metadata toggle
Pharmacological particulars
Pharmacotherapeutic group: Antibacterials for systemic use, amphenicols
ATC Vet Code: QJ01BA90
Pharmacodynamic properties
Florfenicol is a synthetic, broad-spectrum antibiotic in the phenicol group active against most Gram-positive and Gram-negative organisms isolated from domestic animals. Florfenicol acts by inhibiting protein synthesis at the ribosomal level and is bacteriostatic. However, bactericidal activity has been demonstrated in-vitro against Actinobacillus pleuropneumoniae and Pasteurella multocida when florfenicol is present at concentrations above the MIC for up 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 Actinobacillus pleuropneumoniae and Pasteurella multocida. The MIC50 and MIC90 values for Actinobacillus pleuropneumoniae were 0.5 µg/ml and 0.5µg/ml. The MIC50 and MIC90 values for Pasteurella multocida were 0.5 µg/ml and 1µg/ml. These strains were isolated from European countries during 2015-2016. Observed resistance was low based on the clinical breakpoints (CLSI): sensitive ≤ 2 µg/ml, intermediate 4 µg/ml and resistant ≥ 8 µg/ml. Resistance to florfenicol mainly comes from the presence of specific (e.g. FloR) or multi-substance (e.g. AcrAB-TolC) efflux pumps. The genes corresponding to these mechanisms are coded on genetic elements such as plasmids, transposons or gene cassettes. Cross resistance with chloramphenicol is possible.
Pharmacokinetic properties
After administration to pigs by gavage at 15 mg/kg under experimental conditions, absorption of florfenicol was variable but peak serum concentrations of approximately 5 μg/mL were reached approximately 2 hours after dosing. The terminal half-life was between 2 and 3 hours. When pigs were given free access, for 5 days, to water medicated with 100 mg florfenicol per litre of water, serum concentrations of florfenicol exceeded 1 μg/mL for the entire 5 day treatment period except for a couple of short excursions below 1 μg/mL. After absorption and distribution, florfenicol is extensively metabolised by pigs and rapidly eliminated, primarily in urine. After parenteral dosing of florfenicol to pigs, it has been shown that lung concentrations are similar to serum concentrations.
Environmental properties
Manure from treated animals may be harmful to terrestrial plants.