Intravenous Ferric Carboxymaltose Versus Oral Ferrous Sulfate for Iron Deficiency Anemia: A Retrospective Cohort Study of Iron Store Repletion and Safety

Abstract

Background Iron-deficiency anemia (IDA) is a major clinical burden, particularly when caused by gastrointestinal or gynecological blood loss and mucosal malabsorption. Oral iron supplementation, while widely accessible, is frequently limited by poor gastrointestinal tolerability and inadequate absorption. Intravenous (IV) iron offers a more direct route to iron repletion, yet real-world comparative data from resource-limited settings remain scarce. Methods We conducted a retrospective observational cohort study of 225 patients with IDA managed at the Hematology Department of Cheikh Khalifa Hospital, Mohammed VI University of Health Sciences (UM6SS), Casablanca, Morocco, between January 2020 and December 2023. Patients received either oral ferrous sulfate (n=185) or IV ferric carboxymaltose (n=40) based on clinical indication. The primary efficacy endpoint was post-treatment serum ferritin at three months, the only post-treatment laboratory parameter systematically available across both groups. Secondary endpoints included transfusion requirement and adverse event profile. Results Both groups were well-matched at baseline across all haematological parameters (hemoglobin (Hb): 8.98±2.23 vs. 8.50±1.42 g/dL, p=0.196; ferritin: 5.57±4.25 vs. 4.71±2.96 µg/L, p=0.221). IV iron was associated with dramatically superior iron store repletion at three months (post-treatment ferritin: 412.60±95.87 vs. 8.68±4.38 µg/L; p<0.001), representing approximately a 47-fold difference. Oral iron recipients remained below the accepted thresholds for adequate store repletion (≥30 µg/L) at follow-up. Transfusion rates were 10.3% (19/185) oral vs. 17.5% (7/40) IV, a non-significant difference (p=0.306), reflecting greater baseline severity in the IV group. Gastrointestinal adverse events occurred in 100% of oral iron recipients, while systemic reactions (predominantly arthralgia, myalgia, and fever) occurred in 50% (20/40) of IV iron recipients; one anaphylactic reaction (1/40; 2.5%) was successfully managed. Conclusion In this real-world cohort, IV ferric carboxymaltose achieved markedly superior iron-store repletion compared to oral ferrous sulfate, with a better gastrointestinal tolerability profile, at the cost of a distinct systemic adverse event profile requiring clinical monitoring. These findings support broader consideration of IV iron in patients with IDA who have failed, or are unlikely to benefit from, oral therapy, particularly those with pre-existing mucosal pathology or ongoing haemorrhagic loss.