Organophosphate Poisoning

Organophosphates are substances bind irreversibly to acetylcholinesterase, causing cholinergic excess. Examples include fertilisers and sarin gas.


Effects (as expected) are signs of muscarinic and nicotinic over-activation. This can be remembered by 'BLUDGES' for the muscarinic effects:

  • Bradycardia (and subsequent hypotension)
  • Lacrimation
  • Urination
  • Defecation
  • GIT upset
  • Emesis
  • Sweating and Salivation

and 'M' for the nicotinic effects:

  • Muscular spasm


Management is aimed at reducing ACh burden:

  • Atropine
    Competitive antagonises ACh at the muscarinic receptor.
    • Atropine is preferred over glycopyrrolate as it will cross the blood brain barrier and treat central ACh toxicity
  • Pralidoxime
    Reactivates acetylcholinesterase by luring the organophosphate away from the enzyme with a tantalising oxime group.
    • Pralidoxime must be used within the first few hours of poisoning
      After which the organophosphate-enzyme group 'ages' and is no longer susceptible.
    • Does not cross the blood-brain barrier and so cannot treat central effects


  1. CICM March/May 2009
  2. Rang HP, Dale MM, Ritter JM, Flower RJ. Rang and Dale's Pharmacology. 6th Ed. Churchill Livingstone.
Last updated 2019-07-18

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