Acetylcholinesterase Inhibitors

Background

Acetylcholinesterase inhibitors include organophosphates (can be in insecticides), carbamates, physostigmine, rivastigmine, and donezepil.  These result in increased acetylcholine which stimulate muscarinic and nicotinic receptors giving the characteristic muscarinic toxidrome described below. Nicotinic stimulation can result in tachycardia as well as muscle paralysis.

 

Evaluation

  • Physical Exam: Diarrhea/Diaphoresis, Urination, Miosis, Bronchorrhea/Bronchospasm, Bradycardia, Miosis, Emesis, Lacrimation, Salivation. (DUMBBELS mnemonic)
  • Laboratory abnormalities:  Standard lab tests are not helpful.
  • ECG:  Sinus bradycardia

 

Management

  • Atropine, Pralidoxime, Benzodiazepines 

 

  • Titrate atropine to drying secretions (can require large amounts i.e. 50 mg).
  • Bronchorrhea is excessive watery mucous from the lungs and is not the same as excess saliva from drooling. Bronchorrhea is life-threatening as patients essentially drown in their own secretions. Atropine dries secretions and is used to treat bronchorrhea.
  • Pralidoxime should be used for organophosphate poisoning to reactivate the acetylcholinesterase enzyme and is also effective against the nicotinic effects of anticholinesterase inhibition. The nicotinic effects of acetylcholinesterase inhibitors can result in muscle weakness. Pralidoxime use for other acetylcholinesterase inhibitors should be used only with Poison Control/Medical Toxicology guidance.
  • Benzodiazepines are recommended for treatment of seizures

 

Quick dosing reference: if patient has bronchorrhea:

  • Atropine: 1-3 mg IVP repeated every 2-20 minutes or 1mg followed by doubling doses every 5 minutes until bronchorrhea is no longer present followed by an infusion 10-20% of the loading dose per hour (max 2 mg/hour)
  • Pralidoxime: 2g loading dose followed by 1 g/hr infusion 

Diazepam: 5-10 mg IV every 10-15 minutes to max dose of 30 mg, can be repeated in 2-4 hours if needed