Abstract: AIM: To establish a HPLC method for the determination of levofloxacin in dog plasma and its pharmacokinetics in dogs. METHODS: The plasma protein was precipitated by the addition of 10 % perchloric acid.The resulting supernatant liquid was directly injected after centrifuge and dilution.The chromatography conditions were:DIKMA column (Diamonsil^TM C₁₈ 5 μm, 150 mm ×4.6 mm), methanol-PBS-triethylamine-isopropanol (33 ∶67 ∶0, 14 ∶0.4, adjusted pH to 3.0 with H₃PO₄) as mobile phase with a flow rate of 1.2 ml·min^-1.It was detected by fluorescence detector, and the detection wavelength was λ_ex=295 nm and λ_em=440 nm.Ciprofloxacin was the internal standard. RESULTS: The linear range of calibration curve was within drug plasma concentrations of 0.25-50 mg·L^-1 (r=0.9998), the detection limit was 0.02 mg·L^-1 (S N > 3), the extraction recovery was 83.0 %-85.6 % (n=5), the method recovery was 92.10 %-106.77 %(n=5), the within-day RSD and between-day RSD were 1.3 %-4.0 % and 1.8 %-8.2 % (n=5), respectively. CONCLUSION: The method possesses merits of simplicity, sensitivity, good accuracy, high precision, and fine reproducibility, which is suitable for pharmacokinetic and bioavailability studies of levofloxacin in dogs.

Key words: levofloxacin, HPLC, drug concentration, pharmacokinetics