What is the recommended treatment for patients with iron deficiency anemia who cannot tolerate oral iron or have severe deficiency, specifically regarding iron infusion?

Iron Infusion for Iron Deficiency Anemia

Intravenous iron should be used if the patient does not tolerate oral iron, ferritin levels do not improve with a trial of oral iron, or the patient has a condition in which oral iron is not likely to be absorbed. 1

Indications for Iron Infusion

Iron infusion is indicated in the following situations:

• Patients who cannot tolerate oral iron due to side effects 1
• Patients with inadequate response to oral iron despite good adherence 1
• Patients with conditions affecting iron absorption:
  • Inflammatory bowel disease with active inflammation 1
  • Post-bariatric surgery 1
  • Celiac disease not responding to gluten-free diet 1
• Patients with severe anemia requiring rapid correction 2
• Patients with chronic kidney disease (non-dialysis dependent) 3
• Patients with heart failure and iron deficiency to improve exercise capacity 3

Available IV Iron Formulations

Several IV iron preparations are currently available:

• Ferric carboxymaltose (Injectafer): Can be given in large doses (750 mg) with fewer infusions 3
• Iron sucrose: Maximum individual dose of 200 mg, no test dose required 1
• Ferric gluconate: Maximum individual dose of 125 mg, no test dose required 1
• Low molecular weight iron dextran: Can be given in doses >1000 mg but requires test dose due to risk of anaphylaxis 1
• Ferumoxytol: Recommended dose of 510 mg followed by a second 510 mg dose 1

Dosing and Administration

For ferric carboxymaltose (Injectafer), the FDA-approved dosing is:

• For patients ≥50 kg: 750 mg IV in two doses separated by at least 7 days (total 1,500 mg) 3
• Alternative for adults ≥50 kg: 15 mg/kg up to 1,000 mg as a single dose 3
• For patients <50 kg: 15 mg/kg IV in two doses separated by at least 7 days 3

Safety Considerations

1. Monitor for hypersensitivity reactions:

   • Observe patients for at least 30 minutes after administration 3
   • Signs include hypotension, dizziness, loss of consciousness, breathing difficulty, swelling 3

2. Monitor for hypophosphatemia:

   • Particularly important in patients requiring repeat courses 3
   • Check phosphate levels before repeat treatment if at risk 3

3. Monitor blood pressure:

   • Hypertension can occur during treatment 3
   • Check blood pressure after infusion 3

Expected Response and Follow-up

• Expect hemoglobin rise ≥10 g/L within 2 weeks of treatment 2
• Continue treatment until both hemoglobin normalization and replenishment of iron stores (target ferritin >100 μg/L) 2
• Monitor hemoglobin and red cell indices every 4 weeks until normalization 2
• Check for recurrent iron deficiency every 3 months for at least a year after correction 2

Advantages of IV Iron Over Oral Iron

• Faster correction of iron deficiency 1
• Avoids gastrointestinal side effects common with oral iron (nausea, constipation, abdominal pain) 2
• Higher compliance rates 2
• More effective in inflammatory conditions where hepcidin levels are elevated 1

Common Pitfalls and Caveats

1. Not considering IV iron early enough in patients with inflammatory conditions where oral iron absorption is impaired
2. Overestimating the risk of severe reactions with newer IV iron formulations - true anaphylaxis is very rare with modern preparations 1
3. Inadequate dosing - ensure complete iron repletion to prevent early recurrence
4. Not investigating the underlying cause of iron deficiency before treatment
5. Failure to monitor phosphate levels with repeated iron infusions 3

IV iron infusion is a safe and effective treatment for iron deficiency anemia when properly indicated and administered, with significant benefits for morbidity, mortality, and quality of life in patients who cannot use or do not respond to oral iron therapy.