USMLE

(Alpha) Methyldopa

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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

Alpha-methyldopa is an anti-hypertensive drug that works by activating the alpha-2 receptors of the central nervous system. This leads to a decrease in sympathetic output that helps to lower blood pressure. Clinically, alpha-methyldopa is used to treat hypertension in pregnant patients. However, use of alpha-methyldopa can lead to the creation of auto-antibodies that cause autoimmune hemolysis and drug-induced lupus as side effects.

Key Points

  • Alpha-Methyldopa
    • Mechanism
      • Alpha-2 Agonist
        • In brainstem: leads to reduced sympathetic outflow from spinal cord
        • On presynaptic neurons: leads to negative feedback and decreased release of catecholamines on target sites (heart, smooth muscle)
    • Clinical Use
      • Hypertension in Pregnancy
        • Decreased sympathetic outflow from spinal cord, in addition to decreased effect of catecholamines on target sites
    • Adverse Effects
      • Direct Coombs-positive Hemolysis (Warm Autoimmune Hemolytic Anemia)
      • Drug-Induced Lupus
      • Sexual Impotence