Alpha-1 Antagonists (Prazosin, Terazosin, Tamsulosin)

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Summary

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Key Points

  • Alpha-1 Antagonists
    • Drug Names
      • -osin (Prazosin, Terazosin, Doxazosin, Tamsulosin)
    • Mechanism
      • Alpha-1 Antagonist
        • Major effect is relaxation of smooth muscle (e.g. blood vessels, urinary tract)
    • Clinical Use
      • Benign Prostatic Hyperplasia (BPH)
        • Relaxation of smooth muscle in prostate can relieve urinary obstruction
      • Hypertension (except Tamsulosin)
        • Relaxation of smooth muscle in blood vessels causes vasodilation, reducing systemic vascular resistance and blood pressure
        • Tamsulosin is selective for alpha-1 receptors on the prostate, and spares the vascular smooth muscle
      • PTSD
        • May be used to prevent catecholamine signalling at alpha-1 receptors, reducing arousal
    • Adverse Effects
      • Orthostatic Hypotension
        • Often presents as lightheadedness or syncope, especially after first dose