Learning Objective
By the end of this section, medical students preparing for USMLE Step 1 should be able to classify α-blockers by receptor selectivity, identify their key clinical applications, and recognize characteristic adverse effects commonly tested in exam scenarios.
Nonselective α-Blockers (α₁ + α₂)
Phenoxybenzamine
- Action: Irreversible α-blocker
- Clinical use:
- Preoperative management of pheochromocytoma to prevent catecholamine-induced hypertensive crisis
- Adverse effects:
- Orthostatic hypotension
- Reflex tachycardia
Phentolamine
- Action: Reversible α-blocker
- Clinical uses:
- Hypertensive crisis due to tyramine ingestion in patients on MAO inhibitors
- Severe cocaine-induced hypertension (second-line)
- Treatment of norepinephrine extravasation
- Adverse effects:
- Orthostatic hypotension
- Reflex tachycardia
α₁-Selective Blockers (–osin drugs)
Prazosin, Terazosin, Doxazosin, Tamsulosin
- Clinical uses:
- Benign prostatic hyperplasia (BPH) – improves urinary flow
- Hypertension (all except tamsulosin)
- Post-traumatic stress disorder (PTSD) – prazosin reduces nightmares
- Adverse effects:
- First-dose orthostatic hypotension
- Dizziness, headache
α₂-Selective Blocker
Mirtazapine
- Clinical use:
- Major depressive disorder
- Adverse effects:
- Sedation
- Increased appetite and weight gain
- Increased serum cholesterol
Activity
USMLE Step 1 Pearls
- Phenoxybenzamine is the classic pre-op drug for pheochromocytoma
- α₁-blockers end in “-osin” and cause first-dose hypotension
- Mirtazapine = sedation + weight gain (often used when insomnia is present)
