Bacterial disease is a critical issue in aquaculture industry, and antimicrobials remain the key to ensure food safety. The usage of antimicrobials for aquatic animals should consider the influence of rearing temperature because their pharmacokinetics (PK) is temperature-dependent. Through pharmacokinetic-pharmacodynamic (PK-PD) approach, we investigated the optimal dosing regimens of florfenicol (FF) at multiple minimum inhibitory concentration (MIC) levels in seabass rearing at both 25 °C and 30 °C.
The serum concentrations of FF versus time after a single oral administration (10 mg/kg, PO) at 2 rearing temperatures were shown in Figure 1. The corresponding PK parameters indicated that rearing at 30 °C resulted in longer absorption half-life, shorter elimination half-life, faster clearance, lower apparent volume of distribution and smaller area under the serum concentration-time curve than at 25 °C (Table 1). The optimal dosages were then calculated with related PK parameters using equation for multiple-dose extravascular administration. A 1.5-2.0 fold differences in dosage between 2 rearing temperatures (Table 2) at each MIC level were evident. Our results demonstrated that at the common recommended dose of 10-15 mg/kg/day, it was likely under-dosed especially in warmer rearing temperature, which might cause ineffective medication. Whether or not non-linear PK occurs at higher dosage as was discovered for Nile Tilapia warrants further study.