Pharmacokinetics and Pharmacodynamics of Vecuronium and Pancuronium in Anesthetized Children

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Abstract
An intravenous bolus of vecuronium (100 μg/kg) or pancuronium (100 μg/kg) was administered. Plasma concentrations of the two muscle relaxants were determined for 6 hr after the administration by means of a fluorimetric assay followed by a thin layer chromatography. Plasma concentrations of vecuronium and pancuronium declined biexponentially in children and no metabolites could be detected in plasma. The elimination half-lives of vecuronium and pancuronium did not differ significantly. The volume of distribution at steady state (VdSS) was greater (P < 0.05) after vecuronium (320 ± 181 ml/kg; mean ± SD) than after pancuronium (203 ± 36 ml/kg). Plasma clearance of vecuronium (2.8 ± 0.9 ml·min−1 · kg−1) was greater than that of pancuronium (1.7 ± 0.2 ml · min−1 · kg−1; P < 0.05). Plasma concentrations measured at 10%, 50%, or 90% recovery of the EMG response did not differ significantly for vecuronium and pancuronium. Thus the shorter duration of action of vecuronium is probably due to its greater apparent volume of distribution, as well as to its higher plasma clearance. Thus although the elimination half-lives are comparable, the plasma disappearance of vecuronium is more rapid than that of pancuronium. Address correspondence to Dr. Meistelman, Hopital Saint Vincent de Paul, 74 avenue Denfert-Rochereau 75674 Paris Cedex 14, France. Accepted for publication July 14, 1986. © 1986 International Anesthesia Research Society...