Pharmacokinetics of cefepime in healthy cross-bred calves following single intravenous administration

The disposition kinetics of cefepime after a single intravenous administration at dosage level of 10 mg.kg⁻¹ b.wt. was investigated in healthy cross-bred calves and an appropriate dosage regimen was calculated. Blood samples were collected at different time intervals and the concentration of drug in plasma was estimated by microbiological assay technique. Pharmacokinetic data after intravenous administration was best described by two-compartment open model. The highest plasma concentration of cefepime at 1 min. was 47.8 ± 1.19 μg.ml⁻¹, which declined rapidly to 12.0 ± 0.29 μg.ml⁻¹ at 1 h and after that cefepime gradually disappeared from plasma and a concentration of 0.25 ± 0.02 μg.ml⁻¹ was detected at 24 h. The mean values of distribution rate constant (α) and distribution half-life (t_1/2α) were 5.37 ± 0.71 h⁻¹, 0.14 ± 0.02 h, respectively. The mean values of area under curve (AUC), apparent volume of distribution (Vd_area), mean residence time (MRT) and total duration of pharmacological effect (td) were 72.0 ± 0.40 μg.ml⁻¹.h, 0.61 ± 0.01 L.kg⁻¹, 3.90 ± 0.06 h and 10.0 ± 0.11 h, respectively. The mean values of elimination half-life (t_1/2α) and total body clearance were 3.01 ± 0.03 h and 0.139 ± 0.001 L.kg⁻¹.h⁻¹, respectively. To maintain a minimum therapeutic concentration of cefepime as 1.00 μg.ml⁻¹, a satisfactory dosage regimen of cefepime should be 9.57 mg.kg⁻¹ followed by 8.97 mg.kg⁻¹ repeated at 12 h intervals.