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Physostigmine

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Physostigmine

  • See Also
  1. Anticholinergic Toxicity
  • Indications
  1. Incapacitating Agent exposure (e.g. BZ, Agent 15)
  2. Anticholinergic Overdose (e.g. Diphenhydramine, Atropine)
  • Pharmacokinetics
  1. Reversibly binds Acetylcholinesterase (short-acting Acetylcholinesterase Inhibitor)
  2. Related to Pyridostigmine
  3. Lasts only 30 to 60 minutes
  4. May require frequent redosing as below
  • Routes
  1. Intramuscular
    1. Adults: 0.05 mg/kg
    2. Child: 0.02 mg/kg
  2. Intravenous
    1. Dose: 0.02 mg/kg up to 1-2 mg
      1. Available in 2 mg/2 ml vials
      2. Dilute one 2 mg Physostigmine vial in 8 cc NS within a 10 cc syringe and infuse slowly
    2. Infuse over 2-10 minutes or slower and may repeat every 30 minutes (as often as every 10-20 min)
      1. Risk of Seizure if infused too quickly
  3. Oral: 60 mcg/kg (bitter taste, dilute in juice)
  • Protocol
  • Example in Adults
  1. Initial: 2-3 mg IM or 2 mg slow IV (see above)
  2. Repeat: every 30-60 minutes prn depressed mental status
  3. Maintenance: 2-4 mg IV slowly every 2-4 hours prn
  4. Taper: Slowly taper over hours to 4-5 days
  • Precautions
  1. Consult toxicology (esp. if more than one dose is needed)
  • Adverse Effects
  1. Bradycardia (common, related to increased vagal tone)
    1. Atropine 0.5 to 1 mg may be given to counter significant Bradycardia or bronchorrhea
  2. Bronchorrhea
  3. Vomiting
    1. Consider pretreatment with Ondansetron
  4. See Cholinergic Toxicity
  • Contraindications
  1. Cardiac conduction abnormality (Obtain EKG prior to administration)
    1. Bradycardia
    2. Intraventricular conduction delay
    3. AV Nodal block
    4. Tricyclic Overdose
      1. Physostigmine was part of coma cocktail (mix of antidotes to counter Overdose) in 1980s
      2. Physostigmine fell out of favor in general due to worse outcomes in TCA Overdose
  2. Uncontrolled Asthma or Wheezing
  3. Seizure Disorder
  • References
  1. (2016) CALS Manual, 14th ed, 1:133
  2. Orman and Hatten in Herbert (2016) EM:Rap 16(4): 6