flecaïnide

Flecainide, also written flecaïnide, is a class Ic antiarrhythmic agent used to treat certain supraventricular arrhythmias and some ventricular arrhythmias. It is a potent sodium channel blocker that slows conduction in atrial, ventricular, and Purkinje tissue, and is active in both sinus rhythm and reentrant circuits. It is available in oral and intravenous forms.

Mechanism of action and pharmacology: Flecainide binds to fast sodium channels in their open or inactivated states, reducing the slope of phase 0 of the cardiac action potential. This slows conduction velocity, particularly in depolarized tissue, and can widen the QRS complex on the ECG. It has relatively little effect on repolarization at therapeutic doses, but excessive levels can prolong QT and increase proarrhythmic risk. The drug is mainly metabolized by CYP2D6 and excreted renally, with a half-life typically on the order of about 20 hours in adults.

Indications and cautions: Flecainide is used to convert recent-onset atrial fibrillation or flutter to sinus rhythm in patients without significant structural heart disease, and for maintenance of sinus rhythm in selected cases of paroxysmal AF. It is contraindicated in patients with structural heart disease, ischemic heart disease, cardiomyopathy with reduced ejection fraction, or suspected conduction system disease without a pacemaker. It should not be used in second- or third-degree AV block or in shock, and it requires careful ECG monitoring.

Adverse effects and interactions: Common adverse effects include dizziness, headache, nausea, and visual disturbances. Proarrhythmia is a major concern, especially in patients with heart disease; QRS widening and initiation of new tachyarrhythmias can occur. Interactions with CYP2D6 inhibitors (eg, certain antidepressants and antiarrhythmics) can increase flecainide levels and toxicity. Care is required when used with other QT- or conduction-impairing drugs.