Sotalol hydrochloride (MJ 1999) is an adrenergic β-antagonist that is used in the treatment of life-threatening arrhythmias. Sotalol hydrochloride is a competitive beta adrenoceptor antagonist devoid of membrane-stabilizing activity and intrinsic sympathomimetic activity that has no preferential actions on beta 1 or beta 2 responses. Sotalol hydrochloride causes concentration-dependent increases in the contractility of isolated ventricular tissue that is not blocked by previous beta or alpha blockade or catecholamine depletion. Sotalol hydrochloride consistently reduces the heart rate to a greater degree than propranolol and causes significantly less cardiac suppression than propranolol at a given heart rate.
Sotalol hydrochloride is not only a beta blocker but a class III antiarrhythmic drug. Its possible antifibrillatory activity was therefore investigated in both the ventricles and atria of dog heart in situ, since vulnerability to fibrillation is not the same in both these parts of the myocardium.