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.
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:
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
All new medicines are tested for problems caused by
grapefruit juice before they are approved by the Food and Drug Administration
(FDA). 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.
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.
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.
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
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.
You can take steps to
avoid problems with grapefruit juice and your medicine.
This website 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
Abramowicz M (2004). Drug interactions with grapefruit juice. Medical Letter on Drugs and Therapeutics, 46(1173): 2–4.
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.
Pronsky ZM, Crowe JP (2012). Clinical: Food-drug interactions. In LK Mahan et al., eds., Krause's Food and the Nutrition Care Process, 13th ed., pp. 209–228. St Louis: Saunders.
Other Works Consulted
Grapefruit (2011). 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.
Whitney E, Rolfes SR (2011). Nutrient-drug interactions. Understanding Nutrition, 12th ed., pp. 599–603. Belmont, CA: Wadsworth.
March 9, 2012
E. Gregory Thompson, MD - Internal Medicine
& Theresa O'Young, PharmD - Clinical Pharmacy
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