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Mechanism Of Action

Neostigmine methylsulfate is a competitive cholinesterase inhibitor. By reducing the breakdown of acetylcholine, neostigmine methylsulfate induces an increase in acetylcholine in the synaptic cleft which competes for the same binding site as nondepolarizing neuromuscular blocking agents, and reverses the neuromuscular blockade.


Neostigmine methylsulfate-induced increases in acetylcholine levels results in the potentiation of both muscarinic and nicotinic cholinergic activity. The resulting elevation of acetylcholine competes with nondepolarizing neuromuscular blocking agents to reverse neuromuscular blockade. Neostigmine methylsulfate does not readily cross the blood-brain barrier and, therefore, does not significantly affect cholinergic function in the central nervous system.



Following intravenous injection, the observed neostigmine methylsulfate volume of distribution is reported between 0.12 and 1.4 L/kg. Protein binding of neostigmine methylsulfate to human serum albumin ranges from 15 to 25%.


Neostigmine methylsulfate is metabolized by microsomal enzymes in the liver.


Following intravenous injection, the reported elimination half-life of neostigmine methylsulfate is between 24 and 113 minutes. Total body clearance of neostigmine methylsulfate is reported between 1.14 and 16.7 mL/min/kg.

Renal impairment

Elimination half-life of neostigmine methylsulfate was prolonged in anephric patients compared to normal subjects; elimination half-life for normal, transplant and anephric patients were 79.8 ± 48.6, 104.7 ± 64 and 181 ± 54 min (mean ± SD), respectively.

Hepatic impairment

The pharmacokinetics of neostigmine methylsulfate in patients with hepatic impairment has not been studied.


Elimination half-life of neostigmine methylsulfate in infants (2-10 months), children (1-6 years) and adults (29-48 years) were 39 ± 5 min, 48 ± 16 min, and 67 ± 8 min (mean ± SD), respectively. Observed neostigmine methylsulfate clearance for infants, children and adults were 14 ± 3, 11 ± 3 and 10 ± 2 mL/min/kg (mean ± SD), respectively.

Drug Interaction Studies

The pharmacokinetic interaction between neostigmine methylsulfate and other drugs has not been studied.

Clinical Studies

The evidence for the efficacy of neostigmine methylsulfate for the reversal of the effects of nondepolarizing neuromuscular blocking agents after surgery is derived from the published literature. Randomized, spontaneous-recovery or placebo-controlled studies using similar efficacy endpoints evaluated a total of 404 adult and 80 pediatric patients undergoing various surgical procedures. Patients had reductions in their recovery time from neuromuscular blockade with neostigmine methylsulfate treatment compared to spontaneous recovery.

Last reviewed on RxList: 10/30/2015
This monograph has been modified to include the generic and brand name in many instances.

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