How to improve hemoglobin levels in a pregnant patient allergic to oral iron?

Management of Anemia in Pregnancy with Oral Iron Intolerance

Intravenous iron is the definitive treatment for this patient with severe anemia (Hb 8 g/dL) at 30 weeks gestation who cannot tolerate oral iron formulations. 1

Immediate Treatment Recommendation

Administer intravenous ferric carboxymaltose (FCM) or iron isomaltoside, which allow high-dose iron repletion (500-1000 mg) in a single 15-minute infusion. 1, 2, 3

Specific IV Iron Dosing for This Patient

• For hemoglobin 7-10 g/dL with body weight ≥70 kg: Total iron dose needed is 2000 mg 1
• For hemoglobin 7-10 g/dL with body weight <70 kg: Total iron dose needed is 1500 mg 1
• Ferric carboxymaltose can be given as 750-1000 mg per infusion, repeated after 7 days if needed to reach total dose 2
• Iron isomaltoside can deliver up to 20 mg/kg (approximately 1000-1500 mg) in a single infusion 1

Why IV Iron is Superior in This Clinical Context

• Oral iron is ineffective when the patient has documented intolerance/allergy to all oral formulations including gummies 1
• Severe anemia (Hb 8 g/dL) at 30 weeks gestation requires rapid correction to prevent maternal and fetal complications 2, 4
• IV iron bypasses gastrointestinal absorption, which is the limiting factor in oral iron therapy 5
• Expected hemoglobin increase of 1-2 g/dL within 2-4 weeks with IV iron 6, 2

Safety Considerations for IV Iron in Pregnancy

IV iron formulations (ferric carboxymaltose, iron isomaltoside, iron sucrose) are safe in the second and third trimesters of pregnancy. 7, 8

Risk Mitigation Strategies

• Administer in a facility with resuscitation capabilities, as required by regulatory agencies 7, 5
• True anaphylaxis is very rare (affecting <1% of patients), but complement-mediated infusion reactions can occur in approximately 1 in 200 patients 7, 8
• Avoid rapid infusion rates, as fast infusion is a major risk factor for hypersensitivity reactions 7
• Monitor for hypophosphatemia with ferric carboxymaltose, which affects 50-74% of patients and can cause bone complications 3, 4
• Early pregnancy (first trimester) is a contraindication to IV iron, but this patient is at 30 weeks 7

Monitoring and Follow-Up

Check hemoglobin at 2-4 weeks to assess response to IV iron therapy. 1, 6

• Expected hemoglobin rise of approximately 2 g/dL after 3-4 weeks of treatment 6
• Monitor serum ferritin and transferrin saturation to confirm iron store repletion 2
• Target ferritin levels should not exceed 500-800 μg/L to avoid potential iron overload 1
• After delivery and correction of anemia, monitor blood count every 6 months initially to detect recurrence 1

Alternative Considerations (If IV Iron Unavailable)

If IV iron is absolutely unavailable, consider packed red blood cell transfusion for symptomatic severe anemia, though this should be restricted and used only when necessary. 1

• Transfusion may be required if the patient is symptomatic (dyspnea, tachycardia, chest pain) or if hemoglobin drops further 1
• However, transfusion does not replete iron stores and should be followed by IV iron when available 1

Common Pitfalls to Avoid

• Do not delay IV iron therapy waiting for further investigations—treatment should not be deferred 1
• Do not attempt alternative oral iron formulations (ferric maltol, polysaccharide iron) in a patient with documented allergy to all oral iron preparations 1
• Do not use intramuscular iron, which is obsolete due to painful injections, tissue damage, and unacceptable side effects 1
• Do not use iron dextran as first-line IV iron, as it requires a test dose due to higher risk of serious anaphylactic reactions 1

Regarding the Intrahepatic Cholestasis Component

The serum bile acid of 14 μmol/L and ursodeoxycholic acid (Udiliv) therapy are appropriate for intrahepatic cholestasis of pregnancy management, but this does not affect iron therapy decisions. The anemia must be addressed independently with IV iron as outlined above.