RELATIONSHIP BETWEEN DECAY OF PLASMA CONCENTRATION OF FAZADINIUM AND RECOVERY FROM ITS NEUROMUSCULAR BLOCKING EFFECT

The relationship of the time-course of the decay of plasma concentrationof fazadinium and neuromuscular block has been investigatedafter i.v. administration ofO.75mgkg^–1 to six anaesthetizcdpatients. The phar acokinctic of fazadinium were analysed accordingto a two-compartment open model. A significant correlation wasfound between the plasma concentration of fazadinium and thetwitch height (TH) values during recovery from the block (P<0.001). The mean total plasma concentrations for 25,50and75%THrecoverywere: 1.90±0.17; 1.44±0.l8and 1.08±0.l2µgm^–1,respectivcly.Elapsed time between fazadinium administrationand the Th recovery to 50% (0-TH and the recovery period TH_25–75were 47±4mm and 25±2mm, respectively. Plasma logdecay rate of fazadinium during TH_25–75 period (K_{app 25–75})was: 0.0249±0.0032min^–1. Significant correlations(P<0.01) were observed between the elimination rate constant(k₁₀ ) of the pharmacokinetic model, K_{app 25 –75} (P<0.01)and the pharmacodynamic parameters: time interval 0-TH₅₀ andrecovery rate TH _25-73. These results showed that part of theindividual pharmacodynamic variation had its origin in the interindividualpharmacokinenc variation.