Paper I
2022 July (Supplementary) (2019 Scheme) · 100 marks · 180 min

Question

Pharmacotherapy of Organophosphorous poisoning

Q124 marksShort Answers

Answer

Organophosphates irreversibly inhibit acetylcholinesterase, causing acetylcholine accumulation at muscarinic and nicotinic synapses.

  • General measures: remove from the contaminated area, decontaminate skin (soap and water), maintain airway/breathing/circulation, suction secretions, oxygen.
  • Atropine — competitively blocks muscarinic receptors, reversing bronchorrhoea, bronchospasm, bradycardia, and excessive secretions; titrated to effect (drying of secretions), often requiring large repeated doses. Does not reverse nicotinic effects (muscle weakness).
  • Pralidoxime (2-PAM) — a cholinesterase reactivator, displaces the organophosphate from acetylcholinesterase, reversing both muscarinic and nicotinic effects, but only if given before the enzyme-organophosphate complex “ages” (becomes irreversibly bound) — most effective when given early, alongside atropine.
  • Diazepam — controls seizures/agitation, shown to reduce mortality when given alongside atropine and pralidoxime.

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