A 60-year-old man being treated with bethanechol for post-operative urinary retention suddenly develops severe abdominal cramping, sweating, and bradycardia. The best immediate treatment is:

• A Neostigmine 0.5 mg subcutaneously
• B Pralidoxime 1 g intravenously
• C Atropine 0.6 mg intravenously ✓
• D Physostigmine 1 mg intravenously

Explanation

Bethanechol is a muscarinic agonist; overdose produces exaggerated muscarinic effects (cramping, sweating, bradycardia, salivation). Atropine, a muscarinic antagonist, reverses these effects immediately and is the antidote. Neostigmine and physostigmine would worsen toxicity by further increasing acetylcholine levels, and pralidoxime is used only for organophosphate poisoning.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.