Flecainide is a Vaughan Williams class 1c antiarrhythmic. It slows conduction of the action potential by acting as a potent sodium channel blocker (specifically the Nav1.5 sodium channels). This may be reflected by widening of the QRS complex and prolongation of the PR interval.

The Cardiac Arrhythmia Suppression Trial (CAST, 1989) investigated the use of agents to treat asymptomatic or mildly symptomatic premature ventricular complexes (PVCs) post myocardial infarction. The hypothesis was that this would reduce deaths from ventricular arrhythmias. Flecainide was actually shown to increase mortality post-myocardial infarction and is, therefore, contraindicated in this situation.


  • Atrial fibrillation
  • SVT associated with accessory pathway e.g. Wolf-Parkinson-White syndrome

Adverse effects

  • Negatively inotropic
  • Bradycardia
  • Proarrhythmic
  • Oral paraesthesia
  • Visual disturbances


  • Post myocardial infarction
  • Structural heart disease: e.g. heart failure
  • Sinus node dysfunction; second-degree or greater AV block
  • Atrial flutter