A 45-year-old patient exposed to organophosphate insecticide is brought to casualty with pinpoint pupils, excessive secretions, bradycardia, muscle fasciculations, and seizures. The correct sequence of antidote administration is:

• A Pralidoxime first to regenerate AChE, then atropine for muscarinic symptoms
• B Atropine (large doses until secretions dry) THEN pralidoxime (within 24–48 hours before ageing) THEN diazepam for seizures ✓
• C Diazepam first to terminate seizures, then atropine, then pralidoxime
• D Atropine alone is sufficient; pralidoxime is only for carbamate poisoning

Explanation

In organophosphate poisoning, atropine should be given first in large titrated doses (until secretions dry — the 'atropinisation' end point) because hypoxia from bronchospasm and bronchorrhoea is the immediate life threat. Pralidoxime (2-PAM) regenerates AChE by cleaving the phosphoryl-AChE bond before 'ageing' (irreversible phosphorylation) occurs, typically within 24–48 hours. Benzodiazepines are given for seizures. Pralidoxime does NOT work for carbamate poisoning (carbamylation reverses spontaneously).

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.