Bethanechol belongs to which pharmacologic class?

• A. Muscarinic agonist
• B. Beta blocker
• C. Alpha antagonist
• D. Muscarinic antagonist

Answer: (A)

Bethanechol directly stimulates muscarinic receptors, mimicking acetylcholine in the parasympathetic system. This makes it a muscarinic agonist. Its actions promote bladder contraction and increased GI motility, which is why it’s used for urinary retention and postoperative ileus. It does not block adrenergic receptors, so it’s not a beta blocker or an alpha antagonist, and it isn’t a muscarinic antagonist (which would block signaling). Bethanechol is a direct-acting cholinergic agent with minimal nicotinic activity, and as a quaternary ammonium compound it has limited CNS penetration and a longer duration than acetylcholine because it’s relatively resistant to acetylcholinesterase.