Dofetilide: a new class III antiarrhythmic agent.

Dofetilide is a new, pure class III antiarrhythmic agent that prolongs the refractory period and action potential duration without having beta-blocking or calcium channel-blocking properties, making it unique among established class III agents. Dofetilide is effective in converting atrial and ventricular arrhythmias, and in maintaining sinus rhythm after cardioversion. Interestingly, it is more effective in converting atrial flutter than atrial fibrillation. It appears to be safe in patients with left ventricular dysfunction and postmyocardial infarction. In small studies, intravenous dofetilide was superior to flecainide, procainamide and amiodarone in converting atrial fibrillation and flutter. Dofetilide can be administered orally or intravenously with no significant effect on heart rate or blood pressure, but it can prolong QT interval and cause torsade de pointes in 3% to 4% of patients receiving it intravenously and in 0.8% to 1.5% of patients receiving it orally. So far, it is recommended that therapy be initiated in hospital under electrocardiogram monitoring for at least two days, with particular care to avoid torsade de pointes in high risk patients such as women, and those with bradycardia, hypokalemia, hypomagnesia and renal dysfunction. Studies have failed to show any extracardiac side effects.