A 55-year-old woman with overactive bladder (OAB) is prescribed oxybutynin. The most common reason patients discontinue oxybutynin therapy is:

• A Urinary incontinence unresponsive to treatment
• B Tachyphylaxis developing within the first week
• C Intolerable dry mouth and constipation from systemic anticholinergic effects ✓
• D QT prolongation leading to cardiac arrhythmias

Explanation

Oxybutynin is a non-selective muscarinic antagonist with additional smooth muscle antispasmodic properties and local anesthetic activity on the bladder. Its poor selectivity means significant systemic M3 blockade causing prominent dry mouth, constipation, blurred vision, and urinary hesitancy — anticholinergic side effects that are the leading cause of discontinuation. Newer agents like solifenacin and mirabegron have better tolerability profiles.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.