NCIt definition : The hydrochloride salt form of esmolol, a short and rapid-acting beta adrenergic antagonist
belonging to the class II anti-arrhythmic drugs and devoid of intrinsic sympathomimetic
activity. Esmolol hydrochloride competitively blocks beta-1 adrenergic receptors in
cardiac muscle and reduces the contractility and cardiac rate of heart muscle, thereby
decreasing cardiac output and myocardial oxygen demands. This agent also decreases
sympathetic output centrally and blocks renin secretion. At higher doses, esmolol
hydrochloride also blocks beta-2 receptors located in bronchial and vascular smooth
muscle, thereby leading to smooth muscle relaxation.;