II. Mechanism

  1. Adrenergic alpha-2 Agonist (similar to Clonidine, Dexmedetomidine) with central acting decrease in sympathetic tone
  2. Used as a Sedative, Analgesic and centrally acting Muscle relaxant in veterinary medicine
  3. Street name, "Horse Tranquilizer", added to injection Drugs of Abuse (e.g. Fentanyl, Cocaine) to enhance euphoria
  4. Associated with Opioid Overdose deaths, and unresponsive to Naloxone

III. Pharmacokinetics

  1. Typically injected, but is also well absorbed with ingested or insufflated
  2. Half-Life: 5 hours after injection
  3. Symptoms manifest with as little as 10 mg injected

IV. Findings

  1. Overdose unresponsive to Naloxone
  2. Neurologic
    1. Pupil Constriction (Miosis)
    2. Sedation
    3. Respiratory Depression
  3. Cardiovascular
    1. Bradycardia
    2. Hypotension (may follow initial Hypertension)
  4. Endocrine
    1. Hyperglycemia (mild)
  5. Skin
    1. Ulcerations at injection site

V. Labs

  1. See Unknown Ingestion
  2. Bedside Glucose
  3. No drug levels are available

VI. Diagnostics

VII. Management

  1. See Unknown Ingestion
  2. Decontamination
    1. Consider Activated Charcoal if large ingestion within prior hour and protected airway
  3. Supportive Care
    1. Naloxone for Opioid coingestion reversal
    2. Endotracheal Intubation if indicated
    3. Supplemental Oxygen
  4. Symptomatic Bradycardia
    1. Atropine
  5. Hypotension
    1. Intravenous Fluids
    2. Norepinephrine
  6. Significant Ventricular Dysrhythmia
    1. Amiodarone
    2. Lidocaine
  7. Disposition
    1. Admit all symptomatic patients (e.g. Symptomatic Bradycardia, Hypotension)
    2. May discharge if asymptomatic at 4 to 6 hours from use

VIII. References

  1. Tomaszewski (2022) Crit Dec Emerg Med 36(6): 32

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