Pharmacokinetics of florfenicol in tilapia at two water temperatures

The pharmacokinetics of florfenicol in tilapia (Oreochromis niloticus×O.aureus) was studied in fresh water at 22℃ and 28℃.The tilapia were forced-fed with medicated feed containing a single dose of 10 mg · kg^-1 bodyweight of florfenicol. The peak drug concentrations (C_max), the time to the peak drug concentration (T_max), the elimination half-lives (T_1/2β) and the area under the concentration-time curve (AUC) in plasma were 4.46μg · mL^-1, 12 h, 10.03 h and 86.68 h · μg · mL^-1, respectively, at 22℃ and 3.90 μg · mL^-1, 12 h, 8.12 h and 72.44 h · μg · mL^-1, respectively, at 28℃. Corresponding C_max, T_max, T_1/2β and AUC values in muscle were 6.88 μg · g^-1, 12 h, 10.97 h and 112.71 h · μg · g^-1, respectively at 22℃ and 4.59 μg · g^-1, 12 h, 8.03 h and 73.66 h · μg · g^-1, respectively, at 28℃. The elimination half-lives were longer at the lower water temperature than those at the higher water temperature, with the margin of 1.91 h in plasma and 2.96 h in muscle, respectively, which indicated that the drug was eliminated more rapidly at the higher water temperature than those at the lower water temperature. Although the same T_max in plasma or muscle at both water temperatures were observed, however, the C_max and AUC were lower in tilapia at the higher water temperature than those at the lower water temperature, indicating the better absorption and availability of florfenicol at the lower water temperature than at the higher water temperature.