A recent Rutgers study found that two common intravenous (IV) iron products used to treat iron deficiency are more likely to cause anaphylactic reactions than the others.
Chintan Dave, lead author of the study and an assistant professor at Ernest Mario School of Pharmacy, said IV iron products are typically recommended for iron-deficient patients who have difficulty orally ingesting iron pills.
He said the origin of the study came from a noticeable lack of research on the risks of allergic reactions to IV iron products.
Dave said the study’s researchers analyzed 167,000 Medicare records of elderly patients who were administered IV iron medication to find patterns in allergic reactions.
He said they looked specifically at patients who used any one of the five most common kinds of iron IV — iron dextran, ferumoxytol, ferric carboxymaltose, ferric gluconate and iron sucrose — and compared the rate of allergic reaction to the type of IV iron medication.
“For the study, the researchers used advanced statistical methods and pharmacoepidemiologic techniques, which are tailor-made for studying the safety and effectiveness of medications using large observational databases,” Dave said.
Iron dextran had the highest incidence of severe allergic reaction with a rate of approximately 10 cases of anaphylaxis per 10,000 iron IV infusions, according to the study. This was followed by ferumoxytol, which had an anaphylaxis incidence rate of four cases per 10,000.
Dave said that these incidence rates are still very low by themselves, but the findings are significant if compared to the different medications’ incidence rates.
Comparatively, the study found that the anaphylaxis incidence rates for ferric carboxymaltose, ferric gluconate and iron sucrose ranged from 0.8 to 1.5 cases of anaphylaxis per 10,000 iron IV infusions.
“We conclude by saying that the rates of anaphylaxis were very low with all IV iron products, but three- to eight-fold greater for iron dextran and ferumoxytol compared with iron sucrose,” Dave said.
While the exact reason why some IV iron products can cause anaphylaxis is yet to be confirmed, it could be related to the composition of the different formulations themselves, according to the study.
All IV iron formulations are made up of a carbohydrate shell covering an iron core, but the characteristics of the shell can change depending on the product. Products containing substances like dextran may have greater capacity for causing anaphylaxis, according to the study.
Dave said that this study’s findings correspond with prior data pointing to some IV iron medications increasing the likelihood of anaphylaxis. Though deciding what IV iron product a patient should use involves evaluating other factors in addition to anaphylaxis risk, he said.
“These (deciding) factors include not only the risk of anaphylaxis but also other factors such as the clinical indication, number of IV iron administrations required, risk of other adverse reactions and cost,” Dave said.
The study also acknowledged its own limitations, stating that it has only assessed the risk of anaphylaxis based on older adults using Medicare, and its conclusions may not directly apply to younger IV iron users, who are generally at less risk of anaphylaxis.
“Our investigation offers an important step in understanding the differences in the risk for anaphylaxis due to IV iron use,” the study said. “By clarifying the risk for this rare but severe adverse reaction, this information can contribute to the choice of IV iron preparations.”