Methacholine chloride is a quaternary ammonium parasympathomimetic agent with the muscarinic actions of acetylcholine.

(?)-Nicotine is the dominant form of the natural alkaloid nicotine. It acts as an agonist of neuronal nicotinic acetylcholine receptors (nAChRs) and possesses addictive and teratogenic properties. (?)-(S)-Nicotine is significantly more active at binding nAChRs compared to the (+)-(R) antipode thus nicotine is typically synthesized as (?)-(S)-nicotine with only 0.2-1% of the (+)-(R) isomer present.

A class I anti-arrhythmic agent (one that interferes directly with the depolarization of the cardiac membrane and thus serves as a membrane-stabilizing agent) with a depressant action on the heart similar to that of guanidine.