Pharmacokinetic disposition of subcutaneously administered enrofloxacin in goats

The pharmacokinetic disposition of enrofloxacin was studied in goats after subcutaneous (s.c.) administration at a single dose of 7.5 mg/kg body weight. Blood samples were drawn from a jugular vein into heparinized tubes at predetermined time intervals after administration of the drug and the plasma was separated by centrifugation. The concentrations of enrofloxacin in the plasma were determined by a microbiological assay using Escherichia coli as the test organism. The plasma concentration-time data were analysed by non-compartmental methods. Enrofloxacin was rapidly absorbed, an appreciable concentration of the drug (0.30+/-0.13 mug/ml) being present in the plasma by 5 min after s.c. administration. The maximum plasma concentration of enrofloxacin and the time to reach that maximum were 2.91+/-0.39 mug/ml and 2.9+/-0.51 h, respectively. A detectable concentration of enrofloxacin persisted in the plasma for 12 h. The elimination half-life and mean residence time of enrofloxacin were 2.84+/-0.57 and 5.74+/-0.28 h, respectively. It is suggested that enrofloxacin given subcutaneously may be useful in the treatment of susceptible bacterial infections in goats.