Pharmacokinetics of ceftazidime in buffalo calves following intravenous and intramuscular administration

The pharmacokinetic parameters of ceftazidime, a third generation cephalosporin, were investigated in six buffalo calves after single intravenous (IV) and intramuscular (IM) administration at a dose rate of 10 mg/kg body weight. Ceftazidime concentrations in plasma and urine were determined by microbiological assay. Ceftazidime disposition was best fitted by a two-compartmental and a one-compartmental open model with first-order elimination after IV and IM dosing, respectively. After IV administration, distribution was rapid (t1/2α = 0.15 ± 0.01 h) with an area under the ceftazidime plasma concentration/time curve (AUC0-∞) of 253.9 ± 7.8 μg/ml.h and a steady state volume of distribution (Vd(ss)) of 0.18 ± 0.01 L.kg-1. The elimination half life (t½β) and total body clearance were 3.4 ± 0.2 h and 39.5 ± 1.2 ml/kg/h, respectively. Following intramuscular administration, the absorption half life (t1/2ka), peak plasma concentration (Cmax), time to peak plasma concentration (Tmax), AUC0-∞ and bioavailability were 0.25 ± 0.04 h, 45.8 ± 2.7 μg/ml, 0.75 h, 207.9 ± 9.9 μg/ml.h and 81.7 ± 5.9%, respectively. Urinary excretion of ceftazidime was less than 55% 36 h post administration. In vitro plasma protein binding of ceftazidime was 13.1 ± 1.1%. To maintain minimum therapeutic concentration of 4 μg/ml, a satisfactory dosage regimen of ceftazidime in buffalo calves would be 9.4 mg/kg to be repeated at 12 h intervals. In conclusion, ceftazidime (10 mg/kg, IM) shows favorable pharmacokinetic behavior in buffalo calves.