Class III Antiarrhythmic Drugs

Class III antiarrhythmic drugs (AADs) predominantly block outward-repolarizing potassium currents and prolong cardiac action potential duration (APD) and refractoriness at concentrations at which they do not affect the sodium channels and, therefore, intracardiac conduction velocity is not significantly affected. The prolongation of the APD and refractoriness, combined with the maintenance of normal conduction velocity, leads to an increase in the wavelength of the cardiac impulse, defined as the distance travelled by the depolarization wave during the functional refractory period, closes the excitable gap in the reentrant circuit and suppresses reentry. Class III AADs include: amiodarone, dofetilide, dronedarone, ibutilide and sotalol.