What is the recommended regimen for iron infusion in patients with iron deficiency anemia?

Iron Infusion Regimens for Iron Deficiency Anemia

For patients ≥50 kg with iron deficiency anemia, administer a total cumulative dose of 1500 mg of intravenous iron, as this more accurately matches the calculated iron deficit and reduces retreatment requirements compared to the commonly underdosed 1000 mg regimen. 1

Calculating Total Iron Deficit

The actual iron deficit in most IDA patients averages 1392-1531 mg, not the 1000 mg commonly prescribed 1. Use either:

Simplified Dosing Approach (Preferred):

• Hb 10-12 g/dL (women) or 10-13 g/dL (men): 1000-1500 mg total 2
• Hb 7-10 g/dL: 1500-2000 mg total 2
• Hb <7 g/dL: Add 500 mg to above calculations 3, 2

Ganzoni Formula (Alternative):

• Body weight (kg) × [target Hb - actual Hb (g/dL)] × 0.24 + 500 mg 3, 2
• Note: This formula is prone to error, underestimates requirements, and is inconsistently used in practice 3

Specific Product Regimens

Ferric Carboxymaltose (Injectafer) - First-Line Choice

For patients ≥50 kg:

• 750 mg IV × 2 doses separated by ≥7 days (total 1500 mg per course) 4
• Alternative: Single dose of 1000 mg IV (15 mg/kg up to 1000 mg maximum) 4
• Infusion time: 15 minutes minimum 4

For patients <50 kg:

• 15 mg/kg IV × 2 doses separated by ≥7 days 4

This formulation allows high-dose administration (up to 1000 mg per infusion) with minimal infusion time, reducing clinic visits 3, 5

Iron Sucrose (Venofer) - Alternative

Standard regimen:

• 200 mg IV per dose, maximum single dose 3, 2
• For 1000 mg total: 5 doses over 14 days 2
• For 1500 mg total: 7-8 doses 2
• For 2000 mg total: 10 doses 2
• Infusion time: 10 minutes per 200 mg dose 2

Iron sucrose requires multiple visits due to dose limitations but has extensive safety data 3, 6

Low Molecular Weight Iron Dextran (INFeD)

• Can deliver >1000 mg by total dose infusion 3
• Requires mandatory test dose due to anaphylaxis risk 3
• Reserved for situations requiring single large-dose administration 3

Clinical Context-Specific Recommendations

Inflammatory Bowel Disease

Intravenous iron is first-line (not oral) for: 3

• Clinically active IBD
• Previous oral iron intolerance
• Hemoglobin <10 g/dL
• Patients requiring erythropoiesis-stimulating agents

Chronic Kidney Disease

• Iron sucrose: 200-300 mg per treatment episode, repeated dosing 3
• Ferric gluconate: 125 mg maximum per dose 3
• Ferumoxytol: 510 mg × 2 doses 3

Heart Failure with Iron Deficiency

Follow weight and hemoglobin-based dosing per FDA label for ferric carboxymaltose, with maintenance doses at 12,24, and 36 weeks if ferritin <100 ng/mL or ferritin 100-300 ng/mL with transferrin saturation <20% 4

Administration Critical Points

Pre-infusion requirements:

• Resuscitation equipment must be immediately available 2
• No test dose required for ferric carboxymaltose, iron sucrose, or ferric gluconate 3, 4
• Dilute ferric carboxymaltose in ≤250 mL normal saline to concentration ≥2 mg iron/mL 4

Monitoring during infusion:

• Observe for at least 30 minutes post-infusion 3
• Monitor for extravasation (causes long-lasting brown discoloration) 4

Response Assessment

At 4 weeks post-treatment: 3, 2

• Recheck hemoglobin, ferritin, and transferrin saturation
• Expected response: Hemoglobin increase ≥2 g/dL within 4 weeks 3
• If target not achieved, investigate ongoing blood loss or other causes 2

Retreatment considerations:

• Patients receiving 1500 mg ferric carboxymaltose require significantly less retreatment (5.6%) compared to 1000 mg iron sucrose (11.1%, p<0.001) between days 56-90 1
• Check serum phosphate before repeat courses, especially if within 3 months 4

Critical Pitfalls to Avoid

The most common error is premature discontinuation after 2-3 doses when 5+ doses are needed to fully replete iron stores 2. Additional pitfalls:

• Never administer during active bacterial infection 3 - iron promotes bacterial growth
• Do not combine with oral iron 2 - no additional benefit and increases side effects
• Do not exceed transferrin saturation >50% or ferritin >800 μg/L 2 - risk of iron overload
• Monitor for hypophosphatemia with ferric carboxymaltose (affects 50-74% of patients) 7 - can cause bone pain, osteomalacia, and fractures
• Avoid rapid infusion of ferumoxytol 3 - associated with increased infusion reactions

Safety Profile

Modern IV iron formulations have anaphylaxis risk <1:200,000 administrations 3. The most common reaction is complement-activated related pseudo-allergy (CARPA/Fishbane reaction), not true anaphylaxis 3. Common mild-moderate adverse events include headache, dizziness, nausea, and injection-site reactions 5.