Single-dose pharmacokinetics of flumequine in the eel (Anguilla anguilla) after intravascular, oral and bath administration

Knowledge of the pharmacokinetic properties of drugs to combat bacterial infections in the European eel (Anguilla anguilla) is limited. One antimicrobial agent likely to be effective is flumequine. The aim of this study was to investigate the pharmacokinetic properties of flumequine in European eels in fresh water. Flumequine was administered to eels (Anguilla anguilla) intravenously (i.v.) and orally (p.o.) at a dose of 10 mg/kg body weight, and as a bath treatment at a dose of 10 mg/L water for 2 h. The study was performed in fresh water with a temperature of 23 + 0.3 degrees C, pH 7.15. Identical experimental designs were used. Two additional bath treatments were also performed, one in which the pH in the water was lowered by approximately 1 unit to 6.07 (dose: 10 mg/L) and one at a dose of 40 mg/L for 2 h in a full-scale treatment. Following i.v. administration, the volume of distribution at steady state was 3.4 L/kg. Total body clearance was 0.012 L/h per kg and the elimination half-life (t1/2lambda z) was calculated to be 314 h. Mean residence time was 283 h. Following oral administration, the t1/2lambda z was 208 h. Maximal plasma concentration (Cmax) was 9.3 mg/L, at 7 h after administration (Cmax). The oral bioavailability (F) was calculated to be 85%. Following bath administration in 10 mg/L for 2 h, maximal plasma concentration was 2.1 mg/L, observed immediately after the end of the bath. The 'bioavailability' in eel following a 2-h bath treatment was 19.8%. Reducing the pH in the bath to 6.07 produced a maximal plasma concentration of 5.5 mg/L, observed immediately after the end of the bath. The 'bioavailability' was increased to 41% by the lowering of the pH. A similar effect was observed in a full-scale treatment (1 kg eels/L water). The CO2 produced by the eel lowered the pH and increased 'bioavailability' to 35%.