Learning Objective

Describe the pharmacology of adrenergic antagonists, including nonselective and selective α-blockers, their clinical uses, adverse effects, and important physiologic correlations involving β-blocker withdrawal and glucagon’s cardiac actions.

Nonselective α Antagonists (α₁ + α₂ blockers)

Phentolamine:

• Competitive antagonist

Phenoxybenzamine:

• Noncompetitive antagonist
• Uses: preoperative management of pheochromocytoma
• Adverse effects: hypotension, reflex tachycardia

Selective α Antagonists

α₁ blockers:

• Prazosin, Doxazosin, Terazosin
• Used in hypertension, BPH

α₁A blocker:

• Tamsulosin
• Used in BPH (prostate-selective)

α₂ blocker:

• Mirtazapine
• Used in depression

Clinical Correlates

Clinical Correlates

Activity