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Grapefruit & Antibiotics

author image Aubri John
Aubri John has been a contributing researcher and writer to online physical and mental health oriented journals since 2005. John publishes online health and fitness articles that coincide with her licensed clinical skills in addictions, psychology and medical care. She has a master's degree in clinical social work and a Ph.D. in health psychology.
Grapefruit & Antibiotics
Avoid grapefruit when taking antibiotics due to possible interactions. Photo Credit Zedcor Wholly Owned/PhotoObjects.net/Getty Images

Enjoying the occasional glass of grapefruit juice or sliced grapefruit for breakfast can be healthy and harmless. But if you take prescription medications, including antibiotics, you may need to squelch your consumption of grapefruit for the course of treatment. Grapefruit and medication interactions occur because of an enzyme in the fruit that prohibits the drug from metabolizing properly. Consult your physician regarding food-drug interactions before taking prescribed antibiotics.

Grapefruit-Medication Interaction

According to a 2004 journal publication from the University of Rochester Medical Center, the list of medications with which grapefruit interacts is more extensive than previously thought and can be fatal. The enzyme cytochrome P-450 3A4 in the liver metabolizes both grapefruit and many medications. Your liver can get overwhelmed by the additional substances in grapefruit, so the medication may not get processed effectively and become toxic to your body.


Antibiotic medications treat bacterial infections by killing microorganisms or stopping them from reproducing. Your physician prescribes a specific antibiotic based on the bacterial strain causing your diagnosed condition. Several classes of antibiotics exist and between each class are hundreds of specific drugs. The class of antibiotics known to interact with grapefruit are referred to as macrolides and include clarithromycin, erythromycin and troleandomycin. These medications are used to treat systemic or local infections including streptococcal, respiratory or syphilis infections.

Grapefruit and Antibiotic Research

A 2001 study published in the "European Journal of Clinical Pharmacology" studied the effects of grapefruit juice in six male subjects taking a full course of erythromycin at a 400 mg daily dose. The results of the study confirmed that the medication effects were amplified by the grapefruit juice. A 2007 study published in the "British Journal of Clinical Pharmacology" found that the antibiotic clarithromycin in 250 mg daily doses also interacted with grapefruit juice and had the added effect of raising blood glucose levels in study subjects.

Safe Use of Antibiotics

Not all antibiotics have been tested for interactions with grapefruit; consult your physician about possible medication interactions. Antibiotics are generally prescribed for short-term treatment. When you are taking antibiotics, avoid grapefruit products and any other foods or drugs advised by your physician. You may experience side effects of taking antibiotics including diarrhea or upset stomach. Consult your physician for recommendations if you have discomfort from side effects.

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