Switching from Cation-Exchange Resin to Sodium Zirconium Cyclosilicate Hydrate in Patients on Hemodialysis

Background/Objectives: Hyperkalemia is a common complication in patients receiving maintenance hemodialysis (HD). Conventional cation-exchange resins, including sodium polystyrene sulfonate (SPS) and calcium polystyrene sulfonate (CPS), effectively lower serum potassium but may non-selectively bind magnesium. Sodium zirconium cyclosilicate (SZC) is a highly selective potassium binder with minimal affinity for magnesium. This study investigated changes in serum cation profiles and nutritional status after switching from conventional cation-exchange resins to SZC in patients undergoing maintenance HD. Methods: In this prospective, single-arm, before-and-after study conducted in routine clinical practice, 28 maintenance HD patients receiving SPS or CPS for chronic hyperkalemia were switched to SZC and followed for 12 weeks. Serum potassium, magnesium, corrected calcium, phosphorus, whole parathyroid hormone (whole-PTH), albumin, and the Geriatric Nutritional Risk Index (GNRI) were evaluated before and after the treatment transition. Results: Following the switch to SZC, median serum potassium increased modestly from 5.01 (4.66-5.39) to 5.26 (4.89-5.48) mEq/L (p = 0.031), whereas serum magnesium increased from 2.46 (2.29-2.66) to 2.66 (2.35-2.93) mg/dL (p < 0.001). Serum calcium, phosphorus, whole-PTH, albumin, and GNRI remained unchanged. Subgroup, correlation, and longitudinal analyses consistently supported the robustness of the observed increase in serum magnesium, irrespective of the previously prescribed resin or concomitant proton pump inhibitor use. Conclusions: Switching from conventional cation-exchange resins to SZC was associated with a significant increase in serum magnesium concentrations while maintaining acceptable potassium control and stable nutritional status in maintenance HD patients. These findings are consistent with the greater cation selectivity of SZC and suggest that replacement of conventional cation-exchange resins may contribute to preservation of serum magnesium concentrations. Further multicenter prospective studies evaluating magnesium metabolism together with clinically relevant outcomes are warranted to confirm these findings and clarify their clinical significance.