ISOBOLOGRAPHIC AND DOSE-RESPONSE ANALYSIS OF THE INTERACTION BETWEEN PIPECURONIUM AND VECURONIUM

We have studied the neuromuscular effects of pipecuronium, vecuronium and their combination in 130 ASA group I or II patients. Patients were anaesthetized with 0.8 % halothane and 60 % nitrous oxide in oxygen. Neuromuscular block was recorded as the evoked thenar mechanomyographi c response to train-of-four stimulation of the ulnar nerve (2 Hz at 10 -s intervals). The dose-response curves were determined by probit anal ysis. The calculated doses producing 50 % depression of the first twit ch height were 15.6, 16.9 and 15.0 mug kg-1 for the pipecuronium, vecu ronium and pipecuronium-vecuronium combination groups, respectively. I sobolographic and algebraic (fractional) analyses were used to assess quantitatively the combined neuromuscular effect of pipecuronium and v ecuronium and to define the type of interaction between these drugs. T he interaction between pipecuronium and vecuronium was found to be add itive.