6.14 : Adrenergic Antagonists: Pharmacological Actions of β-Receptor Blockers

β-receptor blockers significantly impact the cardiovascular system by counteracting catecholamine-induced sympathetic responses. These medications decrease heart rate, contractility, and cardiac output, potentially leading to cardiac depression, life-threatening bradycardia, and death. Therapeutically, β-blockers function as mild antihypertensives and are utilized in treating angina pectoris and cardiac arrhythmias. However, nonselective β-blockers inhibit β₂-receptors in bronchial smooth muscle, resulting in bronchoconstriction, which can be detrimental to patients with asthma or obstructive lung diseases.

In addition to cardiovascular benefits, β-blockers manage exaggerated sympathetic responses in conditions such as pheochromocytoma and thyrotoxicosis. They also play a role in chronic migraine prevention, exhibit anti-anxiety properties, and hinder sympathetically induced lipolysis and insulin release, as demonstrated by propranolol. Propranolol, in particular, is highly effective in treating severe infantile hemangioma. Furthermore, these drugs treat chronic open-angle glaucoma by decreasing aqueous humor production, ultimately reducing intraocular pressure. However, it is essential to note that β-blocker treatment can cause CNS-related side effects, including fatigue, forgetfulness, sleep disturbances, and depression. Overall, β-blockers offer a wide range of therapeutic applications, but it is crucial to consider their potential side effects and contraindications when determining the most suitable treatment option.