Flecainide

Flecainide is a class IC antiarrhythmic medication used to prevent and treat certain tachyarrhythmias. It acts mainly by blocking fast sodium channels in cardiac tissue, reducing conduction velocity in atrial and ventricular myocardium and decreasing excitability. On the electrocardiogram, this often manifests as widening of the QRS complex. The drug has little effect to shorten the action potential and can be proarrhythmic, particularly in susceptible hearts.

Indications for flecainide include maintenance of sinus rhythm in patients with paroxysmal atrial fibrillation or flutter after successful cardioversion and suppression of certain ventricular arrhythmias in selected individuals. It is generally reserved for patients without significant structural heart disease and should be used with caution in those with ischemic heart disease or prior heart failure.

Contraindications and cautions include structural heart disease (such as reduced ejection fraction or prior myocardial infarction), significant conduction system disease without a pacemaker, and a history of Brugada syndrome or pre-excitation (WPW) with atrial fibrillation, where flecainide can promote dangerous arrhythmias. It is also avoided in acute coronary syndromes and in patients with severe renal or hepatic impairment without dose adjustment. Pregnancy safety is not established; use in pregnancy is discretionary based on risk-benefit assessment.

Pharmacokinetics and dosing: flecainide is administered orally with high bioavailability and a typical half-life of about 20 hours, metabolized mainly by hepatic CYP2D6 and excreted renally. Usual dosing ranges from 50 mg twice daily to about 100 mg twice daily, with a maximum around 300 mg per day; dose and frequency are adjusted for age and renal function. Monitoring includes ECG for QRS widening and rhythm assessment, with attention to proarrhythmic symptoms and interactions. Notable drug interactions include CYP2D6 inhibitors, which can raise flecainide levels and increase toxicity.