By: Gilbert A. Leidig Jr., MD, F.A.C.C.

Many of us enjoy starting our day with a glass of orange or grapefruit juice and often take medications with the juice. Several commonly used medications may rise to dangerously high levels in the blood stream when taken with grapefruit juice or with tangelos (a hybrid grapefruit) or with Seville oranges. These medications are listed below and include some high blood pressure medications, cholesterol lowering medications and amiodarone, which is used to treat atrial fibrillation and other arrhythmias.

Grapefruit juice and fresh grapefruits, as well as the oranges listed, contain a compound called furanocoumarins that decrease the amount of cytochrome P450 3A4 in the intestine. This enzymes break down and inactivates the listed drugs, but has little effect on other medications. The susceptible drugs may accumulate to high levels in the bloodstream increasing their effectiveness and in some patients who are particularly sensitive, causing toxic effects such as muscle damage from high levels of statin drugs. It is important to note that most prescription drugs are not affected by grapefruit juice and no interactions have been observed with nonprescription medications.(1)

Below are some commonly asked questions and answers regarding grapefruit juice and medication usage.(2)
*Does fresh grapefruit also interact with certain medications?
The components in grapefruit juice responsible for suppressing the CYP3A enzyme are also found in fresh grapefruit, and may cause interactions with the same medications affected by grapefruit juice.

*How much grapefruit juice would a person have to drink to cause a problem?
The amount of grapefruit juice necessary to cause an interaction can vary by individual and affected medication – from ordinary servings to very large quantities, such as a quart a day.

*Will an interaction only occur if I swallow an affected medication along with grapefruit juice?
Current scientific research to date indicates that an interaction may occur for up to 72 hours after consuming grapefruit juice, although the degree of the interaction may diminish over this time period. Many factors, such as individual health and prescription type, can influence the potency of the medication and potential effects of an interaction

*Is it safe to drink grapefruit juice if a certain amount of time elapses between medication doses?
Current scientific research indicates that grapefruit juice can inhibit the CYP3A enzyme in the body for up to 72 hours after consumption. We do know that once a person is no longer taking an affected drug, they can resume drinking grapefruit juice.

*If I’ve been drinking grapefruit juice with affected medications for some time with no ill effects, should I heed the warnings and stop drinking grapefruit juice now?
No, continue drinking grapefruit juice. Your medication may be stabilized, in which case the sudden elimination of grapefruit juice may create an imbalance. We can assess the potential for an interaction, which may vary, and determine whether discontinuing grapefruit consumption or switching to an alternative, non-interacting medication that offers appropriate, safe treatment is necessary.

1. Mary F. Paine et al A furanocoumarin-free grapefruit juice establishes furanocoumarins as the mediators of the grapefruit juice-felodipine interaction.” Am J Clin Nutr 2006; 83.
2. Facts about potential drug interaction with grapefruit juice. www.medicalnewstoday.com/articles/31888

Cardiology Physicians, P.A.

www.cardiocppa.com

Abby Medical Center
One Centurian Drive, Suite 200
Newark, DE 19713
302.366.8600

Foulkstone Plaza
1401 Foulk Road, Suite 201
Wilmington, DE
302.478.5055

GILBERT A. LEIDIG JR., M.D., F.A.C.C.
Dr. Leidig joined Cardiology Physicians in June of 1996. Dr. Leidig obtained a Bachelor of Science degree, Summa Cum Laude, from Loyola College in Baltimore, Maryland. He then attended the University of Pennsylvania School of Medicine. His post-graduate training in Internal Medicine came during a residency at the Walter Reed Army Medical Center in Washington, D.C. Dr. Leidig was an attending physician at Keller Army Hospital at the United States Military Academy in West Point, New York. He then did a cardiovascular fellowship at Beth Israel Hospital, Harvard Medical School, in Boston, Massachusetts. Dr. Leidig served as Chief of Cardiology at Womack Army Medical Center in Fort Bragg, North Carolina. He was a consulting associate and interventional attending at the catheterization laboratories at the Duke University Medical Center. His recognitions include membership in A.O.A., and the Best Doctors in Delaware. He is board certified in Internal Medicine, Cardiovascular Disease and Interventional Cardiology.

Dr. Leidig has a strong commitment to consultative and clinical cardiology. He has areas of interest including echocardiography, transesophageal echocardiography, and stress echocardiography. Dr. Leidig has expertise in diagnostic catheterization as well as coronary stent placement and angioplasty. He also has expertise in peripheral vascular disease and stent placement and angioplasty for the treatment of peripheral vascular disease.

Dr. Leidig and his wife Meaghen were married in 1985 and are the proud parents of Andrew, Patrick, Farrell and Molly. Our family enjoys gardening, running, swimming, birding and hiking as well as reading, trivia, stamp collecting and current events. Dr. Leidig is on the Pastoral Council at St. Mary of the Assumption Church in Hockessin and on the Salesianum School Board of Trustees.