Antibacterials for systemic use, Amphenicols,
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. Laboratory tests have 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.
Florfenicol is considered to be a bacteriostatic agent, but in vitro studies of florfenicol demonstrated bactericidal activity against 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 been identified in the target pathogens Pasteurella multocida and Mannhemia haemolytica. Cross resistance with chloramphenicol can occur. Resistance to florfenicol and other antimicrobials has been identified in the food-borne pathogen Salmonella typhimurium. Co-resistance with the third-generation cephalosporins has been observed in respiratory and digestive Escherichia coli.
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. The harmonic mean elimination half life was 18.8 hours.
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.