Carbachol is a structural analog of acetylcholine and has agonist activity at muscarinic and nicotinic cholinergic receptors. It is like acetylcholine in being a quaternary amine and having a positive charge at all pH values. A major difference from acetylcholine is that carbachol is not hydrolyzed by cholinesterases. Carbachol can also modulate cholinergic neurotransmission by stimulating prejunctional cholinergic receptors, which augment (nicotinic) or attenuate (muscarinic) the release of acetylcholine.
Hoover, Donald. 2007. Carbachol. xPharm: The Comprehensive Pharmacology Reference. 1-5. https://doi.org/10.1016/B978-008055232-3.61379-0 ISBN: 9780080552323