Pharmacokinetics of Enrofloxacin in Koi Carp (Cyprinus carpio) after Various Routes of Administration

Abstract

The pharmacokinetics of enrofloxacin was studied in koi carp (Cyprinus carpio) after single administration by intraperitoneal (IP) and intramuscular (IM) injection, oral gavage (PO) at a dose of 10 mg/kg body weight and by 5 mg/liter bath for 5 hr at room temperature (27°C). Blood samples were
obtained from caudal vein at 0, 15, 30, 60 min and 2, 8, 24, 48, 72 and 96 hr following administration. Serum antimicrobial concentrations were determined by microbioassay using Bacillus subtilis as an indicator organism where maximal concentrations (Cmax) of drug in plasma were 36.6 ± 21.3, 4.6 ± 2.4, 14.4 ± 7.7 and 0.9 ± 0.3 mg/L after IP, IM, PO and bath at 60, 60, 5 and 5 min, respectively. According to one-compartment pharmacokinetic model, elimination half-life ( T_1/2) were 16.1, 17.9, 16.6 and 42.1 hr, volumes of distribution (Vd) were 0.3, 3.1, 1.5 and 10.4 L/kg, and area under the curve (AUC) were 797.8, 82.7, 156.4 and 29.1 mg-hr/L after IP, IM, PO and bath, respectively. It was found that those 4 routes of enrofloxacin administration to koi were effective since the concentrations of drug in plasma were greater than minimal inhibitory concentration (MIC) of most fish bacterial pathogens.