Which medication is used to treat urinary retention related to anticholinergic effects, especially in older men with BPH?

• A. Bethanechol
• B. Atropine
• C. Oxybutynin
• D. Diphenhydramine

Answer: (A)

Urinary retention from anticholinergic effects happens because blocking muscarinic receptors reduces detrusor muscle contraction, making it harder to push urine out. The way to counter this is to stimulate those same receptors on the bladder to boost detrusor activity. Bethanechol is a direct-acting muscarinic agonist that increases detrusor muscle tone and relaxes the bladder outlet, promoting urination. This is exactly the mechanism needed to overcome anticholinergic-induced retention, especially in older men where there may be some degree of obstruction from BPH but retention is due to underactive detrusor rather than a complete blockage. Other options either block muscarinic receptors (which would worsen retention) or have anticholinergic effects themselves (which also worsen retention). Thus bethanechol best fits the goal of relieving this type of retention.