Neuromuscular blocking effects of atracurium, vecuronium and pancuronium during bolus and infusion administration.

The potencies of atracurium, vecuronium and pancuronium were compared using bolus injections and continuous infusions. The sizes of the bolus injections were based on previously determined cumulative dose-response relationships. Dose requirements for 90% and 50% sustained blockade were estimated by use of continuous infusion, and the corresponding plasma concentrations were measured for vecuronium and pancuronium. The effect of single bolus injections correlated well with the cumulative dose-responses, confirming relative potencies for atracurium, vecuronium and pancuronium of approximately 1:5:4. The maintenance doses (microgram kg-1 h-1) for 90% blockade were: atracurium 382.8, vecuronium 101.9, and pancuronium 36.9, making the relative dose requirements 10.4:2.8:1. The same dose ratio was found for atracurium and vecuronium at 50% blockade. This required about 60% of the doses needed for maintenance of 90% response. The relative potency of vecuronium and pancuronium in plasma was 1.1:1. The 25-75% recovery index was significantly shorter for vecuronium than for atracurium.