USMLE

Clonidine (and Guanfacine)

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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

Clonidine is an alpha 2 activating drug used to treat hypertensive urgency and ADHD. Stopping clonidine quickly may cause rebound hypertension.

Key Points

  • Clonidine, Guanfacine
    • Mechanism
      • Centrally-acting alpha-2 receptor agonists
        • Sympatholytic (inhibits fight-or-flight response)
        • ↓ central adrenergic outflow lowering neuronal norepinephrine release to the heart and systemic circulation
    • Indication
      • Hypertension
        • Including hypertensive urgency
      • ADHD
        • Second-line after stimulants (e.g. methylphenidate)
      • Tourette Syndrome
        • Specifically for intractable tics associated with TS
      • Symptom control in opioid withdrawal
    • Side Effects
      • Rebound hypertension with abrupt cessation
      • CNS depression
        • Bradycardia, hypotension, respiratory depression, miosis
      • Impotence
      • Does not decrease renal blood flow (MB)