Pharmacokinetics, urinary excretion and plasma protein binding of danofloxacin following intravenous administration in buffalo calves (Bubalus bubalis)

Pharmacokinetics, urinary excretion and plasma protein binding of danofloxacin was investigated in buffalo calves following intravenous administration at the dose rate of 1.25 mg/kg to select the optimal dosage regimen of danofloxacin. Drug concentrations in plasma and urine were measured by microbiological assaying. In vitro plasma protein binding was determined employing the equilibrium dialysis technique. The distribution and elimination of danofloxacin were rapid, as indicated by values (mean +/- SD) of distribution half-life (t(1/2)alpha = 0.16 +/- 0.07 h) and elimination half-life (t(1/2)beta = 4.24 +/- 1.78 h), respectively. Volume of distribution at steady state (Vss) = 3.98 +/- 1.69 L/kg indicated large distribution of drug. The area under plasma drug concentration versus time curve (AUC) was 1.79 +/- 0.28 mu g/mlxh and MRT was 8.64 +/- 0.61 h. Urinary excretion of danofloxacin was 23% within 48 h of its administration. Mean plasma protein binding was 36% at concentrations ranging from 0.0125 mu g/ml to 1 mu g/ml. On the basis of pharmacokinetic parameters obtained, it is concluded that the revision of danofloxacin dosage regimen in buffalo calves is needed because the current dosage schedule (1.25 mg/kg) is likely to promote resistance.