What is the recommended dosing of Ferric Carboxymaltose (Iron replacement therapy) for a 30-year-old female patient with severe iron deficiency anemia, weighing 50kg, with a hemoglobin level of 7 g/dL and a ferritin level of 20 ng/mL?

Ferric Carboxymaltose Dosing for 30-Year-Old Female with Severe Iron Deficiency Anemia

For this patient weighing 50 kg with hemoglobin 7 g/dL and ferritin 20 ng/mL, administer ferric carboxymaltose 750 mg intravenously on Day 1, followed by a second dose of 750 mg at least 7 days later, for a total cumulative dose of 1,500 mg of iron per course. 1

Specific Dosing Protocol

For patients weighing exactly 50 kg or more, the FDA-approved dosing is 750 mg IV × 2 doses separated by at least 7 days (total 1,500 mg). 1 This patient meets the weight threshold precisely.

Alternative Single-Dose Option

• A single dose of 750 mg (15 mg/kg × 50 kg = 750 mg) can be administered as a one-time infusion per course, though the two-dose regimen provides more complete iron repletion for severe anemia. 1

Administration Details

Dilute each 750 mg dose in 100-250 mL of normal saline (0.9% NaCl) to achieve a concentration of at least 2 mg iron/mL, and infuse over at least 15 minutes. 2, 1

Step-by-Step Administration:

• Mix 750 mg FCM in 100-250 mL normal saline (concentration must be ≥2 mg/mL for stability). 1
• Infuse over 15-30 minutes through a secure IV line. 2, 1
• Observe the patient for at least 30 minutes post-infusion for hypersensitivity reactions. 2, 1
• Ensure proper IV placement to avoid extravasation, which causes long-lasting brown skin discoloration. 1

Rationale for This Dosing

With hemoglobin of 7 g/dL, this patient has severe iron deficiency anemia requiring rapid correction that oral iron cannot provide. 2 The ferritin of 20 ng/mL confirms absolute iron deficiency (ferritin <100 ng/mL). 3

FCM allows administration of high iron doses (up to 1,000 mg per infusion) over short timeframes (15 minutes), making it ideal for severe anemia. 2, 4 The 1,500 mg total dose typically restores iron stores to normal in patients with iron deficiency anemia. 2

Expected Response Timeline

Reticulocytosis occurs at 3-5 days post-administration. 2 Hemoglobin should increase by 1-2 g/dL within 4-8 weeks of therapy, with increases beginning within 1-2 weeks. 2, 4, 5

Mean hemoglobin increase is approximately 2.4 g/dL at one month following FCM treatment. 5 Given her baseline of 7 g/dL, expect hemoglobin to reach approximately 9-10 g/dL after the complete course.

Monitoring Requirements

Check complete blood count (CBC) and iron parameters (ferritin, transferrin saturation) 4-8 weeks after the last infusion—NOT before 4 weeks. 2 Checking iron parameters within 4 weeks yields falsely elevated ferritin levels that cannot accurately reflect iron status. 2, 6

Follow-up Laboratory Testing:

• CBC at 4-8 weeks post-treatment to assess hemoglobin response. 2
• Ferritin and transferrin saturation at 4-8 weeks to confirm iron repletion. 2
• Do NOT recheck iron studies before 4 weeks as circulating iron interferes with assays. 2

Critical Safety Considerations

Contraindications to Verify Before Administration:

• Do NOT administer if hemoglobin >15 g/dL (not applicable here). 2, 1
• Do NOT administer if active bacteremia or acute infection is present. 2, 6, 1
• Do NOT administer if history of serious hypersensitivity to parenteral iron products. 2, 1
• Do NOT administer if evidence of iron overload exists (not applicable with ferritin 20 ng/mL). 2, 1

Important Warnings:

FCM causes treatment-emergent hypophosphatemia in 47-75% of patients, though most cases are asymptomatic and resolve without intervention. 2 The British Society of Gastroenterology reports hypophosphatemia rates of 58% with FCM. 2

If repeat treatment is needed within 3 months, check serum phosphate levels before and after administration. 1 Treat hypophosphatemia as medically indicated. 1

True anaphylaxis risk is very low (<0.1-1.0%), but complement activation-related pseudo-allergy (infusion reactions) can occur. 2 This is why 30-minute post-infusion observation is mandatory. 2, 1

Advantages Over Oral Iron

Oral iron is ineffective for this patient with hemoglobin 7 g/dL who requires rapid correction. 2 Oral iron typically increases hemoglobin by only 0.1-0.2 g/dL per week, meaning it would take 15-20 weeks to achieve adequate correction. 2

FCM provides complete iron repletion in 1-2 weeks with just two clinic visits, compared to months of daily oral iron with frequent gastrointestinal side effects. 2, 4

When to Consider Repeat Treatment

Reassess iron status (ferritin, transferrin saturation, hemoglobin) at 3 months after initial treatment. 2, 6 If iron deficiency recurs (ferritin <100 ng/mL or ferritin 100-299 ng/mL with transferrin saturation <20%), repeat FCM dosing can be administered. 6, 1

For repeat courses within 3 months, mandatory serum phosphate monitoring is required before and after administration. 1