Pharmacotherapeutic group: Antibacterials for systemic use ATCVet Code: QJ01BA90

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. However, bactericidal activity has been demonstrated in-vitro against Actinobacillus pleuropneumoniae, Pasteurella multocida, Mannheimia haemolytica and Histophilus somni.

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. Laboratory tests have also shown that florfenicol is active against the most commonly isolated bacterial pathogens involved in bovine respiratory disease which include Mannheimia haemolytica, Pasteurella multocida and Histophilus somni.

Acquired resistance to florfenicol is mediated by efflux pump resistance associated with a floR gene. Such resistance has not yet been identified in the target pathogens except for Pasteurella multocida. Cross resistance with chloramphenicol can occur.

Resistance to florfenicol and other antimicrobials has been identified in the food-borne pathogen Salmonella typhimurium.

Swine:

After single intramuscular administration of the recommended dose of 15mg/kg to pigs maximum mean plasma concentration (Cmax) of 2.8 μg/ml occurs at 2 hours (Tmax) after dosing.

After administration to pigs by the intramuscular route, florfenicol is rapidly excreted, primarily in urine. Florfenicol is extensively metabolised.

Cattle:

Intramuscular administration at the recommended dose of 20 mg/kg maintains efficacious blood levels in cattle for 48 hours. Maximum mean plasma concentration (Cmax) of 3.86 μg/ml occurs at 5 hours (Tmax) after dosing. The mean plasma concentration 24 hours after dosing was 1.56 μg/ml.

After subcutaneous administration of the recommended dose of 40 mg florfenicol/kg b.w., maximum plasma concentration (Cmax) of approximately 3.5 μg/ml occurs approximately 7.0 hours (Tmax) after dosing. The mean plasma concentration 24 hours after dosing is approximately 2 μg/ml.

The harmonic mean elimination half life was 18.8 hours.