Adrenergic alpha-Antagonists
Overview
Overview
Alpha antagonists block alpha-mediated smooth-muscle contraction or presynaptic feedback. Their effects depend strongly on alpha-1 versus alpha-2 selectivity.
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Classification
Classification
Major groups are irreversible and reversible nonselective alpha blockers, selective alpha-1 blockers, uroselective alpha-1A blockers and uncommon alpha-2 antagonists.
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Mechanism of action
Mechanism of action
Alpha-1 blockade lowers vascular and lower-urinary-tract smooth-muscle tone. Alpha-2 blockade increases norepinephrine release, which can produce greater tachycardia and sympathetic activation.
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Important members
Important members
Phenoxybenzamine, phentolamine, prazosin, doxazosin, terazosin, tamsulosin, silodosin and yohimbine illustrate the major subgroups.
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Clinical uses
Clinical uses
Uses include pheochromocytoma preparation or crisis management, benign prostatic hyperplasia, selected hypertension and a limited number of specialist indications.
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Adverse effects
Adverse effects
Orthostatic hypotension, dizziness, syncope, nasal congestion and sexual adverse effects are common themes. Nonselective blockade can cause pronounced tachycardia.
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Contraindications and precautions
Contraindications and precautions
Assess fall risk, volume status and concomitant vasodilators. Catecholamine-secreting tumours require specialist management and alpha blockade before beta blockade.
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References
- Nachawati D, Patel JB. Alpha-Blockers. NCBI Bookshelf. Updated 2025. SOURCE:NCBI:ALPHA_BLOCKERS:2025