Grapefruit Juice and Medicines

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Grapefruit Juice and Medicines

Overview

How does grapefruit juice affect medicines?

Grapefruit juice contains chemicals that can cause problems with enzymes that break down certain types of medicines in your intestines. When a medicine does not get broken down properly in the intestines, you can have too much medicine in your blood. Having too much medicine in your blood increases your chances of having side effects.

Which medicines are affected by grapefruit juice?

Most medicines are not affected by grapefruit juice. And not all medicines for the health problems listed below are affected by grapefruit juice. But more than 50 medicines are affected by grapefruit juice. These can include medicines for:

  • Abnormal heart rhythm.
  • Allergies.
  • Anxiety.
  • Asthma.
  • Blood clots.
  • Cancer.
  • Cough.
  • Depression.
  • Emphysema.
  • Epilepsy.
  • Erectile dysfunction.
  • Heart attack or heart disease.
  • High blood pressure.
  • High cholesterol.
  • HIV.
  • Infection.
  • Pain.
  • Enlarged prostate.
  • Stroke.

Ask your doctor how your medicines are affected by grapefruit juice and if you need to make any changes to avoid problems.

Is grapefruit juice safe for you?

If you regularly drink grapefruit juice, ask your doctor or pharmacist if any of your medicines are affected by grapefruit juice. If your medicine is making you feel sick or is causing unusual or uncomfortable side effects, talk to your doctor.

All new medicines are tested for problems caused by grapefruit juice before they are approved by Health Canada's Therapeutic Products Directorate (TPD). Medicines that are affected by grapefruit juice must have warnings in their patient information sheets. When you pick up a new medicine, your pharmacist will talk to you or give you written information about foods to avoid while taking your medicine. Some medicines may also have warnings on the "food-drug interactions" section of the bottle label.

In general, the more grapefruit juice you have, the greater the possible effects.1 It has been shown that even one glass of grapefruit juice—at any time of the day—is enough to cause certain medicines to work differently than they are supposed to.2 Sometimes the effects of one glass of juice can last up to 3 days.

In many cases, you may be able to have a glass of grapefruit juice without problems. Ask your doctor or pharmacist how much is safe for you.

What can happen if grapefruit juice affects your medicine?

The problems you may have from taking medicines that are affected by grapefruit juice depend on the kind of medicine you are taking and how your body reacts. Some problems are mild, while others are more serious. In general, older people are more likely than younger people to have serious problems.

For example, if you are taking a medicine for high blood pressure, you may develop dangerously low blood pressure. If you are taking a medicine for high cholesterol, you may develop increased side effects.

For more specific information on the kinds of health problems you could have if you drink grapefruit juice while taking a certain medicine, talk to your doctor or pharmacist.

How can you prevent problems?

You can take steps to avoid problems with grapefruit juice and your medicine.

  • Before you take any medicine, ask your doctor or pharmacist if you can safely drink grapefruit juice.
  • Read the labels on foods and natural health products to make sure they do not contain grapefruit, grapefruit juice, or grapefruit extract. You may also want to avoid Seville oranges (which are sometimes used in marmalade but not in orange juice), pomelos, and tangelos. Some studies have shown that they too can cause problems.3
  • Always read the warning labels for any medicine you are taking. If you have questions, ask your doctor or pharmacist.
  • Tell your doctor if you are having unusual or uncomfortable side effects from your medicine.
  • Tell your doctor and other health professionals about all the medicines you are taking. This includes herbs, vitamins, homeopathic products, supplements, and over-the-counter medicines.

Other Places To Get Help

Organizations

Consumer Health Products Canada: Golden Rules for Using Medicines Wisely
1111 Prince of Wales Drive
Suite 406
Ottawa, ON K2C 3T2
Phone: (613) 723-0777
Fax: (613) 723-0779
Email: info@chpcanada.com
Web Address: www.chpcanada.ca/index.cfm?fuseaction=main.DspSubPage&PageID=89&SubPageID=2204&fkMainPage=0
 

This webpage provides a list of rules to help patients use medicines wisely.


Food and Drug Administration (FDA): Consumer Health Information
10903 New Hampshire Avenue
Silver Spring, MD  20993
Phone: 1-888-INFO-FDA (1-888-463-6332)
Web Address: www.fda.gov/consumer/default.htm
 

This Web site has health information for people of all ages. Topics include the following: medicines, food and nutrition, medical devices, cosmetics, and animal health. Spanish materials are also available.


Health Canada: Healthy Living
Web Address: www.hc-sc.gc.ca/hl-vs/index-eng.php
 

Health Canada's webpage on sexually transmitted infections provides information to help you make informed choices about your health in areas such as healthy eating, physical activity, pregnancy, mental health, and sexual and reproductive health. You'll also find information intended for specific groups, such as children, women, and seniors, and for specific areas of interest, including travel, injury prevention, and substance use and abuse.


References

Citations

  1. Abramowicz M (2004). Drug interactions with grapefruit juice. Medical Letter on Drugs and Therapeutics, 46(1173): 2–4.
  2. Dahan A, Altman H (2004). Food-drug interaction: Grapefruit juice augments drug bioavailability—Mechanism, extent and relevance. European Journal of Clinical Nutrition, 58(1): 1–9.
  3. Pronsky ZM, et al. (2008). Drug metabolism section of Assessment: Food-drug interactions. In LK Mahan, S Escott-Stump, eds., Krause's Food and Nutrition Therapy, 12th ed., pp. 438. St. Louis, MO: Saunders Elsevier.

Other Works Consulted

  • Grapefruit (2004). In A DerMarderosian, J Beutler, eds., Review of Natural Products. St. Louis: Wolters Kluwer Health.
  • Prior R (2006). Phytochemicals. In ME Shils, M Shike, eds., Modern Nutrition in Health and Disease, 10th ed., pp. 582–594. Philadelphia: Lippincott Williams and Wilkins.
  • Health Canada (2006). It’s your health: The effects of grapefruit and its juice on certain drugs. Available online: http://www.hc-sc.gc.ca/hl-vs/iyh-vsv/food-aliment/grapefruit-pamplemousse-eng.php.
  • Whitney E, Rolfes SR (2011). Nutrient-drug interactions. Understanding Nutrition, 12th ed., pp. 599–603. Belmont, CA: Wadsworth.

Credits

By Healthwise Staff
Primary Medical Reviewer Kathleen Romito, MD - Family Medicine
Primary Medical Reviewer Anne C. Poinier, MD - Internal Medicine
Specialist Medical Reviewer Brian D. O'Brien, MD - Internal Medicine
Last Revised July 20, 2011

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.