The aim of this study was to develop convulsion by giving pentylenetetrazol and to observe the interaction of this drug with diphenhydramine and phenobarbital in chickens with an evaluation of the interaction of these drugs and their effect on the biochemical parameters. The chicks were divided into five groups, each group containing six birds, control group injected with normal saline at 2ml/kg, second group injected with PTZ at56.5 mg/kg I.P., third group injected with diphenhydramine at dose 2.5 mg/kg I.M., before 20 minutes from injected of PTZ at dose 56.5 mg/kg I.P., forth group injected with phenobarbital at dose 10 mg /kg I.M., before 20 minutes from injected of PTZ at dose 56.5 mg/kg I.P., fifth group injected with diphenhydramineat dose 2.5 mg/kgI.M. and phenobarbital at dose 10 mg /kg I.M. before 20 minutes from injection of PTZ at dose 56.5 mg/kgI.P. The results showed that group which was treated with PTZ alone showed a significant decrease in glutathione concentration in plasma and brain compare with the control group. All groups except the group treated with PTZ diphenhydramine and phenobarbital showed a significantly increased in malondialdehyde concentration in plasma and brain compare with control group, as well as, all groups except the group treated with PTZ and phenobarbital appeared significantly increased in glucose concentration in plasma compared with the control group. In conclusion, the study appeared oxidative stress result in the lipid peroxidation which main reasons for decreasing of glutathione concentration and increasing of malondialdehyde concentration in chicks.