The effect of cefotaxime on kinetics of apramycin in E. coli infected broilers. The concentration of apramycin in serum was measured with (HPLC) high performance liquid chromatography. Apramycin's pharmacokinetics was described via a two-compartment open model. Serum concentration and kinetic of apramycin after 10 mg/kg b.wt. single IV injection and IV injection of 10 mg/kg b.wt. of apramycin concurrent with IV injection of 10 mg/kg b.wt. of cefotaxime with a single dose, showed that apramycin was detected in serum till 24 hrs with mean rate 0.200± 0.015 µg/ml and till 12 hrs 0.040± 0.009 µg/ml of infected chickens, with (t_0.5α) of 0.18 ± 0.01 h and 0.14± 0.01h, (t_0.5β) of 4.27± 0.29 h and 1.46± 0.07h, (CL_tot) was 0.10± 0.01L/kg/h and 0.67± 0.04L/kg/h, {V_dss} was 1.11± 0.05L/kg and 1.08± 0.02L/kg in infected chickens respectively. Serum concentration and kinetic of single oral intake of 25 mg/kg b.wt. of apramycin and a single oral intake of 25 mg/kg b.wt. of apramycin concurrent with single IM injection of 10 mg/kg b.wt. of cefotaxime, indicated that apramycin was detected till 8 hrs with mean rate 0.633±0.021 µg/ml and 0.550±0.016 µg/ml in serum of infected chickens, respectively, with C_max 3.273± 0.10 μg/ml and 2.277 ± 0.025 μg/ml at T_max (2.29± 0.06 h and 2.456± 0.005 h, (t_0.5α) was 0.81± 0.14h and 1.421± 0.009 h, {t_{0.5 (β)}} was 1.65± 0.11h and1.414± 0.009 h, AUC 15.25± 0.63 µg/h/ml and 12.661± 0.200 µg/h/ml, bioavailability% was 12.04±0.4%, 33.31±0.32% in infected chickens respectively.