Tissue distribution and residue depletion of oxolinic acid in gilthead sea bream (Sparus aurata) and sharpsnout sea bream (Diplodus puntazzo) following multiple in-feed dosing

Abstract

Abstract The tissue distribution and residue depletion of oxolinic acid (OA) were investigated in gilthead sea bream and sharpsnout sea bream after a multiple (10 days) in-feed administration (30 mg/kg fish) at 19 °C. Plasma, muscle, skin, liver and bile were sampled daily during treatment (1–10 days) and post-treatment (11,12, 14, 15 and 17 days) and subsequently analysed for OA concentrations using high-performance liquid chromatography and fluorescent detection (HPLC-SFD). Oxolinic acid displayed biphasic elimination in tissues of both species during treatment and reached “consumer safe levels” 24 h after treatment. OA concentration in gilthead sea bream peaked on day 4, with highest concentrations in liver (2660 ng/g), followed by bile (2370 ng/ml), skin (2350 ng/g), muscle (1330 ng/g) and plasma (880 ng/ml). In sharpsnout sea bream, peaked OA concentrations were observed in liver (2720 ng/g) on day 4, while highest concentrations were measured later on day 5 in plasma (910 ng/ml) and day 6 in bile (2360 ng/ml), skin (1960 ng/g) and muscle (1770 ng/g). The calculated areas under the concentration curves (AUC) also reflect a good tissue distribution of OA. Elimination half-lives (t1/2) were estimated to be 11–14 and 11–19 h in tissues of gilthead sea bream and sharpsnout sea bream, respectively. Multiple dosing of OA in sparids should be adequate to confront bacterial pathogens considering published minimum inhibitory concentrations of the drug.