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Clonidine Overdose

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Clonidine Overdose, Clonidine Toxicity, Clonidine Poisoning, Imidazoline Poisoning, Oxymetazoline Overdose, Naphazoline Overdose, Tetrahydrozoline Overdose

  • See Also
  1. Clonidine
  2. Drug Overdose
  3. Alpha Adrenergic Central Agonist
  4. Clonidine Withdrawal
  • Pathophysiology
  1. See Clonidine
  2. Clonidine acts at 2 sites
    1. Central Acting Adrenergic Agonists (alpha-2 receptors)
      1. Inhibits CNS preganglionic sympathetic signals, lowering Blood Pressure
      2. Results in increased parasympathetic effects and side effects (e.g. sedation)
    2. Imidazoline receptors
      1. Imidazoline-1 has hypotensive effects
      2. Imidazoline-2 may have Antidepressant effects (acting at MAO-A and MAO-B receptors)
      3. Imidazoline-3 appears to affect Glucose homeostasis
  3. Imidazoline Poisonings result in Clonidine-Like Toxicity (especially in children, and may be managed in similar ways)
    1. Clonidine Overdose (including Clonidine patch)
    2. Dexmedotomidine (e.g. veterinary Anxiolytic medications)
    3. Child ingestion of topicals
      1. General
        1. Very large ingestions may result when bottles are inverted
        2. Rapid absorption from Gastrointestinal Tract with effect onset in first 20-30 minutes
        3. Gastric Decontamination is typically ineffective (rapid onset) and unsafe (altered LOC)
    4. Rapid absorption
      1. Oxymetazoline (Afrin)
      2. Naphazoline (Clear Eyes)
      3. Tetrahydrozoline (Visine)
      4. Xylometazoline (Oltrivin)
  • Findings
  • Signs and Symptoms
  1. Alpha-2 Agonism
    1. Bradycardia
    2. Hypotension
      1. Brief Hypertension may result from peripheral alpha effect, but this typically resolves by presentation
    3. Hypothermia
  2. Opioid-Mimic Effects
    1. Apnea
    2. Mental status change (to Coma)
    3. Pinpoint Pupils (Miosis)
    4. Respiratory Depression
  • Differential Diagnosis
  1. See Unknown Ingestion
  2. See Miosis
  3. See Bradycardia
  4. Opioid Overdose
  • Management
  • Adults
  1. ABC Management
  2. Naloxone
    1. Indicated in respiratory depression and apnea or significant CNS depression
    2. Initial
      1. No respiratory depression: 0.1 to 0.4 mg IV or IM
      2. Respiratory depression: 1 to 2 mg IV or IM
    3. Next, if no response or incomplete response
      1. Give 2 mg IV or IM every 3-5 minutes to a total of 10 mg total maximum
      2. Redosing may be needed due to short naloxone Half-Life
  3. Atropine
    1. Indicated in severe Sinus Bradycardia
    2. Atropine 0.5 to 1 mg IV (may repeat after 3 to 5 min, up to a maximum total dose of 3 mg)
  4. Vasopressors
    1. Indicated for Hypotension refractory to Intravenous Fluids
    2. Norepinephrine or Epinephrine IV
  • Management
  • Children
  1. ABC Management
  2. Naloxone
    1. Initial
      1. No respiratory depression: 0.1 mg/kg to 0.4 mg IV or IM
      2. Respiratory depression: 1 to 2 mg IV or IM
    2. Next, if no response or incomplete response
      1. Give 2 mg IV or IM every 3-5 minutes to a total of 10-20 mg
  3. Atropine
    1. Indicated in Severe Bradycardia
    2. Start: Atropine 0.02 mg/kg up to 0.16 mg IV
    3. Maximum: Atropine 0.5 mg/kg IV
  4. Vasopressors
    1. Indicated for Hypotension refractory to Intravenous Fluids
    2. Norepinephrine or Epinephrine IV
  • Management
  • Disposition
  1. Admit all symptomatic patients
  2. May discharge if asymptomatic at 6 hours after ingestion
  • References
  1. Nordt (2025) Mailbag: Imidazoline Poisoning, EM:Rap, 1/27/2025
  2. Seger (2002) J Toxicol Clin Toxicol 40(2): 145-55 [PubMed]
  3. Lowry (2014) Clin Toxicol 52(5):454-69 +PMID: 24666288 [PubMed]