Adrenergic Antagonists

Abstract

While the sympathetic nervous system is essential for vital physiological functions, overactivity in certain pathological states causes significant morbidity and mortality. Adrenergic antagonists block the action of catecholamines on the adrenergic receptors. Phenoxybenzamine and phentolamine are non-specific alpha blockers while prazosin and its derivatives block the alpha 1 receptors with some specificity. Alpha receptor blockade is particularly helpful in patients with pheochromocytoma and other conditions where the blood pressure is dangerously high. Localization of subtypes of alpha receptors on the bladder outlet makes it possible to relieve urinary retention of benign prostatic hyperplasia while more specific treatments can work. Beta blockers have become extremely useful drugs especially because of the favorable actions in patients with certain cardiovascular diseases. Nonselective beta blockers have been rapidly replaced by more specific and useful beta 1 receptor blockers. Propranolol is the prototypical nonselective beta blocker. Due to its adverse action on the lipid profile and the bronchi, it has been replaced by generations of beta 1 specific receptor blockers some of which are still in active development. Proper understanding of the physiological alterations caused by adrenergic blockers is essential for the effective clinical management while minimizing adverse drug reactions.