BACKGROUND: Carbon monoxide poisoning(COP) is an important cause of mortality and morbidity worldwide. This study was to investigate the levels of serum paraoxonase(PON), arylesterase(ARYL), ceruloplasmin(Cp), and sulfhydryl(-SH) in the treatment of COP, and to further understand the pathophysiology of COP.METHODS: This prospective study comprised 107 individuals with COP(group 1) and 50 healthy volunteers(group 2). Serum, plasma, and erythrocyte samples were taken on admission from all participants with COP. This process was repeated in the 90 th and 180 th minutes of treatment. Samples were taken from the control group only once. The levels of plasma PON, ARYL, Cp activity and-SH were measured in both groups.RESULTS: Age, gender, and carboxyhemoglobin level were not correlated with PON, ARYL, Cp, and-SH levels. PON, ARYL, and-SH levels were signifi cantly decreased in group 1 compared with group 2. Conversely, Cp was signifi cantly elevated in group 1 in contrast to group 2. Although ARYL was lower on admission in patients with COP than that was observed in the 90 th and 180 th minutes(P<0.001), Cp was higher on admission than at the other time points(P<0.001).CONCLUSIONS: Participants with COP had decreased levels of antioxidants(PON, ARLY, and-SH). COP represses the antioxidant system. BACKGROUND: Carbon monoxide poisoning (COP) is an important cause of mortality and morbidity worldwide. This study was to investigate the levels of serum paraoxonase (PON), arylesterase (ARYL), ceruloplasmin (Cp), and sulfhydryl (-SH) in the treatment of COP, and to further understand the pathophysiology of COP.METHODS: This prospective study was 107 individuals with COP (group 1) and 50 healthy volunteers (group 2). Serum, plasma, and erythrocyte samples were taken on admission from all participants with COP. This process was repeated in the 90th and 180 th minutes of treatment. Samples were taken from the control group only once. The levels of plasma PON, ARYL, Cp activity and-SH were measured in both groups .RESULTS: Age , gender, and carboxyhemoglobin levels were not correlated with PON, ARYL, Cp, and-SH levels. PON, ARYL, and-SH levels were signifi cantly decreased in group 1 compared with group 2. Conversely, Cp was signifi cantly elevated in group 1 in contrast to group 2. Although ARYL was lower on admission in patients with COP than that was observed in the 90th and 180 th minutes (P <0.001), Cp was higher on admission than at the other time points (P <0.001) .CONCLUSIONS: Participants with COP had decreased levels of antioxidants (PON, ARLY, and-SH). COP represses the antioxidant system.