Grapefruit is one of nature’s many delicious treats. But could this vitamin C-rich fruit be putting you in harm’s way by dangerously interacting with your medicines?
Grapefruits are low in calories and packed with benefits. One cup of fresh grapefruit gives you a huge serving of vitamin C (79 mg), not too mention other important nutrients like vitamin A, folate, beta carotene, and lycopene.
With all of these excellent qualities in one fruit, it is hard to imagine that it can cause harm. But having a diet that includes grapefruit and taking certain medicines can negatively impact your health.
Cytochrome P-450 is a group of enzymes located throughout the body, with the largest amount found in the liver and the intestinal walls. This family of enzymes is responsible for making chemical reactions needed to breakdown many different compounds, from food to drugs. CYP3A4 is the most abundant member of the enzyme family. It is responsible for breaking down approximately 60% of the drugs we take.
When grapefruit or grapefruit juice is consumed, a compound within the grapefruit disrupts the CYP3A4 enzyme’s ability to metabolize a drug. If a drug is not adequately metabolized, higher levels of the drug may enter the bloodstream, which can lead to a potentially dangerous situation. These interactions have been observed within a few hours after consuming grapefruit and may last for up to three days. As little as eight ounces (237 milliliters) can have an effect on the metabolism of some drugs. Some other citrus fruits, such as pomelos and Seville oranges (a bitter orange used in marmalades and compotes) can have similar effects.
In light of this interaction information, would it be safer to avoid grapefruit? Although a possible drug interaction is a serious matter, giving up grapefruit may not be necessary. If you are taking any medicines and you enjoy eating grapefruit or drinking grapefruit juice, it is important that you talk with your doctor. Ask
about the possibility of interactions with any prescription or over-the-counter drug that you are taking. Your doctor may be able to prescribe a medicine that won't interact with grapefruit juice.
Below are examples of medicines that can be affected by grapefruit. Even if you do not see a medicine that you are taking on this list, ask your doctor about the possibility of an interaction with grapefruit or grapefruit juice.
|Type||Examples of Medicines|
|Calcium channel blockers||Amlodipine (eg, Norvasc)|
|Felodipine (eg, Plendil)|
|Nicardipine (eg, Cardene)|
|Nimodipine (eg, Nimotop)|
|Nisoldipine (eg, Sular)|
|Verapamil (eg, Calan, Covera-HS, Isoptin)|
|Antiarrhythmics||Amiodarone (eg, Cordarone, Pacerone)|
|Quinidine (eg, Apo-Quinidine, BioQuin, Novo-Quinidin)|
|Immunosuppressants||Cyclosporine (eg, Neoral, Sandimmune)|
|Sirolimus (eg, Rapamune)|
|Tacrolimus (eg, Prograf)|
|HMG-CoA reductase inhibitors||Atorvastatin (eg, Lipitor)|
|Lovastatin (eg, Mevacor)|
|Simvastatin (eg, Zocor)|
|HIV protease inhibitors||Saquinavir|
|Psychiatric medicines||Alprazolam (eg, Xanax)|
|Buspirone (eg, BuSpar)|
|Carbamazepine (eg, Carbatrol, Epitol, Tegretol)|
|Clomipramine (eg, Anafranil)|
|Diazepam (eg, Valium)|
|Midazolam (eg, Midazolam Syrup)|
|Sertraline (eg, Zoloft)|
|Triazolam (eg, Halcion)|
|Other medicines||Cilostazol (eg, Pletal)|
|Methadone (eg, Dolophine, Methadose)|
|Mifepristone (eg, Mifeprex)|
|Sildenafil (eg, Viagra)|
If you love grapefruit and are worried that their may be an interaction with your medicine, talk to your doctor or pharmacist.
Grapefruit/grapefruit juce drug interaction information for health professionals. University of Florida College of Pharmacy Center for Drug Interaction Research and Education website. Available at: . Accessed June 11, 2012.
Grapefruit, raw, pink and red and white, all areas. USDA National Nutrient Database for Standard Reference website. Available at: . Published 2010. Accessed June 12, 2012.
Medicine interactions with grapefruit: what you should know. Am Fam Physician. 2006;74(4):611. American Family Physician website. Available at: . Published August 2006. Accessed June 12, 2012.
Stump AL, Mayo T, Blum A. Management of grapefruit-drug interactions.
Am Fam Physician. 2006;74(4):605-608.
Verapamil. EBSCO Health Library website. Available at: . Updated August 27, 2009. Accessed December 28, 2009.
Zeratsky K. Grapefruit juice: beware of dangerous medication interactions. Mayo Clinic website. Available at: . Updated November 3, 2011. Accessed June 11, 2012.
Last reviewed June 2012 by Brian Randall, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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