Are there any contraindications between Flecainide (anti-arrhythmic medication) and grapefruit consumption?

From the Guidelines

There is no significant contraindication between flecainide and grapefruit or grapefruit juice, as flecainide is not metabolized by the CYP3A4 enzyme system that grapefruit inhibits. Flecainide is primarily metabolized by CYP2D6, which is not affected by grapefruit compounds, as indicated in the 2015 ACC/AHA/HRS guideline for the management of adult patients with supraventricular tachycardia 1. This guideline provides crucial information on the management of supraventricular tachycardia, including the use of flecainide and its potential interactions. Some key points to consider when prescribing flecainide include:

• Monitoring PR and QRS intervals
• Considering monitoring flecainide plasma levels to keep trough plasma levels below 0.7–1.0 mcg/mL
• Avoiding use in patients with sinus or AV conduction disease (in absence of pacemaker), cardiogenic shock, structural heart disease, atrial flutter (unless concomitant AV nodal therapy to avoid 1:1 conduction), Brugada syndrome, renal dysfunction, hepatic dysfunction, or QT-prolonging drugs
• Being cautious with concomitant use of amiodarone, digoxin, ritonavir, saquinavir, tipranavir, and other medications that may interact with flecainide, as listed in the guideline 1. However, grapefruit juice is listed as a precaution for propafenone, another Class Ic antiarrhythmic agent, but not specifically for flecainide, suggesting that the interaction between grapefruit and flecainide is not a significant concern 1. Therefore, patients taking flecainide can generally consume grapefruit without concern for increased drug levels or toxicity, but should still inform their healthcare provider about all foods, supplements, and other medications they consume regularly.

From the Research

Flecainide and Grapefruit Contraindications

• There are no direct research papers to assist in answering this question regarding the interaction between flecainide and grapefruit.
• However, it is known that grapefruit can interact with certain medications, including some antiarrhythmic drugs, by inhibiting the enzyme CYP3A4, which can lead to increased levels of the medication in the blood 2, 3, 4, 5, 6.
• Flecainide is a class Ic antiarrhythmic agent, and its pharmacokinetics and pharmacodynamics can be affected by various factors, including drug interactions and patient characteristics 3, 4, 5, 6.
• The studies provided focus on the efficacy and safety of flecainide in various patient populations, including those with atrial fibrillation, supraventricular tachycardias, and catecholaminergic polymorphic ventricular tachycardia 2, 3, 4, 5, 6.
• To determine potential contraindications between flecainide and grapefruit, further research is needed to investigate the specific interaction between these two substances.

Potential Risks and Interactions

• Patients taking flecainide should be aware of potential drug interactions and inform their healthcare provider about any medications, supplements, or foods they are consuming, including grapefruit 2, 3, 4, 5, 6.
• Healthcare providers should monitor patients taking flecainide for potential side effects and adjust the dosage or discontinue treatment if necessary 2, 3, 4, 5, 6.