Inhibition of suxamethonium relaxation by tubocurarine and gallamine pretreatment during induction of anaesthesia in man.

The effect of tubocurarine and gallamine pretreatments on suxamethonium relaxation was measured in 81 patients. The blocking effect of a constant infusion of suxamethonium (0.58 mg/sec) on the recorded thumb adduction in response to supramaximal ulnar nerve stimulation was reproducible in 18 control subjects: infusion time for 50% block was 37.7 (+/- SEM 1.02) sec. Tubocurarine 3 mg and 6 mg increased the infusion time required to produce 50% block by 33.4 and 54.8% respectively. Gallamine had a similar effect. Clinical conditions for endotracheal intubation were evaluated on a blind basis. Both drugs produced impairment of clinical conditions for intubation after suxamethonium 60 mg infusion. However, when pretreatment by tubocurarine 3 mg was followed by suxamethonium infusion at 1 mg/sec the time course of neuromuscular blockade was identical to that of the controls. There were no fasciculations with this dosage and conditions for endotracheal intubation were excellent.