety of health problems. Grapefruit juice and the furanocoumarin in grapefruit seeds have been known to interact with some anticancer drugs.

Is grapefruit approved by the U.S. Food and Drug Administration (FDA) for use as a cancer treatment in the United States?

FDA has not approved the use of grapefruit as a treatment for cancer or any other medical condition.

Grapefruit is available in the United States in food products or as a dietary supplement. FDA does not approve dietary supplements as safe or effective. The company that makes the dietary supplements is responsible for making sure that they are safe and that the claims on the label are true and do not mislead the consumer. The way that supplements are made is not regulated by FDA, so all batches and brands of grapefruit seed extracts may not be the same.