Pharmacokinetics of florfenicol and its major metabolite, florfenicol amine, in rabbits

The pharmacokinetics of florfenicol and its active metabolite florfenicol amine were investigated in rabbits after a single intravenous (i.v.) and oral (p.o.) administration of florfenicol at 20 mg/kg bodyweight. The plasma concentrations of florfenicol and florfenicol amine were determined simultaneously by an LC/MS method. After i.v. injection, the terminal half‐life ( t 1/2 λ z ), steady‐state volume of distribution, total body clearance and mean residence time of florfenicol were 0.90 ± 0.20 h, 0.94 ± 0.19 L/kg, 0.63 ± 0.06 L/h/kg and 1.50 ± 0.34 h respectively. The peak concentrations ( C max ) of florfenicol (7.96 ± 2.75  μ g/mL) after p.o. administration were observed at 0.90 ± 0.38 h. The t 1/2 λ z and p.o. bioavailability of florfenicol were 1.42 ± 0.56 h and 76.23 ± 12.02% respectively. Florfenicol amine was detected in all rabbits after i.v. and p.o. administration. After i.v. and p.o. administration of florfenicol, the observed C max values of florfenicol amine (5.06 ± 1.79 and 3.38 ± 0.97  μ g/mL) were reached at 0.88 ± 0.78 and 2.10 ± 1.08 h respectively. Florfenicol amine was eliminated with an elimination half‐life of 1.84 ± 0.17 and 2.35 ± 0.94 h after i.v. and p.o. administration respectively.