Flecainide (Dosage)

Flecainide is an antiarrhythmic drug used in the treatment and prevention of cardiac arrhythmias of various origins. Its metabolism mainly involves CYP2D6 and clinical guidelines recommend dose adjustment according to the metabolizing profile for this cytochrome.

Flecainide is a class Ic antiarrhythmic stabilizing membrane drug that interferes with the rapid influx of sodium during depolarization of the myocardial cell, without affecting the duration of the action potential.


Hypersensitivity to flecainide.

In patients with heart failure, with history of myocardial infarction with asymptomatic ventricular ectopy or asymptomatic non-sustained ventricular tachycardia.

Flecainide is contraindicated in patients who have suffered from cardiogenic shock; long-term atrial fibrillation, in patients in which no attempt has been made to convert sinus rhythm, in hemodynamically significant valve heart disease patients and in patients suffering from Brugada syndrome.

If no cardiac pacing measures are available, do not administer in sinus node dysfunction, atrio-ventricular conduction defects, grade two or higher atrio-ventricular blockade, branch blockade or distal blockade.


Cautions should be exercised when prescribing flecainide in patients with hepatic insufficiency and renal insufficiency, when prescribing in the elderly, children under 12 years of age, patients with hypo and hyperkalemia, severe bradycardia, pronounced hypotension, acute atrial fibrillation after cardiac surgery.

Flecainide increases the risk of mortality after a myocardial infarction in patients with asymptomatic ventricular arrhythmia. It can cause proarrhythmic effects, and may cause new arrhythmias or worsen existing ones.

In case of development of ECG alterations that could indicate a Brugada syndrome, suspend treatment. Flecainide decreases the stimulation sensitivity of the endocardium, therefore, should be used with caution in all patients with permanent pacemakers or temporary stimulation electrodes.


Astenia, fatigue, fever, edema, malaise, anorexia.

In addition, atrio-ventricular blockade of second and third degree, bradycardia, heart failure/congestive heart failure, chest pain, hypotension, acute myocardial infarction, palpitation, pause or sinus arrest and tachycardia may occur.

Allergic reactions of the skin, erythropenia, leucopenia and thrombocytopenia, vertigo, dizziness, headache, blurred or double vision and dyspnea.


It is not recommended to prescribe flecainide in concomitance with paroxetine or together with another drug that inhibits CYP2D6 cytochrome.

The clearance of flecainide can be diminished by concomitant treatment with quinidine.

Additive negative inotropic effects with: propranolol and sotalol.

Adverse effects increased by amiodarone.

Do not use with other blockers of the Ca channels.

The plasma concentrations of flecainide are increased by: SSRI (Selective Inhibitors of Serotonin Reuptake Antidepressants) and by quinine.

Risk of arrhythmias increased by concomitant treatment with: tricyclic antidepressants (TCAs), clozapine, and bupropion.

Risk of ventricular arrhythmias increased by concomitant treatment with: mizolastine, terfenadine, ritonavir, lopinavir and indinavir.

The plasma concentrations of flecainide are diminished by concomitant treatment with: phenytoin, phenobarbital and carbamazepine.

The cardiac toxicity of flecainide increases in concomitance with diuretics.

The metabolism of flecainide is diminished by the ingestion of cimetidine.


  • Apocard ®

Genes analyzed



Doki K, Homma M, Kuga K, et al . CYP2D6 genotype affects age-related decline in flecainide clearance: a population pharmacokinetic analysis. Pharmacogenet Genomics. 2012 Nov;22(11):777-83.

Palmen R, Sandritter T, Malloy-Walton L, et al . Case report: use of therapeutic drug monitoring and pharmacogenetic testing as opportunities to individualize care in a case of flecainide toxicity after fetal supraventricular tachycardia. Front Pediatr. 2023 Jun 28;11:1168619.

Poh BH, Lee JH, Abdul Haium AA, et al . Complete Heart Block Secondary to Flecainide Toxicity: Is It Time for CYP2D6 Genotype Testing? Pediatrics. 2020 Jul;146(1):e20192608.

Tamargo J, Le Heuzey JY, Mabo P . Narrow therapeutic index drugs: a clinical pharmacological consideration to flecainide. Eur J Clin Pharmacol. 2015 May;71(5):549-67. doi: 10.1007/s00228-015-1832-0.

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