PHARMACOKINETICS OF BENZOCAINE IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)AFTER INTRAARTERIAL DOSING

The pharmacokinetics of benzocaine were analyzed in rainbow trout (Onc orhynchus mykiss) after intraarterial bolus administration of benzocai ne at nominal concentrations of 6 and 9 mg/kg. Distributive phase phar macokinetic parameters were difficult to estimate. Benzocaine concentr ations at 2 min after dosing were highly variable and decreased rapidl y within the first 10 min. Benzocaine concentrations were near or belo w the quantitation limit 90 min after dosing. A three-compartment phar macokinetic model best described benzocaine concentrations in plasma. The apparent volume of distribution at steady state and total body cle arance increased with respect to dose. Since the mean residence time w as similar at both dosages, the differences in the apparent volume of distribution at steady state and total body clearance may have been th e result of data variability or the degree of anaesthesia rather than dose dependency. The model parameters indicated that distribution of b enzocaine outside of the plasma was limited. Despite the initial rapid distribution and elimination of benzocaine from plasma, terminal phas e benzocaine elimination was relatively slow (terminal elimination pha se half-lives of 89 and 109 min).