Acecainide (N-acetylprocainamide), the N-acetylated metabolite of procainamide, is a Class III antiarrhythmic agent. Acecainide exerts cardiac anticholinergic effect. It elicits smooth muscle relaxation mainly through the activation of plasma membrane K+ channels. Acecainide markedly reduced premature ventricular beats and prevented induction of ventricular tachycardia. Acecainide appears to offer advantages over procainamide, particularly with respect to the reduced formation of antinuclear antibodies. Acecainide development has been discontinued.