The Effectiveness and Safety of Calcium Carbonate Use in Chronic Kidney Disease Patients with Normophosphatemia

Background: Patients with early and moderate stages of chronic kidney disease (CKD) have normal serum phosphate levels. Increased fibroblast growth factor-23 (FGF23) levels in these patients are responsible for maintaining normophosphatemia status by increasing the excretion of phosphate through urine. However, an increased serum FGF23 level is related to cardiomegaly, vascular calcification, CKD progression, and mortality. This study aimed to examine the effectiveness and safety of calcium carbonate use in stage 3 or 4 CKD patients with normophosphatemia. Methods: This double-blind randomized controlled trial (ClinicalTrials.gov identifier NCT03550534) included stage 3 or 4 CKD patients with normophosphatemia who visited the nephrology or endocrinology clinic at Dr. Cipto Mangunkusumo Hospital. Forty-six subjects were randomized to receive either calcium carbonate or placebo over a 12-weeks period. Urine phosphate, serum phosphate, serum calcium, and serum intact FGF23 levels were measured before and after the intervention. Results: The baseline characteristics of the two groups were similar, except for the higher prevalence of dyslipidemia in the placebo group. The CaCO₃ group had shown reduced levels of FGF23 compared to the placebo group,-8.03 vs. 0.15 pg/ml respectively (p = 0.019). The median level of FGF23 showed a significant decrease only in the CaCO₃ group. An increase in eGFR and a slightly decrease in urine phosphate were observed in the CaCO₃ group; however, the data was found to be statistically not significant. No significant changes were noted in the serum calcium levels in both groups. Conclusion: The administration of calcium carbonate has been shown to be effective and safe for moderate CKD patients with normophosphatemia due to its effect in lowering FGF23 levels without escalating the serum calcium level.