It is highly active at all of the muscarinic receptors, but has little effect on the nicotinic receptors.<unk>  has a charged quaternary amine structure, rendering it insoluble to lipid cell membranes. Clinically, this means that it will not cross the blood–brain barrier and has poor absorption from the gastrointestinal tract. It is broken down at a relatively slow rate within the body, due to its relative resistance to acetylcholinesterases. The chemical structure of<unk>  is identical to acetylcholine but with a methyl group on the beta carbon (hence being called acetyl-β-methylcholine), this β-methyl group provides selectivity towards muscarinic receptors as compared to nicotinic receptors. The quaternary ammonium group is essential for activity. The ester makes it susceptible to the enzyme acetylcholine esterase.
Methacholine
Bromethalin
Theobromine
Dicycloverine
Glycopyrronium bromide
Allergan
Acetyl chloride
Guaifenesin