[Combination anti-arrhythmic drug therapy]

Antiarrhythmic treatment with single agents is often ineffective and can be limited by dose-dependent side-effects. Therefore, combinations of antiarrhythmic drugs in smaller and well-tolerated doses are advocated in cases refractory to single antiarrhythmic drugs. Basically, substances belonging to the same electrophysiologic class should not be combined. A combination of beta-adrenoreceptor blockers with class I antiarrhythmic drugs may be effective, mainly in cases in which the arrhythmia is dependent on adrenergic stimulation. As shown in our study, the combination of class III and I B-substances can be useful in some cases, from the electrophysiological and clinical points of view. Among the successful combinations of this type are amiodarone and mexiletine, sotalol and mexiletine, and sotalol and tocainide. In patients refractory to amiodarone alone or to a combination with mexiletine, the combined treatment with amiodarone and class-I-C drugs such as flecainide and encainide prolongs the cycle length of ventricular tachycardia, but does not suppress induction of ventricular tachycardia during programmed stimulation. Combination therapy with amiodarone and encainide is associated with a remarkable incidence of proarrhythmic effects. Nevertheless, a combination of antiarrhythmic drugs improves efficacy of therapy in selected patients. However, a close monitoring is mandatory because of the risk of proarrhythmia.