Disopyramide (Dicorantil) is a class IA antiarrhythmic drug with efficacy in ventricular and atrial arrhythmias. Disopyramide blocks the fast inward sodium current of cardiac muscle and prolongs the duration of cardiac action potentials. Disopyramide inhibits HERG encoded potassium channels. Disopyramide also exhibits complex protein binding, and has a potent negative inotropic action.