Which medication is a muscarinic cholinergic antagonist used to treat urge incontinence?

• A. Oxybutynin
• B. Bethanacol
• C. Tamsulosin
• D. Mirabegron

Answer: (A)

Urge incontinence comes from involuntary, overactive contractions of the detrusor muscle. Medicines that blunt these contractions by blocking muscarinic receptors in the bladder—the muscarinic cholinergic antagonists—reduce urgency and leakage. Oxybutynin is such an antimuscarinic; by blocking the M receptors on the detrusor, it decreases involuntary contractions and increases bladder capacity. That makes it the most appropriate choice for this condition.

Bethanechol is a muscarinic agonist, which would stimulate the detrusor and worsen symptoms. Tamsulosin is an alpha-1 blocker that helps with outlet flow, not detrusor overactivity. Mirabegron works by activating beta-3 receptors to relax the detrusor via a different pathway, not by antagonizing muscarinic receptors.