Which antidote reactivates acetylcholinesterase after organophosphate poisoning?

• A. Atropine
• B. Activated Charcoal
• C. N-acetylcysteine
• D. Pralidoxime

Answer: (D)

Pralidoxime is the antidote that reactivates acetylcholinesterase after organophosphate exposure. Organophosphates inhibit the enzyme by phosphorylating its active site, causing excessive acetylcholine buildup. Pralidoxime binds to the phosphorylated enzyme and removes the phosphate group, restoring enzyme activity. This reactivation works best if given soon after exposure, before aging of the enzyme occurs, which would make reactivation impossible. By comparison, atropine only blocks acetylcholine receptors to reduce symptoms, activated charcoal can limit absorption but doesn’t restore enzyme function, and N‑acetylcysteine is used for a different toxicity (acetaminophen) and has no role here.