USMLE

Midodrine

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Sympathomimetics and Sympatholytics
  1. Dopamine
  2. Fenoldopam
  3. Dobutamine
  4. Epinephrine
  5. Norepinephrine
  6. Isoproterenol
  7. Midodrine
  8. Phenylephrine and Pseudoephedrine
  9. (Alpha) Methyldopa
  10. Clonidine (and Guanfacine)
  11. Tizanidine

Summary

Midodrine is a selective activator or agonist of alpha-1 adrenergic receptors. Alpha-1 activity then induces systemic vasoconstriction, which is useful in the treatment of orthostatic hypotension.

Key Points

  • Midodrine
    • Mechanism of Action
      • Alpha-1 Agonist
        • Arterial Vasoconstriction → Increased TPR
        • Venous Vasoconstriction → Increased Venous Return → Increased Cardiac Output
    • Clinical Use
      • Autonomic Insufficiency
      • Orthostatic Hypotension
        • Alpha 1-mediated venous vasoconstriction helps maintain venous return despite the effects of gravity from standing up
    • Adverse Effects
      • May exacerbate supine hypertension (can be extrapolated from its clinical use)