Effects of low-dose magnesium oxide on elevated serum magnesium levels and improved constipation in hemodialysis patients: a single-center retrospective study

Abstract

Abstract Background The prevention of hypomagnesemia is critical for improving the life expectancy of patients undergoing hemodialysis (HD). The administration of magnesium oxide (MgO) increases serum Mg concentrations; however, dose adjustments must be done carefully owing to the risk of hypermagnesemia in patients undergoing HD. Additionally, the laxative effects of low-dose MgO on constipation in these patients has not been reported. Therefore, in the present study, we investigated the effects of treatment with low-dose MgO on serum Mg concentration changes and the improvement of defecation in patients undergoing HD. Methods The present study was a single-center retrospective observational study of 43 patients undergoing maintenance HD at Shirasagi Hospital. The patients’ clinical characteristics, including serum Mg concentration, were obtained from the hospital’s electronic medical records. In the group who received MgO for constipation, the effectiveness of MgO as a laxative was categorized as effective, ineffective, or unknown on the basis of electronic medical records related to defecation. Results Of the 43 patients included in the present study, 23 were prescribed supplemental Mg to prevent hypomagnesemia or maintain mild hypermagnesemia and 19 to prevent constipation. All patients received diasylate with an Mg concentration of 1.0 mEq/L. Additionally, 37 patients (86%) were treated with 330 mg/day MgO. The serum Mg concentrations before and 1, 2, and 3 months after the start of MgO were 2.3 ± 0.2, 2.8 ± 0.4, 2.8 ± 0.5, and 2.8 ± 0.4 mg/dL, respectively (P < 0.001). Multiple linear regression analysis showed that dry weight was independently associated with changes in serum Mg concentration from before to 1 month after MgO administration (regression coefficient = −0.027; P = 0.020). Of the 19 patients evaluated for constipation, 8 (42%) had documented effective bowel movements after the initiation of MgO, 6 had no effect, and 5 were unknown; however, 1 patient in the ineffective group and 2 in the effective group used other laxatives prior to starting MgO. Conclusions The results of the present study suggest that the administration of low-dose MgO to patients undergoing HD provides a means of increasing serum Mg concentration without causing dangerous hypermagnesemia, that serum Mg concentrations increase relatively easily in lower-weight patients. In addition, this study shows that low-dose MgO may be effective as an initial treatment for constipation in this patient group in a cautious manner, but this study did not provide sufficient data for the usefulness of low-dose MgO for constipation in patients undergoing HD.