4-(M-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium (McN-A-343) is a selective muscarinic M1 receptors agonist, which leads to its widespread use as an aid to distinguish responses mediated through M₁ receptors from those utilizing M₂ or M₃ muscarinic receptor subtypes, especially in the CNS. McN-A-343 has a number of non-muscarinic actions. These include activation of some types of nicotinic acetylcholine receptors, antagonism of serotonin 5-HT₃ and 5-HT₄ receptor subtypes, inhibition of the uptake mechanism and a local anesthetic action.

Subitramine is a potent inhibitor of monoamines (serotonin, dopamine, noradrenaline) reuptake that was approved by FDA for the treatmen of obesity. Sibutramine is metabolized to metabolites M1 and M2 which are more active toward the monoamine transporters.The drug was withdrawn from the market because of clinical trial data indicating an increased risk of heart attack and stroke. It was sold under a variety of brand names including Reductil, Meridia and Sibutrex.