Pharmacokinetic and pharmacodynamic profiles of danofloxacin administered by two dosing regimens in calves infected with Mannheimia (Pasteurella) haemolytica

The pharmacokinetics and pharmacodynamics of danofloxacin in calves with induced Mannheimia (Pasteurella) haemolytica pneumonia were evaluated. Calves received either saline as an intravenous (IV) bolus or danofloxacin (0.738 mg/kg of body weight) administered as either a single IV bolus or a 36-h continuous IV infusion. Blood samples and bronchial secretions were collected before and at predetermined times over 48 h following the start of treatment. Calves were assessed clinically throughout, and lung consolidation was assessed at necropsy. Bronchial secretions and lung tissue were cultured for M. haemolytica. Bolus administration of danofloxacin produced a high maximum drug concentration-to-MIC ratio (Cmax:MIC) of 14.5 and a time period of 9.1 h when plasma danofloxacin concentrations exceeded the MIC (T>MIC). Following danofloxacin infusion, the Cmax:MIC was low (2.3), with a long T>MIC (33.3 h). The area under the curve-to-MIC ratios were 43.3 and 49.1 for the bolus and infusion administrations, respectively. The single bolus of danofloxacin was more effective than the same dose administered by continuous infusion, as indicated by a significantly lower (P < 0.05) number of animals with M. haemolytica in bronchial secretions after treatment and lower rectal temperatures in the 24 h after the start of treatment. Thus, danofloxacin exhibited concentration-dependent antimicrobial activity in cattle with respiratory disease caused by M. haemolytica.