Pharmacokinetics and tolerance of florfenicol in Equidae

Florfenicol was administered to horses and ponies at a dose rate of 22 mg/kg bwt by i.v., i.m. and oral routes. Following i.v. administration it had an elimination half-life of 1.8 +/- 0.9 h, a body clearance of 0.4 +/- 0.1 l/h.kg and a volume of distribution at steady-state of 0.7 +/- 0.2 l/kg. It was highly bioavailable following i.m. (81%) and oral (83%) administration. Less than 15% of the administered dose was excreted unchanged in the urine during the 30 h following administration. Animals treated with florfenicol had elevated bilirubin concentrations. Florfenicol was well tolerated by animals in the present study although all animals had loose faeces following administration by each route. At present, florfenicol cannot be recommended for clinical use until multiple dose studies have been carried out to confirm its safety.