Clinical pharmacokinetics of pancuronium bromide

Plasma concentrations of pancuronium bromide have been studied in seven surgical patients following a 6 mg intravenous bolus injection of the drug for neuromuscular blockade. Concurrently, evoked muscle twitch response was monitored for each patient as a measure of the pharmacodynamic effect of the drug. The plasma decay curve for pancuronium was found to be biphasic and after rigorous statistical analysis the data were interpreted according to a 2-compartment open model. The half-life of the beta-phase varied between 89.5 and 161.5 min. The apparent volume of distribution of the central compartment ranged from 62.9 to145.5 ml/kg and the plasma clearance from 57.6 to 187.3 ml/min. At the first sign of recovery from neuro-muscular blockade the mean pancuronium plasma level was found to be 0.218 mcg/ml. The mean duration of action as measured from time of onset of paralysis to 20% recovery was 83.4 min with the plasma level at 20% being 0.169 mcg/ml corresponding to 45.4% of dose remaining to be eliminated from the body.