Pharmacokinetics of florfenicol and its metabolite florfenicol amine in crucian carp (Carassius auratus) at three temperatures after single oral administration

The pharmacokinetic profiles of florfenicol (FF) and florfenicol amine (FFA) following a single oral dose of FF at 10 mg.kg(-1) body weight were compared in crucian carp reared at three different temperatures of fresh water. The concentrations of FF and FFA were determined simultaneously by high-performance liquid chromatography coupled with fluorescence detection, followed by compartmental analysis using a one-compartment open model. At water temperatures of 10 +/- 0.5, 20 +/- 0.5, and 25 +/- 0.5 degrees C, the maximum concentration (C-max) of FF was 2.435, 2.795, and 3.555 mu g.mL(-1), respectively, while that of FFA was 0.810, 0.945, and 1.063 mu g.L-1, respectively. The absorption half-life (t(1/2ka)) of FF was 0.72, 0.73, and 0.70 h, and the elimination half-life (t(1/2kel)) was 22.86 12.29, and 9.56 h, respectively. The volume of distribution per fraction absorbed (V-d/F) for FF at water temperatures of 10, 20, and 25 degrees C was 3.67, 2.99, and 2.29 L.kg(-1), respectively. For FFA, the formation half-life (t(1/2kf)) was 2.13, 3.47, and 5.11 h, respectively, whereas the t(1/2kel) was 27.79, 20.33, and 15.44 h at water temperatures of 10, 20, and 25 degrees C, respectively. At higher water temperatures, FF was absorbed and eliminated more quickly and was more extensively distributed than at lower water temperatures; in addition, the formation and elimination of FFA were faster at higher water temperatures. From the values of time > minimum inhibitory concentration (T > MIC) calculated in the current study at 10 degrees C, an oral dose of FF at 10 mg.kg(-1) body weight administered at 48-h intervals would be sufficient for the treatment of bacterial infection with an MIC of <= 0.5 mu g.L-1, whereas a 24-h interval would be necessary at 20 and 25 degrees C to treat bacterial infections with the same MIC.