[Pharmacokinetics of baytril (enrofloxacin) in dogs]

Baytril with the active ingredient enrofloxacin was given to four dogs in a single intravenous and oral dose of 5 mg/kg body weight. Measured plasma concentrations were different depending on the method of analysis used. Using high performance liquid chromatography quantitative determination of both enrofloxacin and its main metabolite ciprofloxacin is possible whereas antimicrobially active substance is measured by bioassay. Ciprofloxacin occurred early in the concentration-time curves after intravenous and oral administration of the parent drug enrofloxacin with cmax 0.2 and 0.3 microgram/ml, respectively, at tmax 2 and 4 h, respectively. Areas under the curve (AUC) calculated from concentration-time-curves with bioassay data are overestimated, because ciprofloxacin may be more active than enrofloxacin against E. coli 14 (ICB 4004) used in this test. Thus, pharmacokinetic parameters which are derived from AUC-values are overestimated, too. Oral bioavailability calculated with bioassay results was more than 100% whereas availability of enrofloxacin was only 53%. Clearance was 10.3 ml/min.kg (antimicrobially active substance) and 27.1 ml/min.kg (enrofloxacin). Elimination half life was 3.7 and 2.4 h, respectively.