Pharmacokinetics of florfenicol in cod Gadus morhua and in vitro antibacterial activity against Vibrio anguillarum

The pharmacokinetic profile of the antibacterial agent florfenicol was studied in plasma after intravenous (i.v.) injection and in plasma, muscle and liver following oral (p.o.) administration to cod Gadus morhua, held in seawater at 8 degrees C and weighing 100 to 200 g. Following i.v. injection, the plasma drug concentration-time profile showed 2 distinct phases. The plasma distribution half-life (t1/2alpha) was estimated to be 1.6 h, the elimination half-life (t1/2beta) to be 43 h, the total body clearance (ClT) to be 0.015 1 kg(-1) h(-1) and mean residence time (MRT) to be 74 h. The volume of distribution at steady state, Vd(ss), was calculated to be 1.1 l kg(-1). Following p.o. administration, the bioavailability was estimated to be 91%, the peak plasma concentrations (Cmax) to be 10.8 microg ml(-1) and the time to peak plasma concentrations (Tmax) to be 7 h. Corresponding Cmax and Tmax values were 13.0 microg g(-1) and 9 h, respectively, in muscle and 12.1 microg g(-1) and 9 h, respectively, in liver. The in vitro minimum inhibitory concentration (MIC) values of florfenicol against 3 Vibrio anguillarum strains isolated from diseased cod (A-21, HI-610, HI-618) were 0.5 microg ml(-1) for all 3 strains.