Pharmacokinetics of a discontinuous absorption process of oxolinic acid in turbot, Scophthalmus maximus, after a single oral administration

1. The pharmacokinetics of oxolinic acid have been studied in 500 g turbot (Scophthalmus maximus). The fish were kept in seawater at 16 degrees C with a 15 h/9 h photoperiod. Oxolinic acid was administered orally via a stomach tube at a single dose of 10 mg/kg of body weight. Serum concentrations of oxolinic acid were determined by a (HPLC) using liquid phase extraction with an internal standard and a fluorescence detection. 2. The pharmacokinetic process was not significantly sex-influenced. The short elimination phase of the oxolinic acid in turbot after oral administration was similar to the elimination after intravascular administration. The serum concentration profile of oxolinic acid was better described by a discontinuous absorption model than by compartment models using continuous absorption processes. The absorption of oxolinic acid in turbot was characterized by two distinct phases after a lag time of about 2 h. A time (Tmax) of 12 h was necessary to reach the peak serum concentration (Cmax) of 1.41 microg/ml. The oral bioavailability was 27.9%. 3. Based on the minimum inhibitory concentration for susceptible strains, and especially Vibrio anguillarum, the oxolinic acid could be effective in turbot after an oral treatment of 10 mg/kg/day.