Levofloxacin pharmacokinetics and tissue residue concentrations after oral administration in Bilgorajska geese

1. The aim of this study was to assess the pharmacokinetics of levofloxacin, a third-generation fluoro-quinolone antimicrobial drug, in geese (n = 26) after either single intravenous or oral administration, and to evaluate the depletion profile in goose muscle, heart, liver, kidney and lung after a single oral dose. 

2. The pharmacokinetic study involved 16 geese which were randomly divided into two groups (n = 8/group), the first received levofloxacin (2 mg/kg) intravenously while the second was treated with orally (5 mg/kg). The tissue depletion study involved 10 geese which were dosed orally (5 mg/kg) and two animals were killed at different time-points in order to collect the selected tissues. Levofloxacin was quantified in all the matrices tested by a validated high-performance liquid chromatography (HPLC) method, using a spectrofluorimetric detector. The pharmacokinetics were analysed using a non-compartmental model. 

3. Plasma concentrations were quantified after up to 24 h in animals administered intravenously and up to 48 h after oral treatment. Levofloxacin was rapidly absorbed after oral administration (Tmax = 0.38 h) showing high bioavailability (95.57 ± 20.61%). The drug showed a moderate volume of distribution (1.40 ± 0.28 ml/g) and rapid clearance (0.28 ± 0.06 ml/g/h). No statistical differences in estimates were found between the two different administration methods (P > 0.05). Drug residues were highest at 6 h and decreased constantly up to 48 h in all the selected tissues. Liver and kidney had the highest levofloxacin concentrations. 

4. According to the pharmacokinetic/pharmacodynamic surrogate index (AUC/MIC) the levofloxacin dose regimen (after oral administration) used in the present study could be active against bacteria at a minimum inhibitory concentration (MIC) > 0.24 μg/ml in geese. In addition, drug accumulation in the liver might be controlled using an estimated preliminary withdrawal time of 90 h.