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From OncoLog, February 2014, Vol. 59, No. 2

House Call: Avoiding Food–Drug Interactions
Some foods and medicines don’t mix

Did you know that what you eat can affect the way your medicine works? Some foods, beverages, vitamins, and supplements can interact with your medicines. These interactions may limit the benefits of your medicines, cause side effects, or lead to a serious health condition. Here, we present some common food-drug interactions and provide tips to help you avoid them.

Foods that interact with medicine

Alcohol. If you take antihistamines or antidepressants—including mood-altering drugs called monoamine oxidase inhibitors, or MAOIs—avoid drinking alcohol because the combination can cause extreme drowsiness. Limit alcohol use when taking medicines that can cause liver damage, such as acetaminophen, aspirin, and ibuprofen. Some cancer medicines can also interact with alcohol, leading to liver damage or vomiting.

Caffeine. Some asthma medicines, such as albuterol and theophylline, can interact with caffeine, leading to excitability and a rapid heart rate.

Fruit. Grapefruit juice can increase the speed at which the body absorbs some medicines, and it may interfere with how the body processes other medicines. These interactions could lead to unwanted health effects. Speak with a pharmacist or doctor before eating grapefruit or drinking grapefruit juice when taking antidepressants or statins (a class of drugs used to treat high cholesterol). Some cancer medicines can also interact with grapefruit juice. Grapefruit, apple, or orange juice may reduce the effectiveness of fexofenadine (an antihistamine).

If you take blood thinners such as heparin and warfarin, ask your health care provider if you should avoid cranberry juice and cranberry supplements, which some reports indicate can reduce the benefits of these medicines or increase the risk of bleeding.

Vitamins and supplements. Garlic, ginseng, and ginkgo should also be avoided when taking blood thinners because these foods increase the chances of bleeding. Other vitamins and supplements can decrease the effectiveness of some medicines. For example, St. John’s wort is an herbal supplement that reduces the benefits of many prescription drugs, including digoxin (used to treat abnormal heart rhythms) and imatinib (used to treat leukemia).

Potassium. If you take medicines for high blood pressure, such as captopril and lisinopril, avoid eating large amounts of foods high in potassium, such as bananas and sweet potatoes. Excessive consumption of these foods when taking these medicines can cause a temporary increase in potassium levels, which may lead to heart palpitations and abnormal heart rhythms.

Tips for avoiding interactions

The list above includes only a few of the foods and supplements that interact with various medicines. So how can you avoid food-drug interactions with your specific medicines? Here are some tips that can help:

Stay organized. Use one pharmacy for all prescriptions so that your pharmacist can keep track of your medicines and warn you of possible interactions. Store all medicines, vitamins, and supplements in their original containers for easy identification. Throw out expired medicines, and do not take old medicines that are not currently prescribed by your physician.

You can also stay organized by using a spreadsheet to keep track of your medicines, vitamins, and supplements. Include information such as the size and shape of pills and tablets, possible side effects and interactions, and the dates when you began taking the drug, vitamin, or supplement. Bring this record with you to doctor’s appointments for easy reference.

Be informed. Read the drug information sheet that accompanies your medicine to find instructions about food-drug interactions, and contact your health care professional if you have any questions. Visit the Web sites below for more information about food-drug interactions.

  • This comprehensive guide to food-drug interactions [PDF] is published by the U.S. Food and Drug Administration.
  • This medical record form [PDF] can help you keep track of your medicines.
  • Medline Plus has valuable information about specific drugs and supplements, including dosages, side effects, and precautions.
  • This privately owned Web site has a drug interaction checker: www.drugs.com.

Talk with your healthcare professional. Although the sources above may provide useful information, never stop taking your medicines or change the dose without consulting your doctor.

Notify your doctor and pharmacist of all vitamins, prescription drugs, over-the-counter drugs, and supplements that you are taking. Also tell your doctor if you are on a special diet or considering a new diet.

Be sure to ask your doctor or pharmacist about potential interactions when taking a new medicine or when instructed to change the frequency or dose of a current medicine. Ask if your medicine can interact with foods, beverages, over-the-counter drugs, or other prescribed medicines.

— M. Yeoman

For more information, talk to your physician, visit www.mdanderson.org, or call askMDAnderson at 877-632-6789.

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