D. Dimitrova, V. Katsarov, D. Tsoneva

Abstract. Investigation of the pharmacokinetics of pefloxacin and its metabolite norfloxacin after single intramuscular application of pefloxacin mesylate at 10 mg/kg in pigs. The study was performed on eight healthy pigs, about 60 days of age. Blood plasma pefloxacin and norfloxacin concentrations were determined by a validated HPLC assay with UV detection. The primary pharmacokinetic parameters of pefloxacin were calculated by the two-compartmental method, whereas those of norfloxacin – by the non-compartmental method. The pharmacokinetic parameters of pefloxacin (mean±SEM) were as followed: elimination half-life (t ) – 6.68 0.52 h, mean residence time (MRT) – 9.71 0.54 h, maximum plasma concentrations (C ) – 0.594±0.12 μg/ml, time to reach C (T ) – 1/2β max max max 1.14±0.03 h, area under the plasma concentration curve from hour 0 to hour 36 (AUC ) – 6.06±0.18 μg.h/ml. Combined effective plasma concentrations of 0-36 h pefloxacin plus norfloxacin over 0.259 μg/ml were detected until the 12th hour after injection, and levels over 0.06 μg/ml – until the 24th hour. Pefloxacin 5 % solution, applied intramuscularly to pigs at a dose of 10.0 mg/kg resulted in effective plasma antimicrobial concentrations against clinically important bacterial infections for 12–24 h.