Adrenergic Antagonists

Adrenergic Antagonists:

Directly block adrenergic receptors
Have high degree of receptor specificity (unlike adrenergic agonists)  two types – alpha-adrenergic blocking agents and beta-adrenergic blocking agents

Effects of alpha-adrenergic blocking agents:
• lower blood pressure by blocking alpha1 receptors on arterioles and veins  vasodilation  reduction in blood pressure
• reduced contraction of smooth muscle in bladder  used for symptomatic relief in benign prostatic hyperplasia
• pheochromocytoma  increased secretion of catecholamines  hypertension from activation of alpha1 receptors  use alpha-adrenergic blocking agents
• suppression of symptoms in Raynaud’s disease – works by preventing the alpha mediated vasoconstriction

Adverse effects of alpha-adrenergic blocking agents:
• hypotension (common side effect that limits therapeutic use)
• tachycardia

Effects of beta-adrenergic blocking agents:
• blockage of beta1 receptors in heart  decreased heart rate, decreased force of contraction, reduced velocity of impulse conduction through AV node.
• used for angina pectoris (decrease cardiac work  balance between oxygen demand and supply); hypertension; cardiac dysrhythmias (decrease rate of sinus node discharge and rate of conduction through AV node); heart failure.

Adverse effects of beta-adrenergic blocking agents:
• bradycardia
• reduction in cardiac output
• AV heart block
• 4-40% develop Raynaud’s Phenomenon