NEOSTIGMINE (59-99-4)

Neostigmine is a parasympathomimetic, specifically, a reversible cholinesterase inhibitor.It is available under several trade names such as Prostigmin and Vagostigmin. By interfering with the breakdown of acetylcholine, it indirectly stimulates both nicotinic and muscarinic receptors. Unlike physostigmine, Neostigmine has a quarternary nitrogen; hence, it is more polar and does not enter the CNS. its effect on skeletal muscle is greater than that of physostigmine, and it can stimulate contractility before it paralyzes. Neostigmine has short duration of action, usually thirty minutes to two hours. Neostigmine binds to the anionic site of cholinesterase. The drug blocks the active site of acetylcholinesterase so the enzyme can no longer break down the acetylcholine molecules before they reach the postsynaptic membrane receptors. This allows for the threshold to be reached so a new impulse can be triggered in the next neuron. In myasthenia gravis there are too few acetylcholine receptors so with the acetylcholinesterase blocked, acetylcholine can bind to the few receptors and trigger a muscular contraction. It can induce generic occular side effects including: headache, brow pain, blurred vision, phacodinesis,pericorneal injection, congestive iritis, various allergic reactions, and rarely, retinal detachment and it will cause slowing of the heart rate (bradycardia), for this reason it is usually given along with a parasympatholytic drug such as atropine or glycopyrrolate.Gastrointestial symptoms occur earliest after ingestion and include anorexia, nausea and vomiting, abdominal cramps and diarrhea.