Pharmacokinetics of enrofloxacin after oral, intramuscular and bath administration in crucian carp (Carassius auratus gibelio)

The pharmacokinetics of enrofloxacin (ENR) was studied in crucian carp (Carassius auratus gibelio) after single administration by intramuscular (IM) injection and oral gavage (PO) at a dose of 10mg/kg body weight and by 5mg/L bath for 5hr at 25 degrees C. The plasma concentrations of ENR and ciprofloxacin (CIP) were determined by HPLC. Pharmacokinetic parameters were calculated based on mean ENR or CIP concentrations using WinNonlin 6.1 software. After IM, PO and bath administration, the maximum plasma concentration (C-max) of 2.29, 3.24 and 0.36g/ml was obtained at 4.08, 0.68 and 0hr, respectively; the elimination half-life (T-1/2) was 80.95, 62.17 and 61.15hr, respectively; the area under the concentration-time curve (AUC) values were 223.46, 162.72 and 14.91ghr/ml, respectively. CIP, an active metabolite of enrofloxacin, was detected and measured after all methods of drug administration except bath. It is possible and practical to obtain therapeutic blood concentrations of enrofloxacin in the crucian carp using IM, PO and bath immersion administration.