What is the recommended intravenous iron sucrose dosing regimen for iron‑deficiency anemia in pregnancy?

Intravenous Iron Sucrose Dosing for Iron‑Deficiency Anemia in Pregnancy

For pregnant women with iron‑deficiency anemia, administer iron sucrose 200 mg intravenously on alternate days until the calculated total dose is delivered, typically requiring 5–10 infusions (1000–2000 mg total) over 2–4 weeks. 1, 2

Standard Dosing Regimen

• Each dose is 200 mg of elemental iron, the maximum single dose permitted for iron sucrose, given as an undiluted IV push over 10 minutes. 1, 2
• Doses are administered on alternate days (not daily) to allow for adequate iron incorporation and minimize adverse effects. 1, 3
• No test dose is required before starting iron sucrose therapy, unlike iron dextran formulations. 1

Calculating Total Iron Requirement

Use the Ganzoni formula to determine the cumulative dose needed:

Total iron deficit (mg) = Body weight (kg) × [Target Hb – Actual Hb (g/dL)] × 0.24 + 500 mg 2

• The 500 mg accounts for iron store repletion. 2
• For hemoglobin < 7 g/dL, add an additional 500 mg to the calculated total. 2

Simplified Weight‑Based Approach (for patients ≥ 50 kg):

Hemoglobin Level	Total Iron Sucrose Dose	Number of 200 mg Infusions
10–12 g/dL (women) or 10–13 g/dL (men)	1000–1500 mg	5–7 infusions
7–10 g/dL	1500–2000 mg	7–10 infusions
< 7 g/dL	2000–2500 mg	10–12 infusions

2

Administration Protocol

• Dilution is not required; iron sucrose 200 mg can be given as a slow IV push over 10 minutes. 1
• Resuscitation equipment must be immediately available during every infusion, although serious hypersensitivity reactions are extremely rare (< 1:200,000 administrations). 1, 2
• Administer doses every other day until the total calculated requirement is met. 1, 3

Expected Hematologic Response

• Reticulocyte count rises within 3–5 days of starting therapy, peaking at 2 weeks. 4
• Hemoglobin should increase by ≥ 2 g/dL within 4 weeks after completing the full course. 1, 2, 5, 3
• Serum ferritin should rise to > 30 ng/mL by 4 weeks, confirming iron store repletion. 5, 3, 4

Monitoring Schedule

• Baseline: Hemoglobin, mean corpuscular volume (MCV), serum ferritin, and transferrin saturation. 5, 3
• During therapy: Hemoglobin and reticulocyte count at days 7,14, and 28. 5, 3
• Post‑therapy: Recheck hemoglobin and ferritin 4 weeks after the final infusion (not earlier, as circulating iron interferes with assays). 1, 2
• At delivery: Confirm hemoglobin ≥ 11 g/dL and ferritin ≥ 30 ng/mL. 5, 3

Safety Profile in Pregnancy

• FDA Pregnancy Category: Published studies after the first trimester show no adverse maternal or fetal outcomes. 6
• Common maternal side effects include mild arthralgia, transient hypotension, and injection‑site reactions; serious adverse events are rare. 1, 6, 5
• Fetal considerations: Severe maternal hypersensitivity reactions (e.g., anaphylaxis, circulatory collapse) can cause fetal bradycardia, particularly in the second and third trimesters, though such events are exceedingly rare. 6
• Neonatal outcomes (birth weight, Apgar scores, preterm delivery rates) are comparable to oral iron therapy. 5, 3, 7

Absolute Contraindications

• Active bacteremia or uncontrolled infection—withhold iron sucrose until the infection is resolved. 1, 2
• Hemoglobin > 15 g/dL or evidence of iron overload (ferritin > 800 μg/L, transferrin saturation > 50%). 2
• Known hypersensitivity to iron sucrose or any excipient. 6

Common Pitfalls & How to Avoid Them

1. Stopping therapy prematurely: The most frequent error is discontinuing after 2–3 doses when 5–10 infusions are needed to fully replete iron stores. Always calculate the total deficit before starting. 2
2. Rechecking iron studies too early: Do not measure ferritin or transferrin saturation within 4 weeks of the last infusion, as falsely elevated values will mislead management. 1, 2
3. Concurrent oral iron: Do not prescribe oral iron simultaneously with IV therapy; it does not enhance efficacy and increases gastrointestinal side effects. 2
4. Inadequate observation: Although hypersensitivity is rare, ensure resuscitation equipment is present and observe the patient for at least 30 minutes after each infusion. 1, 2

Comparison with Oral Iron in Pregnancy

• Hemoglobin rise: IV iron sucrose increases hemoglobin by 3.1–5.1 g/dL over 4 weeks versus 1.3–3.1 g/dL with oral ferrous sulfate. 5, 3, 7
• Time to target Hb ≥ 11 g/dL: IV therapy achieves this in 6.9 weeks versus 14.9 weeks with oral iron. 8
• Ferritin repletion: IV iron sucrose raises ferritin to 37–69 ng/mL at 4 weeks versus 14 ng/mL with oral therapy. 3, 4
• Tolerability: Oral iron causes gastrointestinal side effects in 30–36% of patients and poor compliance in 10–30%, whereas IV iron sucrose has minimal side effects. 5, 3, 8

When to Choose IV Iron Sucrose Over Oral Therapy

• Hemoglobin < 10 g/dL in the second or third trimester, when rapid correction is needed before delivery. 3, 4
• Failure to respond to oral iron after 4 weeks of adherent therapy (ferritin remains < 15 ng/mL). 2
• Intolerance to oral iron (nausea, constipation, diarrhea). 1, 8
• Active inflammatory bowel disease, where hepcidin elevation impairs oral iron absorption. 1
• Presentation late in pregnancy (≥ 28 weeks), when insufficient time remains for oral therapy to correct anemia. 3, 7

Advantages of Iron Sucrose Over Newer IV Formulations in Pregnancy

• Lower hypophosphatemia risk: Iron sucrose causes clinically significant hypophosphatemia in only ≈ 1% of patients, compared to 58% with ferric carboxymaltose. 1
• Established safety data in pregnancy: Multiple randomized trials confirm safety after the first trimester, whereas newer agents have less robust pregnancy‑specific evidence. 6, 5, 3, 8, 7
• Lower cost: Iron sucrose has a significantly lower acquisition cost than ferric carboxymaltose, though it requires more clinic visits. 9, 1

Management of Inadequate Response

If hemoglobin fails to rise by ≥ 2 g/dL at 4 weeks:

• Investigate ongoing blood loss (e.g., placental abruption, gastrointestinal bleeding). 1, 2
• Rule out other causes of anemia: Folate or B12 deficiency, hemoglobinopathy, chronic disease, malignancy. 1, 2
• Confirm iron repletion: Verify ferritin > 30 ng/mL and transferrin saturation > 20%. 2
• Consider additional iron doses only if ferritin remains < 30 ng/mL. 2