Ciprofloxacin pharmacokinetics in dogs following oral administration

This paper reports the variation of the pharmacokinetic parameters of ciprofloxacin (CIP) following oral administration of three single doses (10, 20 and 40 mg/kg body weight (b.w.)) to dogs. Plasma and urine samples were assayed by HPLC. The plasma vs. time data were submitted to classical compartmental kinetic analysis (one-compartment open model with a lag time) and to non-compartmental data analysis. The maximal plasma concentrations attained after administration of 10 and 20 mg/kg were 1.55 and 3.08 mg/l, respectively, and agree with results reported in the literature for this species. The absorption was slower and showed a longer and more variable lag time when the dose increased. The elimination rate was significantly smaller after administration of the 40 mg/kg (0.0014/min) than 10 and 20 mg/kg doses (near 0.0024/min). AUC/D also showed significant differences. The non-linearity of CIP pharmacokinetics after oral administration was demonstrated by fitting the data AUC vs. dose to a quadratic equation.