How do I calculate the iron dose and choose the type of iron preparation for a patient requiring intravenous (IV) iron infusions?

From the Guidelines

To calculate the IV iron dose and choose the appropriate preparation, first determine the patient's iron deficit using the Ganzoni formula: Total iron deficit (mg) = Body weight (kg) × (Target Hb - Actual Hb) (g/dL) × 2.4 + Iron stores (mg), and consider ferric carboxymaltose (FCM) as a preferred option due to its ability to replace iron deficits with 1 or 2 infusions, as recommended by recent clinical practice updates 1. When calculating the iron dose, it's essential to estimate the patient's iron stores, typically around 500 mg for adults. The choice of IV iron preparation depends on several factors, including the urgency of iron repletion, patient convenience, cost considerations, and comorbidities. Some key points to consider when selecting an IV iron preparation include:

• Ferric carboxymaltose (FCM) allows for higher doses (up to 1000 mg per infusion) with fewer visits, and has been shown to be safe and efficacious across various conditions associated with iron lack 1.
• Iron sucrose is typically given as 200-300 mg per session, requiring multiple visits.
• Iron dextran can be administered as total dose infusion but carries a higher risk of hypersensitivity reactions, and a test dose should always be performed due to anaphylaxis risk.
• Ferumoxytol and iron isomaltoside also allow for larger single doses. It's crucial to monitor patients during infusion for hypersensitivity reactions and follow institutional protocols for infusion rates. After completing the iron course, reassess iron parameters (ferritin, transferrin saturation) 4-8 weeks later to evaluate treatment efficacy.

From the FDA Drug Label

2 DOSAGE AND ADMINISTRATION

1. 1 Recommended Dosage Recommended Dosage for Treatment of Iron Deficiency Anemia For patients weighing 50 kg or more, the recommended dosage is: Injectafer 750 mg intravenously in two doses separated by at least 7 days for a total cumulative dose of 1,500 mg of iron per course In adult patients, Injectafer 15 mg/kg body weight up to a maximum of 1,000 mg intravenously may be administered as a single-dose per course. For patients weighing less than 50 kg, the recommended dosage is Injectafer 15 mg/kg body weight intravenously in two doses separated by at least 7 days per course

To calculate the iron dose for a patient requiring intravenous (IV) iron infusions, you can use the following guidelines:

• For patients weighing 50 kg or more, the recommended dosage is 750 mg intravenously in two doses separated by at least 7 days for a total cumulative dose of 1,500 mg of iron per course.
• For adult patients, the recommended dosage is 15 mg/kg body weight up to a maximum of 1,000 mg intravenously as a single-dose per course.
• For patients weighing less than 50 kg, the recommended dosage is 15 mg/kg body weight intravenously in two doses separated by at least 7 days per course. The type of iron preparation recommended is ferric carboxymaltose (Injectafer) 2.

From the Research

Calculating Iron Dose

To calculate the iron dose for a patient requiring intravenous (IV) iron infusions, the following steps can be taken:

• Calculate the total iron deficit using a modified Ganzoni formula, as suggested by 3
• The average iron deficit was calculated to be 1531 mg for patients in one study and 1392 mg for patients in another study, as reported in 3
• A total cumulative dose of 1000 mg of IV iron may be insufficient for iron repletion in a majority of patients with iron deficiency anemia (IDA), and a dose of 1500 mg is closer to the actual iron deficit in these patients, as found in 3

Choosing the Type of Iron Preparation

The following types of iron preparations can be considered:

• Ferric carboxymaltose (FCM), which allows for controlled delivery of iron to target tissues and is effective in the treatment of iron-deficiency anemia, as reported in 4
• Iron sucrose (IS), which can be administered intravenously and is effective in replenishing depleted iron stores, as found in 3 and 4
• Low molecular weight iron dextran, which can administer the patient's total iron requirement in a single infusion, as suggested by 5
• Ferric carboxymaltose is generally well tolerated, with a low risk of hypersensitivity reactions, as reported in 6

Administration Considerations

The following administration considerations should be taken into account:

• Ferric carboxymaltose can be administered intravenously in a minimum administration time of ≤15 minutes, as reported in 4
• The total iron concentration in the serum increases rapidly in a dose-dependent manner after intravenous administration of ferric carboxymaltose, as found in 4
• Repeated weekly administration of ferric carboxymaltose does not result in accumulation of transferrin iron in patients with iron-deficiency anemia, as reported in 4
• Intravenous iron therapy is reserved for iron deficiency anemia patients with intolerance or unresponsiveness to oral iron, as stated in 7