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

We have studied the neuromuscular effects of pipecuronium, vecuroniumand their combination in 130 ASA group I or II patients. Patientswere anaesthetized with 0.8% halothane and 60% nitrous oxidein oxygen. Neuromuscular block was recorded as the evoked thenarmechanomyographic response to train-of-four stimulation of theulnar nerve (2Hz at 10-s intervals). The dose-response curveswere determined by probit analysis. The calculated doses producing50% depression of the first twitch height were 15.6, 16.9 and15.0 µg kg^–1 for the pipecuronium, vecuronium andpipecuronium-vecuronium combination groups, respectively. Isobolographic and algebraic (fractional) analyses were used to assessquantitatively the combined neuromuscular effect of pipecuroniumand vecuronium and to define the type of interaction betweenthese drugs. The interaction between pipecuronium and vecuroniumwas found to be additive. (Br. J. Anaesth. 1993; 71: 556–560)