ATCVet code: QJ01BA90.
Pharmacotherapeutic group
Antibacterial for systemic use (Amphenicols).
Pharmacodynamic properties
Florfenicol is a synthetic broad spectrum antibiotic effective against most Gram-positive and Gram-negative bacteria isolated from domestic animals. Florfenicol acts by inhibiting protein synthesis at the ribosomal level and is bacteriostatic. Laboratory tests have shown that florfenicol is active against the most commonly isolated bacterial pathogens involved in ovine and bovine respiratory disease which include M. haemolytica, P. multocida, and, for cattle H. somni. Florfenicol is considered to be a bacteriostatic agent, but in vitro studies of florfenicol demonstrate bactericidal activity against M. haemolytica, P. multocida and H. somni.
MIC data for the target pathogens are presented in the table below:
Species | Range (µg/ml) | MIC50 (µg/ml) | MIC90 (µg/ml) |
M. haemolytica (n=151) | 0.25-2 | 1 | 1 |
P. multocida (n=88) | 0.25-0.5 | 0.5 | 0.5 |
Strains were isolated from sheep suffering from respiratory tract infection in Germany, United Kingdom, Spain and France between 2006 and 2010.
Pharmacokinetic properties
Cattle:
Intramuscular administration at the recommended dose of 20 mg/kg maintains efficacious blood levels in cattle for 48 hours. Maximum mean serum concentration (Cmax) of 3.37 µg/ml occurs at 3.3 hours (tmax) after dosing.
The mean serum concentration 24 hours after dosing was 0.77 µg/ml.
Subcutaneous administration at the recommended dose of 40 mg/kg maintains efficacious blood levels in cattle (ie above the MIC90 of the main respiratory pathogens) for 63 hours. Maximum serum concentration (Cmax) of approximately 5 µg/ml occurs approximately 5.3 hours (tmax) after dosing. The mean serum concentration 24 hours after dosing is approximately 2 µg/ml.
The harmonic mean elimination half-life was 18.3 hours.
Sheep:
After initial intramuscular administration of florfenicol (20 mg/kg), the mean maximum serum concentration of 10.0 μg/ml is reached after 1 hour. Following the third intramuscular administration, the maximum serum concentration of 11.3 μg/ml is reached after 1.5 hours. The elimination half-life was estimated to be 13.76 + 6.42h. Bioavailability is about 90 %.