Among the medications this patient takes, which is an antimuscarinic that could cause dry mouth and constipation?

Among the medications this patient takes, which is an antimuscarinic that could cause dry mouth and constipation?

• A. Oxybutynin
• B. Donepezil
• C. Amlodipine
• D. Cetirizine

Answer: (A)

Antimuscarinic drugs block muscarinic receptors, which reduces salivary secretions and slows gut motility. That combination commonly produces dry mouth and constipation. Oxybutynin is a muscarinic antagonist used to treat overactive bladder by decreasing bladder contractions. Because it blocks muscarinic receptors, dry mouth and constipation are common anticholinergic side effects, making it the best fit for this question. Donepezil increases acetylcholine levels by inhibiting its breakdown, promoting parasympathetic activity rather than blocking it, so dry mouth or constipation aren’t driven by antimuscarinic blockade in the same way. Amlodipine is a calcium channel blocker with no muscarinic receptor blockade and doesn’t typically cause dry mouth or constipation as primary anticholinergic effects. Cetirizine has antihistamine action with only modest incidental anticholinergic effects, not a primary antimuscarinic profile.

Antimuscarinic drugs block muscarinic receptors, which reduces salivary secretions and slows gut motility. That combination commonly produces dry mouth and constipation.

Oxybutynin is a muscarinic antagonist used to treat overactive bladder by decreasing bladder contractions. Because it blocks muscarinic receptors, dry mouth and constipation are common anticholinergic side effects, making it the best fit for this question.

Donepezil increases acetylcholine levels by inhibiting its breakdown, promoting parasympathetic activity rather than blocking it, so dry mouth or constipation aren’t driven by antimuscarinic blockade in the same way. Amlodipine is a calcium channel blocker with no muscarinic receptor blockade and doesn’t typically cause dry mouth or constipation as primary anticholinergic effects. Cetirizine has antihistamine action with only modest incidental anticholinergic effects, not a primary antimuscarinic profile.