Evaluation of the short and long-term effects of ferric carboxymaltose on phosphorus and parathyroid hormone levels in patients with CKD

Context: Ferric carboxymaltose (FCM) is a widely used therapy in chronic kidney disease (CKD). With its increasing use, hypophosphatemia -an unexpected side effect- has drawn growing attention. While the risk of hypophosphatemia decreases as the chronic kidney disease stage progresses, the impact of ferric carboxymaltose on parathormone levels and how this risk evolves with repeated doses remain less known. Objective: In our study, we planned to evaluate the relationship of ferric carboxymaltose with phosphorus and parathormone in the long term in patients with stage 2-5 non-dialysis chronic kidney disease. Method: All chronic kidney disease patients who received ferric carboxymaltose treatment between January 2022 and March 2023 were screened. Basal phosphorus values of the patients and phosphorus values in the first and second controls were recorded as F0, F1, and F2, respectively. Parathormone values were recorded in the first control after the second dose of ferric carboxymaltose. Results: A total of 49 patients met the criteria, of whom 31 patients were female (63%). Thirty-two patients (65%) received a single dose of treatment. The mean age was 67±12, with a mean dose of 969±483 mg. The mean GFR was 36±14. When comparing single- and double-dose groups, no significant differences were observed in age, gender distribution, chronic kidney disease stage, baseline phosphorus levels (F0), or the time to the first follow-up. Between F0 and F1, there was a significant decrease of 0.2 and 0.3 mg/dL in phosphorus levels in both groups, respectively. No patient developed clinically apparent hypophosphatemia. No significant difference was found when the F0-F2 and F1-F2 values were compared in patients who received two treatment doses. Parathormone levels increased slightly in the same patient group, although not statistically significant. Conclusion: While ferric carboxymaltose causes a mild phosphorus reduction at high doses in chronic kidney disease patients not receiving dialysis treatment, this effect is not permanent. Prospective studies with sufficient patients are needed to elucidate the impact of fluctuations in phosphorus levels caused by this treatment on parathormone and chronic kidney disease -related bone disease.