Tissue distribution and elimination of florfenicol in tilapia (Oreochromis niloticus × O. caureus) after a single oral administration in freshwater and seawater at 28 °C

Tissue distribution and elimination of florfenicol in seawater-acclimated tilapia were compared with those in freshwater tilapia at 28 °C after they were given a single oral dose of 10 mg/kg body weight (b.w.). In most sampling time points, the concentrations of florfenicol in the tissues (muscle, liver, kidney, gill and bile) in freshwater tilapia were higher than those in seawater tilapia. In the major elimination phase the elimination half-lives (T1/2β) in all the tissues (except for bile) of freshwater tilapia were longer than those in seawater tilapia. These findings indicated that the distribution level of florfenicol in freshwater tilapia was higher than that in seawater tilapia and the elimination of florfenicol in seawater tilapia was more rapid than that in freshwater tilapia. The main excretion pathway (gill excretion) of the drug in seawater-acclimated tilapia was different from that (bile excretion) in freshwater tilapia, which should be responsible for the considerable difference in pharmacokinetics from freshwater tilapia.