Long-term safety and efficacy of flecainide in the treatment of supraventricular tachyarrhythmias: the United States experience. The Flecainide Supraventricular Tachyarrhythmia Investigators.

Information about long-term safety and effectiveness is important for appropriate use of antiarrhythmic drug therapy. We report the results of an open-label, long-term (mean, 15 months) therapy extension for 66 patients with paroxysmal supraventricular tachycardia (PSVT) or atrial fibrillation (PAF) in whom short-term therapy in 2 controlled studies was deemed beneficial by both patient and investigator. Follow-up was accomplished by clinic visits and telephone calls. Results indicated excellent ongoing tolerance and safety. Only 3 (5%) of 66 patients discontinued therapy due to possible noncardiac adverse effects. Only 5 (7.6%) discontinued therapy due to inadequate clinical response. Only 1 discontinuation was ascribed to a worsening arrhythmia (increased frequency of sustained PAF). In PSVT patients, 75% of months were arrhythmia free; in PAF patients, 64% of months were attack free. No clinically significant laboratory, electrocardiographic, or physical abnormalities were ascribed to flecainide. Thus, the long-term safety and efficacy profile of the drug for treatment of PSVT and PAF is encouraging. This promising clinical experience is relatively small and so should be reinforced by larger patient trials in the future.