Organophosphate poisoning — DTM&H MCQ

Correct answer: A — Atropine with pralidoxime and decontamination

The correct answer is A, atropine with pralidoxime and decontamination. The clinical picture (sweating, vomiting, wheeze, pinpoint pupils, bradycardia, fasciculations after pesticide exposure) is a classic cholinergic toxidrome from organophosphate acetylcholinesterase inhibition, causing excess acetylcholine at muscarinic (miosis, bradycardia, secretions, bronchospasm) and nicotinic (fasciculations) receptors. Atropine competitively blocks the muscarinic effects and is titrated against drying of secretions, heart rate and ventilation rather than a fixed dose. Pralidoxime is given alongside atropine to reactivate acetylcholinesterase and address the nicotinic (fasciculations, weakness) component, and decontamination (removing soaked clothing, washing skin) prevents ongoing absorption and protects staff, all of which are core elements of internationally accepted organophosphate poisoning management relevant to this rural Sri Lankan agricultural setting. Why the other options are wrong: C. Diazepam without antidotal therapy: benzodiazepines control seizures or agitation but do nothing for the muscarinic crisis; withholding atropine and pralidoxime would leave lethal bronchorrhoea and bradycardia untreated. D. Oral activated charcoal as sole treatment: charcoal may reduce further gut absorption after ingestion but is irrelevant here as the exposure is dermal/inhalational from spraying, and it does not reverse existing acetylcholinesterase inhibition or the acute cholinergic crisis. E. Intravenous artesunate: this is antimalarial therapy for severe falciparum malaria and has no role in a cholinergic toxidrome; nothing in the stem suggests malaria. B. Naloxone alone: naloxone reverses opioid toxicity (miosis with respiratory depression and sedation), but bradycardia, fasciculations, sweating and wheeze are not features of opioid overdose and naloxone would not correct the underlying enzyme inhibition. Key point: pinpoint pupils plus bradycardia, sweating and fasciculations after pesticide exposure signals organophosphate poisoning, treated with atropine titrated to secretions, pralidoxime, and decontamination.

Reference: Eddleston M, Buckley NA, Eyer P, Dawson AH. Management of acute organophosphorus pesticide poisoning. The Lancet, 2008. https://www.thelancet.com/journals/lancet/article/PIIS0140673607612021/fulltext