DOSE-RESPONSE CURVES FOR FOUR NEUROMUSCULAR BLOCKERS USING CONTINUOUS I.V. INFUSION

Cumulative dose-response curves were constructed in man for rubocurarine, pancuronium, gallamine and alcuronium from data obtained during barbiturate-narcotic-nitrous oxide anaesthesia. Fifty-six adult patients received one of these drugs, administered by constant-rate infusion, a technique enabling full characterization of the sigmoid curve for each patient. The individual curves were solved for several response levels and the results pooled to derive a composite dose-response curve for each drug. Using the mechanical twitch response, the ED50 for each neuromuscular blocking drug was: tubocurarine 0.236 mg kg−1, pancuronium 0.048 mg kg−1, gallamine 1.3 mg kg−1 and alcuronium 0.161 mg kg−1. The slopes of the composite curves for pancuronium and alcuronium were significantly steeper than those for tubocurarine and gallamine. In the alcuronium studies the simultaneous compound electromyogram was recorded, and usually this was more depressed than the mechanical twitch response, giving an ED50 of 0.135 mg kg−1.