How do antimuscarinic medications help manage urge incontinence?

• A. They block muscarinic receptors in the detrusor muscle, reducing involuntary contractions and urgency
• B. They increase detrusor contractions
• C. They cause sedation
• D. They enhance bladder capacity by increasing sphincter tone

Answer: (A)

Antimuscarinic medications help manage urge incontinence by dampening the bladder’s overactivity. The detrusor muscle, when activated by acetylcholine binding to muscarinic receptors (mainly M3), contracts to empty the bladder. In urge incontinence, these contractions can occur involuntarily during filling, causing sudden urgency and leakage. By blocking these muscarinic receptors, antimuscarinics reduce involuntary detrusor contractions, allowing the bladder to store more urine and decreasing urgency, frequency, and leakage. This can also increase overall bladder capacity.

Side effects come from blocking muscarinic receptors elsewhere in the body, leading to dry mouth, constipation, and blurred vision, and sometimes cognitive effects in susceptible individuals. These medications do not work by increasing detrusor contractions, nor do they primarily sedate or raise sphincter tone.