Pharmacokinetics and bioavailability of oxytetracycline in gilthead sea bream (Sparus aurata) after a single dose

This is the first study to investigate the pharmacokinetic parameters of oxytetracycline (OTC) in gilthead sea bream (Sparus aurata). Following a single intravascular injection of OTC (40 mg/kg) in 100 g fish kept at 20 degreesC, the distribution half-life (t(1/2alpha)) and the elimination half-life (t(1/2beta)) of OTC were found to be long (2 and 53 h, respectively). The drug was well distributed throughout the internal body compartments since the apparent volume of distribution of the drug at steady-state (V-d(ss)) and the apparent volume of distribution by the area method (V-d(area)) were found to be high (2.9 and 3.8 l/kg, respectively). OTC had a long mean residence time (MRT) (56 h) but a short total clearance (CLT) (0.05 l/kg h). The slow elimination of the drug suggests a need for long withdrawal periods prior to use of dosed fish for human consumption. Although the bioavailability (F%) of OTC following oral administration in aqueous suspension (75 mg/kg) was calculated to be low (9%), maximum OTC plasma concentration was relatively high (2.5 mug/ml), indicating that current therapeutic regimens applied to gilthead sea bream might be effective against bacterial pathogens. (C) 2003 Elsevier Science B.V. All rights reserved.