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Beta-adrenergic blocking agents prevent stimulation of the beta-1 adrenergic receptors at the nerve endings of the sympathetic nervous system and therefore decrease the activity of the heart. They block sympathetic stimulation of the heart and reduce systolic pressure, heart rate, cardiac contractility and output, which in turn decreases the demand by the heart for oxygen and increases exercise tolerance. Beta-adrenergic blocking agents may also affect beta-2 adrenergic receptors located in the bronchial smooth muscle of the airways, which has the potential to cause bronchoconstriction (a narrowing of the breathing passages).

Cardioselective beta blockers have a clinical advantage in that they are 20 times more potent at blocking beta-1 receptors than beta-2 receptors. They are therefore less likely to cause bronchoconstriction compared with non-selective beta-blockers; however, the danger of bronchoconstriction cannot be totally ignored, as they are not totally selective.

Beta-adrenergic blocking agents are used to treat angina, control abnormal heart rhythms and to reduce high blood pressure.