The clinical use of class IC antiarrhythmic drugs.

Flecainide, encainide, and propafenone belong to class IC antiarrhythmic drugs. They are new and potent drugs which markedly depress Phase 0 of the action potential without affecting repolarization. Class IC drugs are very potent suppressors of premature ventricular complexes but their efficacy in the treatment of ventricular tachycardia is only comparable to that of class IA agents. Although noncardiac side effects are minimal, myocardial depression and serious proarrhythmic effects are not infrequently noted. A thorough understanding of the pharmacodynamics and toxicity potential of these drugs is therefore essential for their safe usage.