In an adult male with ferritin 15.4 ng/mL, how many Injectefer (ferric carboxymaltose) infusions are needed?

Ferric Carboxymaltose (Injectafer) Dosing for Adult Male with Ferritin 15.4 ng/mL

An adult male with ferritin 15.4 ng/mL requires a total cumulative dose of 1,500 mg of ferric carboxymaltose, administered as two 750 mg infusions separated by at least 7 days. 1

FDA-Approved Dosing Regimen

For patients weighing 50 kg or more with iron deficiency anemia, the standard FDA-approved regimen is:

• 750 mg intravenously on Day 1
• 750 mg intravenously on Day 8 or later (minimum 7-day interval)
• Total cumulative dose: 1,500 mg per course 1

Alternatively, a single-dose regimen of 15 mg/kg body weight (maximum 1,000 mg) may be administered, but this frequently results in underdosing and residual iron deficiency. 1, 2

Why Two Infusions Are Required

A single 1,000 mg infusion is insufficient for most patients and leads to dose deficits. 2 In a retrospective analysis of 211 heart failure patients with iron deficiency, 61% required doses exceeding 1,000 mg to achieve adequate iron repletion, with calculated target doses averaging 1,308 mg. 2 Patients receiving inadequate doses had:

• 4.93 times higher odds of residual iron deficiency with a 500 mg dose deficit 2
• 7.78 times higher odds of residual iron deficiency with a 1,000 mg dose deficit 2
• Less symptomatic and biochemical improvement 2

Administration Protocol

Each 750 mg infusion should be prepared and administered as follows:

• Dilute up to 750 mg in no more than 250 mL of 0.9% sodium chloride (minimum concentration 2 mg iron/mL) 1
• Infuse over at least 15 minutes 1
• Alternatively, administer as undiluted slow IV push at approximately 100 mg (2 mL) per minute 1
• Observe patient for at least 30 minutes post-infusion for hypersensitivity reactions 1, 3

Critical Safety Considerations

Before administering ferric carboxymaltose, verify the following contraindications:

• Do not administer if hemoglobin >15 g/dL 1, 3
• Avoid in patients with active bacteremia or infection 3
• Check for hypersensitivity to ferric carboxymaltose or other parenteral iron products 1
• Measure baseline serum phosphate, as ferric carboxymaltose causes hypophosphatemia in 58% of patients (compared to 4% with iron derisomaltose and 1% with iron sucrose) 3, 4

Monitoring and Reassessment

After completing the two-dose course:

• Wait 4–8 weeks before rechecking iron parameters (ferritin, transferrin saturation, complete blood count), as earlier testing yields falsely elevated ferritin levels 3
• Expect hemoglobin to increase by 1–2 g/dL within 4–8 weeks 3
• Reassess iron status at 3 months to determine if additional therapy is needed 3
• If ferritin remains <100 µg/L or ferritin is 100–300 µg/L with transferrin saturation <20%, administer maintenance doses of 500 mg at 12,24, and 36 weeks 1

Common Pitfall: Single-Dose Underdosing

The most common error is administering only one 1,000 mg infusion and assuming iron repletion is complete. 2 This approach leaves the majority of patients with residual iron deficiency, requiring additional clinic visits and repeat infusions. 2 The FDA-approved two-dose regimen of 750 mg × 2 (total 1,500 mg) is specifically designed to achieve adequate iron stores in most patients. 1

Hypophosphatemia Monitoring

Check serum phosphate levels in patients requiring repeat courses within 3 months, as ferric carboxymaltose has the highest hypophosphatemia rate among IV iron formulations. 1, 3, 4 Most cases are asymptomatic and resolve without intervention, but symptomatic hypophosphatemia should be treated as medically indicated. 1, 3