Pharmacokinetics of oxolinic acid in sea-bass, Dicentrarchus labrax (L., 1758), after a single rapid intravascular injection.

The pharmacokinetics of oxolinic acid was studied in sea-bass (Dicentrarchus labrax). The fish were kept in seawater at 15.2 degrees C with a 12 h/12 h photoperiod. Oxolinic acid was injected in the caudal vein of anaesthetized sea-bass in a single rapid intravascular administration at a dose of 10 mg/kg of body weight. Plasma concentrations of oxolinic acid were determined using two analytical methods, a classic plate diffusion bioassay using Escherichia coli and a high performance liquid chromatography (HPLC) using solid phase extraction with an internal standard and a U.V. detection. The mean recoveries were 99.6% and 110.8% and determination limits were 0.04 microg/mL and 0.02 microg/mL, for the bioassay and the HPLC respectively. Compared to other fish species, the oxolinic acid was rapidly (absorption half life, t(a1/2) = 0.69 h) distributed to body tissues outside the blood volume (volume of central compartment, Vc = 0.4 L/kg) and presented a large volume of distribution (Vdss = 2.55 L/kg). Considering its disappearance from the central compartment (rate constant: central-eliminated, k10 = 0.16 h[-1]) and its total body clearance (Cl[t] = 0.066 L/kg x h), the elimination phase of the oxolinic acid in sea-bass was shorter than in trout kept in freshwater, and longer than in salmon in seawater. Consequently, the area under the concentration-time curve (AUC = 157 microg x h/mL) and the mean residence time (MRT = 42 h) were relatively low and short, respectively.