We would like to thank Dr. Ozsoylu for his comments on our article “Safety profiles of Fe2+ and Fe3+ oral preparations in the treatment of iron deficiency anemia in children” Citation[1]. Although the final conclusion that ferrous sulfate is more efficient and better tolerated than ferri polymaltose complexes is shared by both our group and Dr. Ozsoylu, his letter brings forth some questions and comments, which are answered here.
As Dr. Ozsoylu pointed out, a few patients had Hb levels lower than 11 g/dL at the third and sixth months in the ferric iron group. However, these variations did not lead to any change in mean levels, statistical analysis, and main outcome of this study. Moreover, our publication was not an efficacy study; it was a safety study.
Dr. Ozsoylu contributes that catalase enzyme activity is lower in iron-deficiency anemia and that this has been reported in his previous work, proposing that our data do not fit this result. Since our work was originally planned mainly as a self-control, prospective study, we did not include any remarks on the catalase activity of our study group compared with healthy controls. Dr. Ozsoylu also raises questions on the appropriateness of our catalase unit (U/Hb). Although catalase activity is a function of the cell, according to the International Union of Biochemistry (IUB) recommendations, it is not possible to define international catalase units due to abnormal kinetics of the enzyme. The use of various defined units is therefore acceptable for this enzyme. Use of the rate constant of a first-order reaction is the most recommended. It is proposed that the rate constant related to the hemoglobin content can serve as a measure of the specific activity of erythrocyte catalase [Citation[2], Citation[3]]. This is supported by a large number of reports in which catalase activity is given as U/Hb and here we present two very recent reports as supporting examples [Citation[4], Citation[5]].
On the other hand, the main focus of study was to investigate the safety of oral iron preparations. Apart from catalase and SOD activities as known markers, we also determined the LDL oxidations and copper-stimulated LDL oxidations in LDL samples and 8-isoprostane levels in urine to be current markers of oxidative stress. There were minimal differences among children treated with ferric and ferrous iron preparations in respect of clinical toxities and laboratory analysis Citation[1].
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