What happens when you take amiodarone with grapefruit?
Amiodarone is a class III antiarrhythmic used for life-threatening ventricular arrhythmias and atrial fibrillation. It has an extraordinarily long half-life (weeks to months), wide tissue distribution, and a long list of potential adverse effects involving the thyroid, lungs, liver, eyes, and skin. Its therapeutic window is narrow, and clinicians titrate carefully.
Amiodarone is extensively metabolized by CYP3A4 to N-desethylamiodarone (N-DEA), an active metabolite that contributes to both efficacy and toxicity. Grapefruit and grapefruit juice contain furanocoumarins (bergamottin, 6,7-dihydroxybergamottin) that irreversibly inactivate intestinal CYP3A4 for 24-72 hours per exposure.
A controlled study in healthy volunteers published in Clinical Pharmacology & Therapeutics found that drinking grapefruit juice three times a day with a single oral amiodarone dose raised amiodarone AUC by 50 percent and peak concentration by 84 percent. Production of the active metabolite N-DEA was essentially abolished. The FDA-approved Pacerone prescribing information cites this study directly in its drug interactions section and includes an explicit instruction that grapefruit juice should not be consumed during oral amiodarone treatment.
Why is this important?
Higher amiodarone exposure increases the risk of QT-interval prolongation, torsades de pointes, bradycardia, AV block, hypotension, and the parent drug's long list of dose-related organ toxicities (thyroid dysfunction, pulmonary toxicity, hepatotoxicity, corneal deposits, blue-grey skin discoloration). At least one published case report describes a patient who developed QT prolongation and torsades de pointes after consuming large quantities of grapefruit juice during amiodarone therapy.
The loss of N-DEA matters too. Active metabolites contribute to the antiarrhythmic effect, so although amiodarone parent drug levels rise, the antiarrhythmic profile shifts in unpredictable ways. The clinical bottom line is that grapefruit makes amiodarone exposure both higher and less predictable.
This is one of the few situations where a manufacturer's label uses explicit language about a food. The Pacerone label, the patient medication guide, and the consumer-facing label all warn against grapefruit juice. This is the strongest level of evidence we have for any drug-food interaction.
What should you do?
Do not eat grapefruit or drink grapefruit juice while taking oral amiodarone. The effect of grapefruit lasts for days, so spacing the juice and the pill apart does not prevent the interaction. Also avoid Seville oranges (often used in marmalade), pomelos, and tangelos, all of which contain the same furanocoumarins. Standard sweet oranges, mandarins, lemons, and limes do not contain meaningful furanocoumarin levels and are fine.
If you have already been consuming grapefruit during amiodarone therapy, tell your cardiologist or pharmacist. They may want to recheck an ECG (looking specifically at the QTc interval), recheck liver and thyroid function (already monitored regularly for amiodarone), and consider whether your dose needs adjustment. Stop the grapefruit immediately and allow the enzyme to regenerate over the following 3-7 days.
Which specific products are affected?
Oral amiodarone is sold under the brand name Pacerone and as generic amiodarone tablets. Intravenous amiodarone, used in hospital settings, bypasses intestinal CYP3A4 and is not subject to the grapefruit interaction; the warning applies to oral therapy.
Forms of grapefruit that contain the interacting compounds include whole grapefruit (fresh or canned), fresh-squeezed grapefruit juice, refrigerated or shelf-stable bottled grapefruit juice, frozen concentrate, and any beverage or food made with real grapefruit. Seville oranges, pomelos, and tangelos contain similar furanocoumarins. Other amiodarone food and drug interactions to consider include the inducers (rifampin, St. John's wort, phenytoin) that can lower its level, and inhibitors (other CYP3A4 inhibitors such as clarithromycin and ritonavir) that further raise its level.
The bottom line
Amiodarone and grapefruit is one of the few drug-food interactions explicitly contraindicated on an FDA-approved label. Grapefruit juice raises amiodarone exposure by approximately 50 percent and erases the active metabolite, with documented risk of QT prolongation and torsades. Do not eat grapefruit, drink grapefruit juice, or consume Seville oranges, pomelos, or tangelos while taking oral amiodarone. If you have been consuming grapefruit, stop and tell your cardiologist so they can recheck your ECG and lab work.