Comparison of hypersensitivity reactions of intravenous iron: iron isomaltoside-1000 (Monofer®) versus ferric carboxy-maltose (Ferinject®). A single center, cohort study

Aims Intravenous iron supplementation is widely used to treat iron deficiency and iron deficiency anemia when oral iron administration is ineffective or poorly tolerated. Hypersensitivity reactions (HSRs) during infusions are rare, but can be life-threatening. This study aimed to compare the risk for HSRs with the intravenous administration of iron isomaltoside-1000 and ferric carboxymaltose for the treatment of iron deficiency and iron deficiency anemia. Methods This was a single-centre cohort study. Nurses and physicians were instructed to fill out an HSR registration form with every administration of intravenous iron. HSRs were distinguished into serious and non-serious HSRs using the Ring and Messmer classification. Results HSRs occurred in 18/836 (2.1%) ferric carboxymaltose and 43/496 (8.7%) iron isomaltoside-1000 administrations. The crude risk for HSRs was 75% lower after ferric carboxymaltose treatment (RR = 0.248, 95% CI: 0.145-0.426, P < 0.0001). The risk for grade II HSRs was 88% lower after ferric carboxymaltoside (RR = 0.123, 95% CI: 0.051-0.294). The likelihood of HSRs was 3.4 times higher after the administration of iron isomaltoside-1000 (95% CI: 1.910-6.093, P < 0.0001). Regardless of the type of intravenous iron, patients with comorbidities have a factor 3.6 higher risk (95% CI: 1.899-6.739, P < 0.0001). Conclusions Ferric carboxymaltose is associated with a 75% lower risk for HSRs compared with iron isomaltoside-1000 in our population. The presence of a comorbidity raises the likelihood of an HSR by a factor of three regardless of the type of intravenous iron infusion. Further research is needed to clarify the underlying mechanism in various patient groups.