Ambenonium chloride tetrahydrate is a salt of ambenonium --- a quaternary ammonium compound with parasympathomimetic activity. It is a cholinesterase inhibitor used in the management of myasthenia gravis. Myasthenia gravis occurs when the body produces antibodies against acetylcholine receptors, and thus inhibits signal transmission across the myoneural junction. Ambenonium chloride is a rapid indirect-acting cholinergic agonist that reversibly blocks the activity of acetylcholinesterase, thereby prevents acetylcholine hydrolysis and prolonging its activity on nicotinic receptors at the neuromuscular junction.