Some pharmacokinetic parameters of pefloxacin in lactating goats

The aim of this study was to elucidate some of the pharmacokinetic parameters of pefloxacin in lactating goats (eta = 5) following intravenous (i.v.) or intramuscular (i.m.) injections of 10 mg/kg bw. Serially obtained serum, milk and urine samples were collected at precise time intervals, and the drug concentrations were assayed using a microbiological assay. A two-compartment open model best described the decrease of pefloxacin concentration in the serum after intravenous administration. The maximum serum concentration (C-p(0)) was 8.4+/-0.48 mug/ml; elimination half-life (t(1)/2beta) was 1.6+/-0.3 h; total body clearance (Cl(t)ot) was 3.6+/-0.3 L/kg/h; steady-state volume of distribution (V(d)ss) was 5.14+/-0.21 L/kg; and the area under the curve (AUC) was 2.78+/-0.22 mug.ml/h. Pefloxacin was absorbed rapidly after i.m. injection with an absorption half-life (t(1)/2ab) of 0.32+/-0.02 h. The peak serum concentration (C(m)ax) of 0.86+/-0.08 mug/ml was attained at 0.75 h (T(m)ax). The absolute bioavailability after i.m. administration was 70.63+/-1.13% and the serum protein-bound fraction ranged from 7.2% to 14.3%, with an average value of 9.8+/-1.6%. Penetration of pefloxacin from the blood into the milk was rapid and extensive, and the pefloxacin concentration in milk exceeded that in serum from 1 h after administration. The drug was detected in milk and urine for 10 and 72 h, respectively; no samples were taken after 72 h.