Pharmacokinetic-pharmacodynamic integration of orbifloxacin in Japanese quail (Coturnix japonica) following oral and intravenous administration

The pharmacokinetics of single-dose administration of orbifloxacin were determined in Japanese quail (Coturnix japonica) at dosages of 5mg/kg intravenous (i.v. n=12) and 7.5mg/kg oral (p.o.; n=5), 10mg/kg p.o. (n=5), 15mg/kg p.o. (n=12) and 20mg/kg p.o. (n=5) via HPLC. Orbifloxacin minimal inhibitory concentrations (MICs) against 22 microbial isolates from various bird species were performed to calculate pharmacodynamic surrogate markers. The concentration-time data were analyzed using a naïve pooled data (NPD) approach and compartmental and noncompartmental methods. Steady-state volume of distribution (Vd _ss) and total body clearance (Cl) after i.v. administration were estimated to be 1.27L/kg and 0.60L/h·kg, respectively. Following 15 and 20mg/kg p.o. dose, bioavailability was 102% and 117%, respectively. The harmonic mean of the corresponding terminal half-lives (T _1/2λ _z) across all the dose groups was 1.71h. The C _max/MIC ₉₀ and AUC _0∞24/MIC ₉₀ for the 15 and 20mg/kg p.o. doses were ≥5.22 and ≥8.98, and ≥25.80 and ≥39.37h, respectively. The results of this study suggest that 20mg/kg orbifloxacin p.o. would be a rational daily dose to treat susceptible infections in Japanese quail not intended for food consumption. For more sensitive bacterial organisms, 15mg/kg p.o. may also be effective.