Abstract:The aim of this study was to evaluate the pharmacokinetics of florfenicol (FF) and its metabolite,florfenicol amine (FFA),after oral (p.o.) administration and investigate their depletion after multiple oral administrations for 3 consecutive days in rice field eel ( Monopterus albus ) at 25℃.After p.o.administration of 20 mg/kg,the peak concentration of FF ( C max) and time to reach FF peak concentration ( T max) in plasma,liver,kidney and muscle were 6.07 mg/L,7.57 mg/kg,9.34 mg/kg,5.87 μg/mg and 3.67 h,4.45 h,2.01 h,9.28 h,respectively.The order of t 1/2β was kidney (29.26 h)>liver (19.32 h)>muscle (17.22 h)>plasma (10.84 h).FFA was also found in all tissues with a lower concentration than FF after p.o.administrations throughout the study.The longest t 1/2β of 45.93 h and the largest metabolic rate (MR) of 49.21% were observed in kidney.After multiple oral doses (20 mg/(kg·d) for 3 d),the highest residues was observed in kidney,next in liver and then in muscle.The residues was undetectable in all tissues after 10 d which was similar to the former 12 d withdrawal time to ensure that the residues of florfenicol are less than the maximal residue limit of tolerance established by Japan.