Neostigmin

Neostigmine, sometimes written as neostigmin, is a reversible acetylcholinesterase inhibitor used in medicine to increase acetylcholine at cholinergic synapses. It is commonly employed to reverse nondepolarizing neuromuscular blockade after anesthesia and to treat myasthenia gravis, where it can improve muscle strength. It has also been used in the past to stimulate GI and urinary tract motility, though this is less common today.

Mechanism of action is through inhibition of acetylcholinesterase, the enzyme that degrades acetylcholine. By preventing breakdown, neostigmine raises acetylcholine levels at the neuromuscular junction, thereby enhancing transmission and counteracting blockade. The molecule is a quaternary ammonium compound, which limits its ability to cross the blood–brain barrier, resulting in predominantly peripheral effects.

Administration and duration vary by indication. For reversal of nondepolarizing neuromuscular blockers, neostigmine is given intravenously at a dose commonly around 0.04–0.08 mg/kg, usually coadministered with an antimuscarinic agent such as atropine or glycopyrrolate to reduce muscarinic side effects. For myasthenia gravis, it may be given orally or by injection, with dosing tailored to symptom response. Onset after IV administration is typically a few minutes, with peak effect within about 7–12 minutes and a duration of roughly 0.5–2 hours; CNS effects are minimal due to poor central penetration.

Adverse effects are primarily cholinergic in nature and may include bradycardia, hypotension, increased secretions, bronchospasm, abdominal cramping, diarrhea, sweating, and potential cholinergic crisis. Neostigmine is contraindicated in certain conditions such as mechanical obstruction of the gastrointestinal or urinary tract and in severe bronchial asthma or COPD. Drug interactions can enhance cholinergic effects with other agents that increase acetylcholine activity. See also pyridostigmine and physostigmine.