Analytical model of some pharmacokinetic and pharmacodynamic properties of fazadinium in man.

The neuromuscular blocking characteristics and plasma concentration decay of fazadinium bromide, a short acting, non-depolarizing muscular relaxant, were simultaneously observed under standardised conditions in 6 healthy, anaesthetized, adult patients. The results were analyzed by a new pharmacodynamic model, which takes into account certain relationships describing the binding of non-depolarizing neuromuscular blocking agents and the postsynaptic receptor occupation ratio. According to the simultaneous performed, the pharmacodynamic parameters determined: KB-apparent value of equilibrium constant of fazadinium--receptors exchange (mean +/- SEM) 0.404 + 0.045 mumol/l, and the value of postsynaptic occupation ratio for 50% paralysis of 0.89 +/- 0.004 were in agreement with values reported in the literature for mammalian neuromuscular junctions in vitro. The apparent validity of the pharmacodynamic model and its value is simulating dose/effect relationships of non-depolarizing neuromuscular blocking agents are discussed and illustrated.