What is the action of pralidoxime in organophosphate poisoning?

• A. Reactivates acetylcholinesterase
• B. Antidote for organophosphate poisoning
• C. Absorbs toxins
• D. Blocks acetylcholine receptors

Answer: (A)

Pralidoxime reactivates acetylcholinesterase that has been inactivated by organophosphates. Organophosphates covalently modify the active-site serine of acetylcholinesterase, preventing it from hydrolyzing acetylcholine and leading to excess ACh at both muscarinic and nicotinic synapses. Pralidoxime binds to the inhibited enzyme and removes the phosphate group, restoring the enzyme’s activity and allowing acetylcholine breakdown to resume. This helps reverse the peripheral cholinergic symptoms, especially when given early, before the enzyme–organophosphate complex undergoes aging, after which reactivation becomes unlikely. While it is the specific antidote for organophosphate poisoning, it does not absorb toxins and does not block acetylcholine receptors—that latter action is what drugs like atropine do.