A 62-year-old man with benign prostatic hyperplasia and overactive bladder is started on a muscarinic antagonist. The drug chosen has the highest selectivity for the M3 receptor in the bladder with minimal M2-mediated cardiac effects. Which drug best fits this description?

• A Oxybutynin
• B Tolterodine
• C Trospium
• D Darifenacin ✓

Explanation

Darifenacin is a selective M3 muscarinic antagonist, making it preferred when minimizing cardiac (M2) side effects such as tachycardia is important. Oxybutynin is non-selective and crosses the blood-brain barrier causing CNS effects. Tolterodine is a non-selective muscarinic antagonist with some tissue selectivity for the bladder. Trospium is a non-selective quaternary ammonium compound that does not cross the BBB but lacks M3 selectivity.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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