Alcuronium kinetics and plasma concentration-effect relationship.

The kinetics and dynamics of the neuromuscular blocker alcuronium were investigated in 12 surgical patients who received bolus and infusion regimens. In six patients the duration of the infusion was sufficiently long so that a steady-state alcuronium plasma concentration was reached (mean SD, 0.80 +/- 0.23 micrograms/ml). In the remaining six patients a steady state was not reached but the alcuronium concentration at the end of the infusion was 0.91 +/- 0.39 micrograms/ml. Alcuronium kinetic parameters did not differ between the two groups or from those obtained previously after bolus doses. In six patients for whom sufficient alcuronium concentration-time response data were available over the 0 to 100% response range, various mathematic models were used to characterize the concentration-effect relationship. A dynamic model incorporating a separate effect compartment connected to the central compartment was found to be the most appropriate. The (mean +/- SD) rate constant for equilibration of alcuronium concentration and effect was found to be 0.24 +/- 0.11 min-1, whereas the steady-state concentration required to induce 95% paralysis was 0.91 +/- 0.35 micrograms/ml (mean +/- SD).