Many people enjoy the health benefits of grapefruit or grapefruit juice as part of their daily breakfast routine. These citrus fruits provide a natural source of vitamin C and fiber. However, people who are taking prescription medications need to be aware of the possibility of an interaction between their medicine and grapefruit. This interaction was identified in the late 1980s. Some patients were initially advised just to separate the dose of medication from the grapefruit juice, but it is now known that grapefruit or grapefruit juice cannot be consumed at all while taking certain prescriptions.
How Grapefruit Juice Affects Drugs
Most medications enter the body through the mouth and are broken down by enzymes in the intestines and the liver. Natural chemicals in grapefruit block the activity of one of these enzymes, known as CYP3A4. This enzyme helps to break down several commonly used medications. When the chemicals in grapefruit juice blocks the enzyme, this can lead to changes in blood levels of the medicine. In some cases, levels of the medication will become too high and occasionally, too low.
Prescription Medications Affected by Grapefruit
Not all medications interact with grapefruit. Most prescriptions and over-the-counter medications will not be affected. Some commonly used medications that patients do need to watch with grapefruit juice include:
- amiodarone (Cordarone, Pacerone) for heart
- simvastatin (Zocor) and lovastatin (Mevacor, red yeast rice) for cholesterol
- nifedipine (Adalat, Procardia) and verapamil (Calan) for blood pressure
- tacrolimus (Prograf) for immunosuppression
- triazolam (Halcion) and midazolam (Versed) for twilight sleep before a procedure
- erythromycin for infection and gastroparesis
According to Pharmacy Times, some of these interactions can be dangerous. Nilotinib (Tasigna) is an oral medication used to treat leukemia. The prescribing information for nilotinib notes that grapefruit juice can block breakdown of this medication which could lead to a fatal heart arrhythmia known as long QT syndrome. Erythromycin is used as an antibiotic and to increase digestion of food in gastroparesis. Combining grapefruit with erythromycin can also lead to a heart arryhthmia.
Further Information on Grapefruit Juice and Medications
The Florida Department of Citrus has published a handy chart for patients to use to check their medications and the severity of the potential interaction. Anyone with questions on consuming grapefruit with their specific prescriptions should contact their pharmacist or prescriber. Alternative medications may be available to use instead.
Sources:
Shimomura, S. Drug Interactions with Grapefruit Juice: An Evidence-Based Overview. Pharmacy Times. 2006. Accessed March 30, 2010.
Grapefruit Interactions Quick Check. The Florida Department of Citrus. 2010. Accessed March 30, 2010.
Grapefruit-Drug Interaction Information for Patients. Center for Drug Interaction Research and Education. druginteractioncenter.org. Accessed March 30, 2010.
Tasigna Important Safety Information. us.tasigna.com. Accessed March 30, 2010.
Melissa Murfin - Melissa is a physician assistant in endocrinology with a further specialization in thyroid and parathyroid disorders. She is also a ...
