Competitive neuromuscular blockers Anticholinesterases

Anticholinesterases oppose the actions of competitive neuromuscular blockers (e.g. tubocurarine) and can therefore be used as an antidote to restore muscular activity following their use. Conversely, anticholinesterases increase and prolong the actions of the depolarising neuromuscular blockers (e.g. suxamethonium (succinylcholine)). Anticholinesterases used to treat Alzheimer s disease may also interact with neuromuscular blockers. 

The depolarising blockers (such as suxamethonium (succinylcholine)) act like acetylcholine to depolarise the motor endplate, but unlike acetylcholine, they are not immediately removed by cholinesterase. The anticholinesterase drugs increase the concentration of acetylcholine at the neuromuscular junction, which enhances and prolongs this type of blockade, and therefore anticholinesterases cannot be used as an antidote for this kind of blocker. Care should be taken if an anticholinesterase has been given to antagonise a competitive neuromuscular block prior to the use of suxamethonium, as the duration of the suxamethonium block may be prolonged. ... 

The manufacturer warns that irinotecan could possibly prolong the neuromuscular blocking effects of suxamethonium (succinylcholine) and antagonise the neuromuscular blockade of competitive (non-depolarising) drugs. This is based on the fact that irinotecan has anticholinesterase activity (see also Neuromuscular blockers + Anticholinesterases , p. 114, for an explanation of this mechanism). 

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