A 70-year-old man taking multiple medications develops agitation, flushed dry skin, tachycardia and visual hallucinations suggestive of central anticholinergic syndrome. Which agent is the specific antidote and why?

• A Neostigmine, because it penetrates the blood-brain barrier readily
• B Edrophonium, because its short action limits overcorrection
• C Pralidoxime, because it regenerates central muscarinic receptors
• D Physostigmine, because it is a tertiary amine that crosses the blood-brain barrier ✓

Explanation

Physostigmine is a tertiary amine carbamate inhibitor of acetylcholinesterase and therefore enters the central nervous system, restoring central acetylcholine levels and reversing delirium from anticholinergic toxicity. Neostigmine and edrophonium are quaternary ammonium compounds confined to the periphery and cannot treat central symptoms. Pralidoxime reactivates phosphorylated enzyme in organophosphate poisoning and has no role here.

Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.