Pharmacokinetics and tissue distribution of oxolinic acid in Nile tilapia Oreochromis niloticus following a single oral gavage under tropical conditions

ABSTRACT The pharmacokinetic properties of oxolinic acid (OA) were investigated after a single oral gavage at 12 mg/kg biomass in adult Nile tilapia, Oreochromis niloticus, at 24.10–32.20°C. Drug residue analysis was conducted at 14 time points across eight tissues, with three fish sampled per time point from triplicate tanks by LC-MS/MS. The drug kinetics were consistent with a two-compartment model, with maximum concentrations observed in each organ and in plasma exceeding the minimum inhibitory concentration (MIC) of OA. The time to peak (T max ) in plasma (16.74 h) illustrated that OA was absorbed comparatively faster. The organs' T max values indicated a distribution of OA within 8-16 h, except for the liver (4.38 h) and kidney (2.71 h). The results suggested an early uptake in the liver and kidney. The elimination half-life of OA was longer in the liver, muscle, kidney, gill, and bile, suggesting hepatic-biliary elimination, renal excretion, and branchial elimination as significant elimination routes of OA in O. niloticus. Our observations of OA accumulation exceeding the MIC in plasma and other tested organs suggested potential therapeutic activity against OA-susceptible bacterial strains. The C max /MIC and AUC 0-24 /MIC ratios against the tested pathogens indicated that therapeutic efficacy was limited to strains with MIC values ≤0.39 µg/mL. The comparatively shorter plasma T max observed in O. niloticus relative to temperate fish (T max 21–24 h) suggested a temperature-driven enhancement of OA absorption and elimination kinetics.