Grapefruit and medicines: Can they mix?
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The bottom line
At least 85 drugs are thought to interact with grapefruit. Grapefruit can cause those drugs to be poorly absorbed or to stay in your system much longer than usual. As a result, the drug may not work because the blood concentrations are too low, or more toxic effects may be seen because of abnormally high blood concentrations.
Prevention tips
Tell your physician and pharmacist if you consume grapefruit.
Look at your prescription medicine bottle. If there's a sticker warning you about grapefruit, don't eat or drink any grapefruit products.
Ask your pharmacist to double-check if it is safe to take grapefruit with your medicine.
This really happened
Case 1: A 52-year-old man was taking sertraline and bupropion for depression. One day, he drank a large amount of grapefruit juice. The following day, he developed a severe headache. He called his poison center because of his symptoms. There is a known drug interaction between sertraline and grapefruit juice; when they are taken together, there is an increased risk of side effects or toxicity from the sertraline. The man was advised to discontinue his sertraline for a few days. After doing so, his headache resolved.
Case 2: A 50-year-old woman was taking amlodipine, atenolol, and clonidine for high blood pressure. She drank about 6–8 ounces of grapefruit juice with every meal for 2 days. On the third day, she began experiencing lightheadedness, dizziness, and nausea. The grapefruit juice was interacting with her amlodipine, which made her blood pressure drop too low. Her poison center recommended that she stop drinking the grapefruit juice. She followed the poison center's directions, and her symptoms resolved in 3 days.
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Does grapefruit interfere with prescription drugs?
Experts have known for years that it's not safe to mix grapefruit and some prescription drugs. At least 85 drugs are known or suspected to interact with grapefruit (see the table listed in the For More Information section, below). Many of them can cause serious effects. These include dangerous heart rhythms, kidney damage, muscle damage, respiratory depression, and bleeding from the stomach or intestines.
Other fruits can have similar effects but too a lesser extent than is seen with grapefruit. Some examples include oranges, grapes, apples, mangos, and papaya. Interactions with these fruits are possible but uncommon.
How do the interactions work?
Drug interactions can occur with grapefruit, grapefruit juice, or even grapefruit marmalade. There are 2 types of potential interactions between drugs and grapefruit.
The first results in decreased absorption of some drugs from the gastrointestinal tract. This causes lower drug concentrations in the blood, resulting in less effect of the drug. One of the best-known examples of this effect is grapefruit’s interference with the absorption of levothyroxine, the most common drug for treating hypothyroidism (low thyroid).
In the second—and more dangerous—type of interaction, grapefruit can inactivate an enzyme that metabolizes many drugs. This can result in much higher blood concentrations of the drugs and increases the risk of toxicity. Because grapefruit permanently prevents the enzyme from breaking down the drugs, the body must manufacture more enzyme molecules. This can take 36 hours or more. For that reason, staggering the timing of medicines and grapefruit has a limited effect.
The effect of grapefruit on drug metabolism depends on the amount of grapefruit consumed. More grapefruit means more effect. People who consume large amounts of grapefruit (more than 1 liter of juice per day) are at the greatest risk of experiencing adverse effects.
Signs and symptoms of a grapefruit interaction
The most well-known example of a grapefruit interaction is muscle damage caused by some statins. These are drugs used to treat high cholesterol. Atorvastatin (Lipitor), lovastatin (Mevacor), and simvastatin (Zocor) are known to interact with grapefruit. In one report, a single glass of grapefruit juice every day for 3 days caused the blood concentration of simvastatin (Zocor) to increase more than 300 percent. The muscle damage results in muscle pain and tenderness. The breakdown products from damaged muscles can also injure the kidneys.
Erythromycin, a common antibiotic, can cause a dangerous heart rhythm if taken with grapefruit. Nifedipine (Procardia), taken for high blood pressure, can interact with grapefruit to cause very low blood pressure. Hallucinations and seizures can result from combining dextromethorphan, a cough suppressant, with grapefruit.
At least 10 cancer chemotherapy drugs can interact with grapefruit. In these cases, the risk is a dangerous, irregular heart rhythm (torsade de pointes), as well as muscle damage. Some of these cancer drugs are everolimus, dasatinib, and vemurafenib. Other types of drugs that interact with grapefruit include some pain relievers, sedatives, and drugs for prostate enlargement.
Are my drugs safe to take with grapefruit?
When a prescription is filled, the label usually states whether you should avoid any particular foods, so always read your prescription labels carefully and completely. Make sure that your physician and pharmacist are aware of your grapefruit consumption.
If you take a drug that interacts with grapefruit—and you really love grapefruit—there might be a workaround. Sometimes, another drug that has the same action can be substituted. Check with your physician to see if that might be possible for you.
Concerned about a drug interaction with grapefruit?
If you have questions about medicine interactions, use the webPOISONCONTROL® online tool to get help, or call your poison center at 1-800-222-1222. Whether online or by phone, expert guidance is always free, confidential, and available 24 hours a day.
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