Population Pharmacokinetics of Enrofloxacin in Ctenopharyngodon idella Based on the Sparse Sampling Method and a Nonlinear Mixed Effect Model Following Intravenous and Oral Administration

The objective of this study was to implement population pharmacokinetic (PPK) of enrofloxacin (EF) in grass carp (Ctenopharyngodon idella) after a single oral administration and a single intravenous administration based on a nonlinear mixed effect model. The plasma samples collected by the sparse sampling method were detected by high-performance liquid chromatography with a fluorescent detector. The initial pharmacokinetic (PK) parameters were evaluated by reference search and the calculation of a na & iuml;ve pooled method. After oral administration, the concentration-time profile was best described by a one-compartment open model. The absorption rate constant (Ka), apparent distribution volume (V), and systemic clearance (CL) were estimated to be 3.11/h, 4.36 L/kg, and 0.079 L/h/kg, respectively. After intravenous administration, the concentration-time curve was best simulated by a two-compartment open model. The apparent distribution volume of the central compartment (V1), apparent distribution volume of the peripheral compartment (V2), CL, and clearance from the central compartment to the peripheral compartment (CL2) were estimated to be 0.42, 2.05 L/kg, 0.067, and 2.94 L/h/kg, respectively. Finally, the bioavailability was calculated to be 84.81%. The parameter of AUC/minimum inhibitory concentration value was estimated to be more than 506.32 for Aeromonas hydrophila, Aeromonas sobria, and Flavobacterium columnare indicating that EF at 20 mg/kg has high effectiveness for these pathogens. This study supported a concise method for conducting PK study in aquatic animals that facilitated the development of PK methodology in aquaculture.