Which agent is specifically used as a reactivator of acetylcholinesterase in organophosphorus pesticide poisoning?

• A. Pralidoxime
• B. Diazepam
• C. Atropine
• D. Hydroxocobalamin

Answer: (A)

When organophosphate pesticides block acetylcholinesterase, the enzyme becomes phosphorylated and can no longer hydrolyze acetylcholine, leading to excessive cholinergic signaling. Pralidoxime reactivates the enzyme by cleaving that phosphate from the active site serine, effectively restoring acetylcholinesterase activity. This reactivation works best if given before the bond ages, a process that makes reactivation unlikely once aging has occurred. Because pralidoxime directly addresses the underlying enzyme inhibition, it is the specific antidote for this poisoning. The other agents have important roles in management—diazepam can help with seizures, atropine reduces muscarinic symptoms but doesn’t restore enzyme function, and hydroxocobalamin treats cyanide poisoning—not organophosphate cholinesterase inhibition.