Relationship of the serum concentration of pancuronium to its neuromuscular activity in man

The relationship between the time course of the decay of serum concentrations of pancuronium and its neuromuscular blocking effect has been investigated after the intravenous administration of 50, 80 and 100 microgram/kg doses to anesthetized patients. Following administration of these doses, maximal neuromuscular block in the adductor pollicis muscle developed in about 7, 2.5, and 2 minutes and lasted about 20, 40, and 60 minutes, respectively. The times from start of recovery to return of twitch tension to 25, 50, and 75 per cent of control were similar in the different dosage groups, but occurred progressively later with increasing doses. At times of 25, 50, and 75 per cent recovery mean serum concentrations (pooled values) were 0.13 +/- 0.01,0.11 +/- 0.01, and 0.10 +/- 0.01 microgram/ml (+/- SEM), respectively. Neuromuscular transmission to the adductor pollicis muscle started to recover at a mean serum pancuronium concentration of 0.21 +/- 0.03 microgram/ml. The data obtained in this study are in agreement with the experimental and clinical findings of similar studies with d-tubocurarine, and indicate that there is a correlation between the serum concentrations of muscle relaxants and the intensity of their neuromuscular activities.