The interaction of tubocurarine and suxamethonium at different stages of recovery from tubocurarine-induced neuromuscular blockade in anaesthetized man.

The interaction of tubocurarine and suxamethonium in man was studied by the use of tetanic and single twitch contractions of the adductor pollicis muscles. Suxamethonium 0.2 mg/kg was administered at the times when the recovery of the tetanic contraction from neuromuscular blockade produced by tubocurarine 0.2 mg/kg had reached 20% and 50% of the control. At the 20% recovery point, suxamethonium improved both the tetanic and single twitch contractions; at the 50% recovery point, the single twitch response was markedly enhanced but the tetanic contraction was depressed. The findings suggest that the interaction of tubocurarine and suxamethonium is both antagonistic and synergistic. The tetanic contraction is more sensitive to the synergistic action compared with the single twitch contraction. When the interaction of these two agents is being evaluated it is important to consider the doses of the agents, the stage of curarization where the interaction took place and the method of assessing the neuromuscular blockade.