Effects of ferric carboxymaltose on hypophosphatemia in patients with iron deficiency anemia: A single-center retrospective study

A retrospective analysis was conducted to assess hypophosphatemia and associated hormonal alterations in patients with iron deficiency anemia treated with ferric carboxymaltose (FCM). Overall, 163 patients were evaluated. Hematological and biochemical parameters, including phosphorus, calcium, magnesium, parathyroid hormone (PTH), and 1,25-dihydroxy vitamin D, were evaluated before and after FCM administration. For the purposes of this study, serum phosphorus levels below 2.5 mg/dL were considered indicative of hypophosphatemia, whereas levels below 1 mg/dL were classified as severe hypophosphatemia. Of the patients, 20.9% were male (n = 34) and 79.1% were female (n = 129). The median age was 56 years (25th–75th percentile: 45–71). Fifty-four patients (33%) received 500 mg and 109 patients (67%) received 1000 mg of FCM. Serum phosphorus levels measured on day 14 after treatment were significantly lower compared to baseline values (3.4 ± 0.6 vs. 2.4 ± 0.9; p < 0.001). Hypophosphatemia developed in 91 patients (55.8%). While serum phosphorus levels decreased significantly, PTH levels increased (72.7 [50.7–105.3] vs. 84.4 [60.7–122.6]; p < 0.001), and 1,25-dihydroxy vitamin D levels showed a significant decline (35.8 ± 15.5 to 26.7 ± 16.2). A significantly higher risk of hypophosphatemia was observed among patients receiving 1000 mg FCM compared with those receiving 500 mg (3.7-fold increase, p = 0.001). Moreover, the rate of hypophosphatemia detected in our study population was comparable to previously published data. Although FCM provides rapid improvement in hematological parameters, it is associated with transient, dose-dependent hypophosphatemia. Hypophosphatemia occurred in 55.8% of patients and was significantly more frequent in patients receiving 1000 mg ferric carboxymaltose.