Intravenous iron tied to low anaphylaxis risk

The rates of anaphylaxis among commonly used intravenous (IV) iron formulations are low, but those for iron dextran and ferumoxytol are three- to eightfold higher compared to iron sucrose, results of a recent study have shown.

A group of researchers compared the risks for anaphylaxis among five IV iron products in this retrospective cohort study using a target trial emulation framework. They obtained Medicare fee-for-service data with Part D coverage between July 2013 and December 2018 from older adults receiving their first IV iron administration.

The occurrence of anaphylaxis within 1 day of IV iron administration, verified through a validated case definition, was the primary outcome. The researchers adjusted the analysis for 40 baseline covariates using inverse probability of treatment weighting and computed the adjusted incidence rates (IRs) for anaphylaxis per 10,000 first administrations and odds ratios (ORs).

Adjusted IRs were 9.8 cases (95 percent confidence interval [CI], 6.2‒15.3) for iron dextran, 4.0 cases (95 percent CI, 2.5‒6.6) for ferumoxytol, 1.5 cases (95 percent CI, 0.3‒6.6) for ferric gluconate, 1.2 cases (95 percent CI, 0.6‒2.5) for iron sucrose, and 0.8 cases (95 percent CI, 0.3‒2.6) for ferric carboxymaltose.

The adjusted ORs for anaphylaxis, using iron sucrose as reference, were 8.3 (95 percent CI, 3.5‒19.7) and 3.4 (95 percent CI, 1.4‒8.3) for iron dextran and ferumoxytol, respectively.

Notably, no significant change occurred in the risk for anaphylaxis associated with low-molecular-weight iron dextran (OR, 8.4, 95 percent CI, 2.8‒24.7) when cohort entry was restricted to the period after withdrawal of high-molecular-weight iron dextran from the US market in 2014, the researchers said.

Additionally, only patients in the iron dextran or ferumoxytol group had an incidence of anaphylactic reactions that required hospital admission.