Disposition kinetics of enrofloxacin and ciprofloxacin following intravenous administration of enrofloxacin in goats

Pharmacokinetic properties of the antimicrobial fluoroquinolone, enrofloxacin, were studied in female goats. Enrofloxacin was given to goats in a single dose of 2.5 mg kg-E body weight by intravenous (i.v.) route. Blood samples were collected via jugular venipuncture into heparinized tubes at predetermined times after drug administration. Plasma concentrations of enrofloxacin and its active metabolite ciprofloxacin were simultaneously determined by reversed-phase high performance liquid chromatography. The decline of enrofloxacin concentrations in plasma after the drug administration was best described by a biexponential equation. A rapid distribution phase was followed by the slower elimination phase with a half-life (t(1/2beta)) Of 0.73 +/- 0.047 h. The volume of distribution (V-d(area)), total systemic clearance (Cl-B), and mean residence time (MRT) of enrofloxacin were 1.38 +/- 0.0451 kg(-1), 1331 +/- 93.64 ml h(-1) kg(-1) and 0.97 +/- 0.051 h, respectively. The ratio between the area under the plasma concentration-time curves (AUCs) of ciprofloxacin and enrofloxacin was 0.24. The AUC, t(1/2beta) and MRT of ciprofloxacin were 0.44 +/- 0.02 mug h ml(-1), 0.92 +/- 0.13 and 1.93 +/- 0.19 h, respectively. The combined enrofloxacin and ciprofloxacin concentrations in plasma (greater than or equal to0.1 mug ml(-1)) were maintained up to 3 h after enrofloxacin administration. It appears that enrofloxacin can be useful for the treatment of goat diseases associated with pathogens that are sensitive to the drug. (C) 2002 Elsevier Science B.V. All rights reserved.