Grapefruit and Medicines: A Possible Deadly Mix?
Love Grapefruit Juice? Drug Interactions Are Numerous.
Medications can interact with all forms of grapefruit - the fresh fruit, juice or even the frozen concentrate can result in problems. Interactions may occur with commonly used drugs - such as those that lower cholesterol, treat high blood pressure, or fight cancer.
What Causes These Dangerous Drug Interactions with Grapefruit?
Drug levels rise because grapefruit compounds known as furanocoumarins can block cytochrome P450 3A4 (CYP3A4) enzymes.
These enzymes, involved in the metabolism of over 50 percent of all drugs, are needed to break down drugs for elimination from the body. Some interactions are theoretical, based on their mechanism of action, but a warning is still important.
What If I Just Take My Drug At A Different Time From Grapefruit?
Even drugs that are only given once a day cannot be separated from the grapefruit effect. If you need to avoid grapefruit while you are taking a certain drug, it is best not to consume grapefruit at all.
Can I Eat Other Kinds of Citrus Fruits?
These fruits also contain furanocoumarins that may cause the same interactions as grapefruit.
Drinking grapefruit, apple and orange juice with an antihistamine called fexofenadine (Allegra) may lead to decreased levels of fexofenadine, meaning your antihistamine may not work as well. Take fexofenadine with water and avoid drinking large amounts of grapefruit, orange, or apple juice.
How Much Grapefruit or Juice Does it Take to Cause the Interaction?
One whole fruit or 200 milliliters of juice (less than one cup) can block the CYP3A4 enzymes and lead to toxic blood levels of the drug. For example, when a common blood pressure medicine by the name of felodipine (Plendil) is taken with grapefruit juice instead of water blood levels of the drug can triple.
There are many possible interactions, so be sure to tell your healthcare provider if you drink grapefruit juice and about all of your medicines, including over-the-counter (OTC) and herbal products.
What are the Most Common Drugs that Cause a Grapefruit Interaction?
- statin cholesterol medications (atorvastatin, lovastatin, simvastatin)
- drugs that are used to stabilize heart rhythms (amiodarone, dronedarone)
- and certain high blood pressure medications called calcium channel blockers (nifedipine, verapamil, felodipine)
Not all drugs in a certain class of medications have these interactions, so usually your healthcare provider can select an alternative medication.
What Kind of Effects Can Occur with Grapefruit-Drug Interactions?
Other reactions may occur - it depends on the drug and the levels of the drug in the blood.
If you have been warned about a possible drug interaction with grapefruit, ask your healthcare provider to describe the possible side effect and learn how to recognize it.
Who is Most at Risk for Grapefruit Interactions?
Discuss all of your prescription, over-the-counter (OTC), and herbal medications with your healthcare provider every time a new drug is prescribed, and tell them if you eat grapefruit or drink grapefruit juice.
Which Drugs are Most Dangerous to Take with Grapefruit Juice?
How to Best Avoid Dangerous Grapefruit Interactions?
If you discover that you are at risk for an interaction with a drug you currently take, call your healthcare provider to determine the best course of action.
It may be that the interaction is minor and no course of action is needed.
Alternatively, you may need to avoid grapefruit or your healthcare provider may need to prescribe an alternate drug.
Finished: Grapefruit and Medicines: A Possible Deadly Mix?
- Bailey DG, Dresser G, Arnold M, et al. Grapefruit-medication interactions: Forbidden fruit or avoidable consequences? CMAJ. 2012; DOI:10:1503/cmaj.120951
- Hansten PD, Horn JR. The Top 100 Drug Interactions. A Guide to Patient Management. 2013 Edition. H&H Publications. Freeland, WA.
- Shimomura S, Wanwimolruk S, Chen J. Drug Interactions with Grapefruit Juice: An Evidenced-Based Overview. Pharmacy Times. 2/1/2003. - https://secure.pharmacytimes.com/lessons/200303-02.asp