Neostigmine is a quaternary ammonium compound that does not penetrate the blood-brain barrier.

It is used to accelerate the reversal of nondepolarizing neuromuscular blockade of nicotinic receptors in the neuromuscular junction at the end of surgery. This allows acetylcholine to build up at the neuromuscular junction and overcome the competitive inhibition of nondepolarizing blocking drugs. Neostigmine inhibits acetylcholinesterase, which is the enzyme that metabolizes acetylcholine into choline and acetic acid. Neostigmine is an oxy-diaphoretic inhibitor of the acetylcholinesterase enzyme, which means that it binds and inhibits via acid-transferring (or binding to the anionic site of the enzyme creating a covalent bond). Acetylcholine is metabolized by an enzyme called acetylcholinesterase that hydrolyzes acetylcholine in the neuromuscular junction-neostigmine is one of the drugs in the class of acetylcholinesterase inhibitors. Acetylcholine is the neurotransmitter in the body that is made, stored, and released by the end of motor nerve terminals.

Antidote midazolam