Neuromuscular block: atracurium and vecuronium compared and combined

The neuromuscular blocking action of atracurium and vecuronium acting separately and in combination have been compared using the evoked EMG of the adductor pollicis muscle. Dose response curves have been drawn for the drugs given separately and found to be nonparallel (P less than 0.05). Atracurium was calculated to be 5.25 and 4.1 times less potent than vecuronium, ED50 and ED95 respectively. The effect on neuromuscular transmission of a combined medication using equipotent doses of atracurium and vecuronium, determined from the dose response plots, was found to be greater than would be expected by addition of their separate actions. The combination of small doses resulted in significant neuromuscular blockade.