Adrenergic alpha-1 Receptor Antagonists
Overview
Overview
Alpha-1 antagonists competitively block postsynaptic alpha-1 receptors in vessels and the lower urinary tract. Vascular selectivity and alpha-1A uroselectivity influence clinical use.
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Classification
Classification
Non-uroselective agents include prazosin, doxazosin and terazosin. Tamsulosin and silodosin are relatively alpha-1A selective; alfuzosin is functionally uroselective despite limited receptor-subtype selectivity.
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Mechanism of action
Mechanism of action
Blockade reduces Gq-mediated smooth-muscle contraction, causing vasodilation and relaxation of prostate and bladder-neck smooth muscle.
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Important members
Important members
Prazosin, doxazosin, terazosin, tamsulosin, alfuzosin and silodosin are important examples.
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Clinical uses
Clinical uses
Uses include benign prostatic hyperplasia and selected hypertension. Prazosin is also used in specialist settings for PTSD-associated nightmares and Raynaud phenomenon.
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Adverse effects
Adverse effects
Dizziness, postural hypotension, syncope, headache and nasal congestion may occur. Tamsulosin and silodosin can cause ejaculatory dysfunction, and exposure is associated with intraoperative floppy iris syndrome.
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Contraindications and precautions
Contraindications and precautions
Start cautiously in patients with hypotension or high fall risk. Patients planning cataract surgery should disclose current or previous alpha-1-blocker use.
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References
- Nachawati D, Patel JB. Alpha-Blockers. NCBI Bookshelf. Updated 2025. SOURCE:NCBI:ALPHA_BLOCKERS:2025