A clinical researcher tests a new drug that causes marked miosis, lacrimation, and salivation, but produces no skeletal muscle fasciculations. This pattern most likely indicates the drug is a selective:

• A Nicotinic NMJ agonist
• B Ganglionic blocker
• C Acetylcholinesterase inhibitor with high CNS selectivity
• D Selective muscarinic M3 agonist ✓

Explanation

Miosis (M3/M2 in iris sphincter), lacrimation, and salivation are muscarinic effects mediated primarily by M3 receptors on exocrine glands and smooth muscle. The absence of fasciculations confirms no significant nicotinic NMJ activation. A selective muscarinic M3 agonist like bethanechol produces glandular and smooth muscle effects without nicotinic stimulation. Ganglionic blockers would reduce, not increase, these secretory outputs.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.