Pharmacokinetic-pharmacodynamic integration of danofloxacin after intravenous, intramuscular and subcutaneous administration to rabbits

The pharmacokinetics of danofloxacin was studied following intravenous (i.v.), intramuscular (i.m.) and subcutaneous (s.c.) administration of 6 mg/kg to healthy rabbits. Danofloxacin concentration were determined by high-performance liquid chromatography assay with fluorescence detection. Minimal inhibitory concentrations (MICs) assay of danofloxacin against 30 strains of Staphylococcus aureus from several European countries was performed in order to compute pharmacodynamic surrogate markers. The danofloxacin plasma concentration versus time data after i.v. administration could best be described by a two-compartment open model. The disposition of i.m. and subcutaneously administered danofloxacin was best described by a one-compartment model. The terminal half-life for i.v., i.m. and s.c. routes was 4.88, 6.70 and 8.20 h, respectively. Clearance value after i.v. dosing was 0.76 L/kg.h. After i.m. administration, the absolute bioavailability was mean (+/-SD) 102.34 +/- 5.17% and the Cmax was 1.87 mg/L. After s.c. administration, the absolute bioavailability was mean (+/-SD) 96.44 +/- 5.95% and the Cmax was 1.79 mg/L. Danofloxacin shows a favourable pharmacokinetics profile in rabbits reflected by parameters such as a long half-life and a high bioavailability. However, in consideration of the low AUC/MIC indices obtained, its use by i.m. and s.c. route against the S. aureus strains assayed in this study cannot be recommended given the risk for selection of first mutant subpopulations.