Pipecuronium and pancuronium: comparison of pharmacokinetics and duration of action

The pharmacokinetics of pipecuronium 0.07 mg kg-1 and pancuronium 0.1 mg kg-1 were compared in 39 ASA class I or II patients. Plasma concentrations of these agents were measured for 6 h following administration, using a sensitive and specific capillary gas chromatographic assay. Concentration v. time data were analysed by non-linear regression and fitted to a two- or three-compartment model as appropriate. Neuromuscular blockade was assessed by measuring the mechanical evoked response of the adductor pollicis muscle to train-of-four stimulation of the ulnar nerve. Pipecuronium had a larger steady-state volume of distribution (Vss) (309 (SD 103) ml kg-1) and greater plasma clearance (Cl) (2.4 (0.6) ml kg-1 min-1) than pancuronium (199 (54) ml kg-1 and 1.5 (0.4) ml kg-1 min-1, respectively). The volumes of the central compartment, distribution and elimination half-lives and mean residence times were similar for both agents and within the range expected for drugs of this type. The durations of action (injection to 25% recovery of twitch tension) of pipecuronium and pancuronium were similar: 98.0 (36.1) min and 117.2 (35.8) min, respectively. We conclude that the time courses of neuromuscular blockade following pipecuronium and pancuronium are similar, despite the differences in Vss and Cl.