Chapter 20: Adrenergic-Blocking Drugs – Beta & Alpha Blockers

Adrenergic-Blocking Drugs – Beta & Alpha Blockers agents are classified based on the specific receptors they block: alpha blockers, beta blockers, or combined alpha-beta blockers. Alpha-adrenergic blockers primarily interrupt stimulation at alpha-1 receptors, leading to therapeutic effects such as systemic vasodilation, decreased total systemic vascular resistance, and reduced blood pressure, making them essential for treating hypertension. Furthermore, by relaxing smooth muscle in the bladder and prostate, alpha blockers like tamsulosin are effective in managing benign prostatic hyperplasia (BPH). Specific uses also include the treatment of pheochromocytoma and the reversal of local vasoconstriction caused by vasopressor extravasation, such as with phentolamine. A significant risk with alpha blockers is the first-dose phenomenon and orthostatic hypotension. Beta blockers prevent endogenous catecholamines from binding to beta receptors; cardioselective drugs target beta-1 receptors (found mainly in the heart), decreasing heart rate, myocardial contractility, and conduction, which provides crucial cardioprotection following a myocardial infarction and helps treat angina, dysrhythmias, and heart failure (e.g., metoprolol, carvedilol). Nonselective beta blockers, such as propranolol, also block beta-2 receptors (primarily in the lungs), risking adverse effects like bronchoconstriction in patients with pulmonary disease and impairing the body’s normal response to hypoglycemia. Comprehensive nursing care involves diligent cardiovascular and respiratory assessment, emphasizing slow position changes to minimize dizziness, strict adherence to prescribed doses, and the critical instruction that abrupt cessation must be avoided to prevent dangerous rebound hypertension.