Single‐dose pharmacokinetics of flumequine in halibut (Hippoglossus hippoglossus) and turbot (Scophthalmus maximus)

Flumequine was administered to halibut (Hippoglossus hippoglossus) and turbot (Scophthalmus maximus) intravenously (i.v.) and orally (p.o.) at a dose of 10 mg/ kg bodyweight, and as a bath-treatment at a dose of 10 mg/L water for 2 h, using identical experimental designs. The study was performed in seawater with a salinity of 3% and a temperature of 10.3+/-0.4 degrees C (halibut) and 18.0+/-0.3 degrees C (turbot). Pharmacokinetic modelling of the data showed that flumequine had quite similar pharmacokinetic properties in halibut and turbot. Following intravenous administration, the volumes of distribution at steady state (Vss) were 2.99 L/kg (halibut) and 3.75 L/kg (turbot). Plasma clearances (Cl) were 0.12 L/kg (halibut) and 0.17 L/h x kg (turbot) and the elimination half-lives (t(1/2lambdaz)) were calculated to be 32 h (halibut) and 34 h (turbot). Mean residence times (MRT) were 25.1 h (halibut) and 22.2 h (turbot). Following oral administration, the t(1/2lambdaz) were 43 h (halibut) and 42 h (turbot). Maximal plasma concentrations (tmax) were 1.4 mg/L (halibut) and 1.9 mg/L (turbot), and were observed 7 h post administration in both species. The oral bioavailabilities (F) were calculated to 56% (halibut) and 59% (turbot). Following bath administration maximal plasma concentrations were 0.08 mg/L (halibut) and 0.14 mg/ L (turbot), and were observed 0 h (halibut) and 3 h (turbot) after the end of the bath. The bioavailability in halibut following a 2-h bath treatment was 5%.