Pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin in healthy buffalo calves

In the present study, pharmacokinetics and testing of dosage regimen was carried out in four healthy female buffalo calves after its i.v. administration @ 4 mg.kg^-1. Estimation of enrofloxacin and its active metabolite ciprofloxacin were done by using High Performance Liquid Chromatography (HPLC). The study revealed that enrofloxacin followed 2-compartment open model while ciprofloxacin followed non-compartment model. Mean ± S.E.M. distribution half life (t1/2 β), elimination half life (t1/2 β), mean residential time (MRT), volume distribution at steady state (VdSS) and total body clearance (ClB) of 0.28 ± 0.05 h, 2.95 ± 0.52 h, 2.91 ± 1.90 h, 5.38 ± 1.34 L.kg^-1 and 34.58 ± 6.79 ml.kg^-1.min^-1 were obtained for enrofloxacin while t1/2 β, MRT, VdSS and ClB of 2.79 ± 0.28 h, 3.60 ± 0.58 h, 13.19 ± 1.49 L.kg^-1 and 68.85 ± 16.03 ml.kg^-1. min^-1 were noted for ciprofloxacin. A % conversion of 51.86 ± 16.03 of enrofloxacin to ciprofloxacin occurred. Combined minimum therapeutic concentration of enrofloxacin + ciprofloxacin (Cp "min = minimum therapeutic concentration) of d” 0.25 μg.ml^-1 was maintained from 0.048 - 6 h. Calculated dosage of enrofloxacin + ciprofloxacin for repetitive administration revealed a loading dose (D*) of 5.05 ± 0.65 mg.kg^-1 and maintenance dose (D0) of 4.06 mg.kg^-1 was calculated in the present study.