Medicine & USMLE

-osin Drugs

Alpha & Beta Blockers (New)
  1. Phentolamine
  2. Phenoxybenzamine
  3. -osin Drugs
  4. Beta-1 Selective Beta Blockers
  5. Dual Alpha Beta Blockers
  6. Mirtazapine


The -osin drugs include the drug names prazosin, terazosin, doxazosin, and tamsulosin. These drugs work as selective alpha-1 blockers.  Clinically, these drugs are most commonly used to treat BPH. Prazosin may be used to treat PTSD, and all -osin drugs except tamsulosin may also be used to treat hypertension. Side effects of the -osin drugs include first-dose orthostatic hypotension, dizziness and headaches.

Key Points

  • Alpha-1 Blockers (-osin Ending)
    • Drug Names
      • -osin ending
        • Prazosin
        • Terazosin
        • Doxazosin
        • Tamsulosin
    • Mechanism
      • Alpha-1 Antagonist
        • Major effect is relaxation of smooth muscle (e.g. blood vessels, urinary tract)
    • Clinical Use
      • Treats Benign Prostatic Hyperplasia (BPH)
        • Relaxation of smooth muscle in prostate can relieve urinary obstruction
      • Treats 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
      • Treats PTSD (Prazosin)
        • May be used to prevent catecholamine signaling at alpha-1 receptors, reducing arousal
    • Side Effects
      • 1st-Dose Orthostatic Hypotension
        • Often presents as lightheadedness or syncope, especially after first dose
      • Dizziness
      • Headache