Neostigmine

Neostigmine is a parasympathomimetic, specifically, a reversible cholinesterase inhibitor. By interfering with the breakdown of acetylcholine, neostigmine indirectly stimulates both nicotinic and muscarinic receptors. It does cross the blood-brain barrier albeit poorly. 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.

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Clinical Uses

It is used to improve muscle tone in people with myasthenia gravis and routinely, in anesthesia at the end of an operation, to reverse the effects of non-depolarizing muscle relaxants such as vecuronium.

It can also be used for urinary retention resulting from general anaesthetia and to treat curariform drug toxicity.

Another indication for use is the Ogilvie syndrome which is a pseudoobstruction of the colon in critically ill patients.

Neostigmine 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.

Neostigmine is available under several trade names such as Prostigmin®.

Neostigmine was first synthesized by Aeschlimann and Reinert in 1931.

Sources

• Brenner, G. M. (2000). Pharmacology. Philadelphia, PA: W.B. Saunders Company. ISBN 0-7216-7757-6
• Canadian Pharmacists Association (2000). Compendium of Pharmaceuticals and Specialties (25th ed.). Toronto, ON: Webcom. ISBN 0-919115-76-4