Grapefruit Juice May Interact with Many Medications, Public Citizen Warns

Drinking grapefruit juice while taking certain medications may be a bad mix, according to a report by the prominent consumer group Public Citizen. 

In the July 2012 issue of Public Citizen’s Worst Pills, Best Pills Newsletter, the group updated warnings about the risk of drug interactions with grapefruit juice, providing a list of 82 medications that may be impacted by the grapefruit juice, resulting in either too much or too little of the drug entering the blood stream.

The report was issued after information was released by the FDA in February 2012, noting new research that found grapefruit juice may decrease the effectiveness of some drugs. Public Citizen had initially warned about the risk of dangerous interactions with grapefruit juice in their Worst Pills, Best Pills Newsletter in February 2004.

Grapefruit juice can interact with many drugs that are broken down (metabolized) with the help of a vital enzyme called CYP3A4 in the small intestine.

Certain substances in grapefruit juice block the action of CYP3A4. Instead of being metabolized, more of the drug enters the bloodstream and stays in the body longer. As a result, users may experience potentially dangerous levels of the drug in your body. Because the CYP3A4 enzyme varies in amounts from one person to another, these problems could affect people differently.

Public Citizen has provided a list of drugs that may interact with, including many widely used medications, such as Lipitor, Tegretol, Propulsid, Celexa, Valium, Benadryl, Multaq, Prozac, Haldol, Serzone, Viracept, Prilosec, Paxil, Seroquel, Zoloft, Viagra, Zocor, Coumadin and others.

The consumer watchdog group has recommended that readers of their newsletter use the U.S. National Library of Medicine’s DailyMed website as a guide for drug interactions and information. DailyMed currently lists product labels for almost 40,000 drugs. The website features the most recent product labels in use and that have been submitted to the FDA for approval.

The group also recommends the following steps to find information concerning grapefruit juice and medications: After accessing the DailyMed website, enter the brand or generic name of the drug you are taking. A list of product labels will appear. Click on the drug you are taking to open the label. Once the label appears on the screen, type in “Ctrl + F” on your key board. Enter “grapefruit juice” into the find function of your Web browser. The term “grapefruit juice” will be highlighted in the document if it is discussed.