Ferric Carboxymaltose (FCM)

What It Is

Mechanism & Pharmacology

• The iron is encased in a carboxymaltose carbohydrate shell, which allows slow, controlled release to the reticuloendothelial system (macrophages in liver, spleen, bone marrow).
• Unlike high-molecular-weight iron dextran (which carries significant anaphylaxis risk), FCM has a much lower adverse reaction profile.
• Delivers 750 mg of elemental iron per infusion — one of the highest single-dose capabilities among IV iron products. (Harrison's, p. 2893)

Comparison with Other IV Iron Products

Key Indications

1. Iron Deficiency Anemia (IDA)

• First-line IV iron when oral iron fails (intolerance, malabsorption, inflammatory bowel disease, post-bariatric surgery, chronic kidney disease on EPO).
• EPO therapy creates high iron demand that oral iron frequently cannot meet — IV iron including FCM bridges this gap. (Harrison's, p. 2893)

2. Heart Failure with Iron Deficiency

• The FAIR-HF trial (iron sucrose or FCM) and CONFIRM-HF trial (FCM specifically) demonstrated that FCM corrects anemia and improves:
  • Functional capacity (6-minute walk test, NYHA class)
  • Symptoms and quality of life
• Patient criteria used: ferritin <100 ng/mL, or ferritin 100–300 ng/mL if transferrin saturation <20%.
• Oral iron is not effective in heart failure with iron deficiency.
• Erythropoiesis-stimulating agents (e.g., darbepoetin — RED-HF trial) have shown disappointing results in HF, making FCM a preferred option. (Harrison's, p. 7196)

3. Chronic Kidney Disease (CKD) / Dialysis

• Standard of care alongside EPO in dialysis-dependent CKD.

4. Perioperative / Preoperative Anemia Optimization

• Used to build iron stores before elective surgery to reduce allogeneic transfusion.

Dosing

• Administered as a slow IV infusion or IV push (depending on protocol).
• Up to 750 mg per dose, which can be repeated at intervals (typically ≥7 days apart) to reach the calculated total iron deficit (using the Ganzoni formula or product labeling).
• Two-dose regimen (750 mg × 2, separated by ≥7 days) = maximum 1500 mg per course.

Safety & Adverse Effects

Common / Mild

• Nausea, flushing, headache, dizziness, injection site reactions.

Clinically Important: Hypophosphatemia

• FCM is the IV iron most strongly associated with transient but sometimes severe hypophosphatemia, mediated by FGF-23 (fibroblast growth factor 23) elevation.
• This can be clinically significant in patients with pre-existing phosphate depletion (e.g., malnutrition, renal tubular disease).
• Ferric derisomaltose has a lower FGF-23-mediated phosphate effect in comparative trials (PHOSPHARE trials).

Hypersensitivity Reactions

• Rare with FCM compared to high-molecular-weight iron dextran; however, serious hypersensitivity/anaphylactic reactions can still occur — resuscitation equipment should be available.

Hypotension

• Can occur during rapid infusion.

Contraindications

• Known hypersensitivity to FCM or any component.
• Hemochromatosis or other iron overload states.
• Non-iron-deficiency anemias.

Clinical Pearl