Comparison of the effects of neostigmine and edrophonium on the duration of action of suxamethonium.

Rapid sequence induction of anaesthesia necessitating the use of suxamethonium may occasionally be needed soon after antagonism of neuromuscular block with anticholinesterase agents. The onset and duration of action of 1 mg kg-1 of suxamethonium was recorded in groups of 10 patients each, 5 or 10 min after the administration of edrophonium 1 mg kg-1 or neostigmine 40 micrograms kg-1 given for the antagonism of atracurium-induced neuromuscular block. Plasma cholinesterase activity was measured before, and 5 and 10 min after the administration of the anticholinesterases. A further 10 patients received suxamethonium 1 mg kg-1 without prior atracurium or anticholinesterase administration to serve as controls. The onset of action of suxamethonium was significantly prolonged when administered 5 min after both anticholinesterases, compared to the control group (P < 0.01). Recovery of suxamethonium block was delayed significantly after neostigmine, compared to both the edrophonium and the control groups (P < 0.05-0.001). Plasma cholinesterase activity was significantly reduced with the use of neostigmine but not with edrophonium (P < 0.001).