II. Indications

III. 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

IV. 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)

V. 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

VI. Precautions

  1. Consult toxicology (esp. if more than one dose is needed)

VII. 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

VIII. 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

IX. References

  1. (2016) CALS Manual, 14th ed, 1:133
  2. Orman and Hatten in Herbert (2016) EM:Rap 16(4): 6

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Ontology: Physostigmine (C0031849)

Definition (MSH) A cholinesterase inhibitor that is rapidly absorbed through membranes. It can be applied topically to the conjunctiva. It also can cross the blood-brain barrier and is used when central nervous system effects are desired, as in the treatment of severe anticholinergic toxicity.
Definition (CSP) cholinergic alkaloid with anticholinesterase activity used topically to produce pupillary constriction and decrease of intraocular pressure in glaucoma and parenterally to reverse the CNS effects produced by overdosage of anticholinergic drugs.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D010830
SnomedCT 373347005, 85429009
English Physostigmine, Pyrrolo(2,3-b)indol-5-ol, 1,2,3,3a,8,8a-hexahydro-1,3a,8-trimethyl-, methylcarbamate (ester), (3aS-cis)-, physostigmines, physostigmines (medication), Physostigmine [Chemical/Ingredient], physostigmine, Physostigmine (product), Physostigmine (substance), PHYSOSTIGMINE
Swedish Fysostigmin
Czech fysostigmin
Finnish Fysostigmiini
Japanese エゼリン, フィゾスチグミン, 硫酸フィゾスチグミン
Polish Fizostygmina, Ezeryna
Spanish fisostigmina (producto), fisostigmina (sustancia), fisostigmina, Fisostigmina
French Physostigmine
German Physostigmin
Italian Fisostigmina
Portuguese Fisostigmina