What are the absolute indications for intravenous (IV) iron supplementation in patients with severe iron deficiency anemia, particularly those with chronic kidney disease, inflammatory bowel disease, or a history of gastrointestinal bleeding?

Absolute Indications for Intravenous Iron

Intravenous iron should be used as first-line therapy in patients with inflammatory bowel disease and active inflammation with compromised absorption, hemoglobin below 10 g/dL, previous intolerance to oral iron, or when oral iron fails to improve ferritin levels after an adequate trial. 1, 2

Primary Absolute Indications

Inflammatory Bowel Disease (IBD)

• Active IBD with clinically active disease and compromised iron absorption 1
• Hemoglobin below 10 g/dL (severe anemia) regardless of disease activity 1, 2
• Previous intolerance to oral iron 1
• Patients requiring erythropoiesis-stimulating agents 1

The American Gastroenterological Association (AGA) and European Crohn's and Colitis Organization (ECCO) both emphasize that IV iron is more effective, shows faster response, and is better tolerated than oral iron in IBD patients. 1, 2 This is particularly important because oral iron may exacerbate disease activity and alter intestinal microbiota in IBD. 1

Chronic Kidney Disease (CKD)

• Patients on hemodialysis with ongoing iron losses 2
• Oral iron fails to meet iron status targets 2
• Oral iron not tolerated 2

For CKD patients on dialysis (stage 5D), IV iron is the preferred method of supplementation. 3

Malabsorptive Conditions

• Post-bariatric surgery patients (particularly procedures disrupting duodenal iron absorption) with iron deficiency anemia and no identifiable chronic GI blood loss 1, 2
• Celiac disease patients who fail to improve iron stores despite adherence to gluten-free diet and oral iron supplementation 1, 2

Failure of Oral Iron Therapy

• Ferritin levels do not improve after an adequate trial of oral iron 1
• Conditions where oral iron absorption is compromised 1
• Intolerance to oral iron (gastrointestinal side effects) 1

Disease-Specific Considerations

Portal Hypertensive Gastropathy

• IV iron should be used in patients with ongoing bleeding who do not respond to oral iron therapy 1
• Initial management should attempt oral iron supplementation first 1

Heart Failure

• Iron deficiency in heart failure patients (NYHA class II/III) to improve exercise capacity, even without anemia 2, 4
• Dosing is based on hemoglobin levels and body weight, 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

Dosing Guidelines for IBD

The ECCO guidelines provide specific dosing based on hemoglobin and body weight: 1

• Hemoglobin 10-12 g/dL (women) or 10-13 g/dL (men):

  • Body weight <70 kg: 1000 mg total
  • Body weight ≥70 kg: 1500 mg total

• Hemoglobin 7-10 g/dL:

  • Body weight <70 kg: 1500 mg total
  • Body weight ≥70 kg: 2000 mg total

Practical Implementation

Preferred Formulations

• Use IV iron formulations that can replace iron deficits with 1 or 2 infusions rather than those requiring more than 2 infusions 1, 2
• Ferric carboxymaltose allows single doses up to 1,000 mg administered over 15 minutes 1, 2
• Iron sucrose is limited to 200-300 mg per treatment episode with repeated dosing 1

Safety Considerations

• All IV iron formulations have similar risks; true anaphylaxis is very rare 1, 2
• Most reactions are complement activation-related pseudo-allergy (infusion reactions), not true anaphylaxis 1
• Test doses are required only for iron dextran preparations due to anaphylactic risk 1
• Avoid iron overload: transferrin saturation >50% and ferritin >800 μg/L should be upper limits 1

Monitoring and Re-treatment

Follow-up Monitoring

• Monitor IBD patients every 3 months for at least one year after correction, then every 6-12 months thereafter 1
• Check serum phosphate levels in patients requiring repeat courses within 3 months 4

Re-treatment Criteria

• Re-initiate IV iron when ferritin drops below 100 μg/L or hemoglobin below 12-13 g/dL (according to gender) 1
• Target post-treatment ferritin levels of 400 μg/L to prevent recurrence within 1-5 years 1

Common Pitfalls to Avoid

• Do not use oral iron in patients with active IBD as it may worsen inflammation and disease activity 1
• Do not delay IV iron in severe anemia (hemoglobin <10 g/dL) while attempting oral therapy 1
• Do not use intramuscular iron as it is obsolete, painful, and associated with unacceptable side effects 1
• Recognize that recurrent anemia may indicate persistent intestinal disease activity even with normal inflammatory markers 1