ATC vet code: QJ01BA90
Pharmacotherapeutic Group
Antibiotic, member of the phenicol family.
Pharmacodynamic properties
Florfenicol is a broad-spectrum synthetic antibiotic in the phenicol group that is active against most Gram-positive and Gram-negative bacteria isolated from domestic animals. Florfenicol acts by inhibition of protein synthesis at the ribosomal level and is bacteriostatic. However, bactericidal activity has been demonstrated in-vitro against Pasteurella multocida when florfenicol is present at concentrations above the Minimal Inhibitory Concentration (MIC) for 4 to 12 hours.
In-vitro testing has shown that florfenicol is active against the bacterial pathogens most commonly isolated in respiratory diseases in pigs, including P. multocida. A total of 193 P. multocida isolates from the respiratory tract of swine were collected between 2002 and 2003 in France, Spain, Greece, Germany, the United Kingdom and Belgium. The MIC of florfenicol against the target pathogen ranges from 0.25 to 1 µg/ml with a MIC90 of 0.5 µg/ml. The only mechanisms of chloramphenicol resistance that are known to have significant clinical relevance are CAT (Chloramphenicol Acetyl Transferase)-mediated inactivation and efflux-pump resistance. Of these, only some of the efflux mediated resistance would also confer resistance to florfenicol and thus have the potential to be affected by florfenicol use in animals.
Pharmacokinetic properties
After administration to pigs by gavage at 10 mg/kg under experimental conditions, absorption of florfenicol was variable but peak serum concentrations of approximately 5 µg/ml were reached approximately 3 hours after dosing. The terminal half-life was between 3 and 4 hours. When pigs were given free access, for 5 days, to feed medicated with Nuflor Swine Premix at the recommended dose of 10 mg/kg serum florfenicol concentrations exceeds 1 µg/ml for more than 16 hours each day of treatment.
Florfenicol is well absorbed when administered orally and following distribution it is rapidly eliminated in the urine and faeces in a ratio of 3:1. A fraction is excreted unchanged and the rest is metabolised into 5 major metabolites.
After parenteral dosing of florfenicol to pigs, it has been shown that lung concentrations are similar to serum concentrations.