Pharmacokinetic study of enrofloxacin in Nile tilapia (Oreochromis niloticus) after a single oral administration in medicated feed

The objective of this study was to evaluate the disposition kinetics of enrofloxacin (ENR) in the plasma and its distribution in the muscle tissue of Nile tilapia (Oreochromis niloticus) after a single oral dose of 10mg/kg body weight via medicated feed. The fish were kept at a temperature between 28 and 30 degrees C. The collection period was between 30min and 120h after administration of the drug. The samples were analyzed by high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). The ENR was slowly absorbed and eliminated from the plasma (C-max = 1.24 +/- 0.37 g/mL; T-max =8h; T-1/2Ke=19.36h). ENR was efficiently distributed in the muscle tissue and reached maximum values (2.17 +/- 0.74g/g) after 8h. Its metabolite, ciprofloxacin (CIP), was detected and quantified in the plasma (0.004 +/- 0.005g/mL) and muscle (0.01 +/- 0.011g/g) for up to 48h. After oral administration, the mean concentration of ENR in the plasma was well above the minimum inhibitory concentrations (MIC50) for most bacteria already isolated from fish except for Streptococcus spp. This way the dose used in this study allowed for concentrations in the blood to treat the diseases of tilapia.