Parenteral Iron

Introduction

In iron deficiency anaemia management, there are a number of settings in which the use of intravenous iron may be preferable to oral iron.

  • Poor adherence or gastrointestinal side effects of oral iron.
  • Prefer to replete iron stores in 1 or 2 visits rather than over the course of several months.
  • Ongoing blood loss that exceeds the capacity of oral iron to meet needs (heavy uterine bleeding, mucosal telangiectasias).
  • Anatomic or physiologic condition that interferes with oral iron absorption.
  • Coexisting inflammatory state that interferes with iron homeostasis.

Parenteral iron may also reduce the use of blood transfusion, which in turn avoids transfusion-associated risks.

NOTE: IV iron is contraindicated in the first trimester of pregnancy.



Choice of IV Formulation

A number of IV iron formulations are available, including ferric carboxymaltose, ferric gluconate, ferumoxytol, iron sucrose, ferric derisomaltose (previously termed iron isomaltoside), and low molecular weight iron dextran.

IV Iron Products

NOTE: High molecular weight iron dextran has a greater frequency of allergic reactions and is no longer available.

All formulations are equally effective in treating iron deficiency and have a similar safety profile. Major differences include

  • Cost
  • Formulary/purchasing agreements
  • Number of visits/times required to administer the full dose

NOTE: Ferric carboxymaltose, ferumoxytol, ferric derisomaltose (previously termed iron isomaltoside) and low molecular weight iron dextran can be administered as a single dose.



Dose Calculation

The cumulative dose calculation for parenteral iron is based on patient's body weight and target haemoglobin level.

  • The patient's total body iron deficit is NOT the same as the allowable iron dose per infusion which is DIFFERENT for each product.

Ganzoni Formula

Total Body Iron Deficit (mg) = [Body Weight (kg) * (Target Hb - Actual Hb) (g/dL) * 2.4] + Iron Depot (mg)
  • Use Ideal Body Weight for obese patients or pre-pregnancy weight for pregnant women.
  • Iron Depot = Use 500 mg for adults and children ≥35 kg; use 15 mg/kg if <35 kg.

In cases of iron replacement secondary to blood loss and to support autologous blood donation, formula assumes that the storage iron does not need to be restored.

Iron to be Replaced (mg) = Body Weight (kg) * (Target Hb - Actual Hb) (g/dL) * 2.4



Intramuscular

Intramuscular (IM) iron is available and will raise the iron level, but this route of administration is painful, stain the buttocks and has variable absorption.



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