Pharmacokinetics of florfenicol and its metabolite, florfenicol amine, in dogs

A study on the bioavailability and pharmacokinetics of florfenicol was conducted in six healthy dogs following a single intravenous (i.v.) or oral (p.o.) dose of 20 mg kg−1 body weight (b.w.). Florfenicol concentrations in serum were determined by a high-performance liquid chromatography/mass spectrometry. Plasma concentration–time data after p.o. or i.v. administration were analyzed by a non-compartmental analysis. Following i.v. injection, the total body clearance was 1.03 (0.49) L kg−1 h−1 and the volume of distribution at steady-state was 1.45 (0.82) L kg−1. Florfenicol was rapidly distributed and eliminated following i.v. injection with 1.11 (0.94) h of the elimination half-life. After oral administration, the calculated mean Cmax values (6.18 μg ml−1) were reached at 0.94 h in dogs. The elimination half-life of florfenicol was 1.24 (0.64) h and the absolute bioavailability (F) was achieved 95.43 (11.60)% after oral administration of florfenicol. Florfenicol amine, the major metabolite of florfenicol, was detected in all dogs after i.v. and p.o. administrations.