Pharmacokinetics, tissue residue and plasma protein binding of ofloxacin in goats

Ofloxacin was administered to six male goats intravenously (5 mg/kg) to determine its kinetic behavior, tissue residue, in vitro plasma protein binding and to compute a rational dosage regimen. The concentration of ofloxacin in plasma and tissue samples collected at prescheduled time were estimated by using HPLC. The pharmacokinetic parameters were determined by non-compartmental model and plasma protein binding was estimated by equilibrium dialysis technique. The therapeutic concentration (> or =0.5 microg/ml) was maintained up to 36 h and the initial concentration at 2.5 min (14.76 +/- 0.47 microg/ml) declined to 0.05 +/- 0.03 microg/ml at 96 h with a secondary peak (0.64 +/- 0.15 microg/ml) at 24 h. The mean AUC, AUMC, t1/2, MRT, Cl and Vd were calculated to be 58.94 +/- 19.43 microg x h/ml, 1539.57 +/- 724.69 microg x h2/ml, 15.58 +/- 1.87 h, 22.46 +/- 2.71 h, 135.60 +/- 31.12 ml/h/kg and 2.85 +/- 0.74 L/kg respectively. Significantly high concentration of drug was detected in different tissues after 24 h of intravenous dosing of 5 mg/kg, at 24 h interval for 5 days. The in vitro plasma protein binding of ofloxacin was found to be 15.28 +/- 0.94%. Based on these kinetic parameters, a loading dose of 5 mg/kg followed by the maintenance dose of 3 mg/kg at 24 h dosing interval by intravenous route is recommended.