A 70-year-old woman with urinary retention after hip replacement surgery has an indwelling catheter. Ultrasound shows no mechanical obstruction and cystoscopy is normal. Which drug is most appropriate to stimulate bladder emptying?
- A Methacholine
- B Carbachol
- C Bethanechol ✓
- D Acetylcholine
Correct answer: C. Bethanechol
Explanation
Bethanechol is a muscarinic agonist with negligible nicotinic action and resistance to acetylcholinesterase, giving it a useful oral duration. Its contraction of detrusor muscle suits postoperative and postpartum non-obstructive urinary retention and neurogenic ileus. Acetylcholine is destroyed within seconds and never used systemically. Carbachol has significant nicotinic activity and is now mainly ophthalmic, while methacholine is used only as a bronchial provocation agent in asthma testing, making bethanechol the standard choice.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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