What is the best iron supplement to prescribe for anemia?

Best Iron Supplementation for Anemia

Ferrous sulfate is the preferred iron formulation for treating iron deficiency anemia due to its effectiveness, lower cost, and no evidence of superiority of other formulations. 1

First-Line Treatment: Oral Iron

Recommended Formulation

• Ferrous sulfate is the first-line treatment and preferred formulation 1, 2
• Standard dosage: 50-100 mg of elemental iron daily (equivalent to one 200 mg tablet of ferrous sulfate) 2
• No single iron formulation has proven advantages over others in terms of effectiveness 1, 2

Optimal Administration

• Give oral iron once daily at most, not multiple times per day 1
• Every-other-day dosing may be better tolerated with similar absorption rates 1, 2
• Take with vitamin C (250-500 mg) to improve absorption 1, 2
• Take on an empty stomach if tolerated; if not, can be taken with meals 1
• Avoid taking with tea or coffee (powerful inhibitors of iron absorption) 1

Treatment Duration

• After hemoglobin normalization, continue iron therapy for an additional 2-3 months to replenish iron stores 2
• Monitor hemoglobin every 4 weeks until normalization (expect a rise of 2 g/dL after 3-4 weeks) 2
• An increase in hemoglobin of at least 2 g/dL within 4 weeks is considered an acceptable response 1

When to Consider Intravenous Iron

Intravenous iron should be considered in the following situations:

1. Intolerance to oral iron despite dosage adjustments 1, 2
2. Failure to improve ferritin levels with oral therapy 1, 2
3. Conditions where oral iron absorption is impaired:
   • Active inflammatory bowel disease 1
   • Post-bariatric surgery 1
   • Patients on proton pump inhibitors 3
4. Hemoglobin below 10 g/dL requiring rapid correction 1, 2
5. Patients needing erythropoiesis-stimulating agents 1

IV Iron Formulations

• Formulations that can replace iron deficits with 1-2 infusions are preferred 1
• Options include ferric carboxymaltose (Injectafer), which can be administered as:
  • 750 mg in two doses separated by at least 7 days (for patients ≥50 kg) 4
  • 15 mg/kg up to 1,000 mg as a single dose 4

Common Pitfalls and Considerations

1. Dosing errors: Higher doses of oral iron (>100 mg elemental iron daily) do not improve absorption but increase side effects 1, 2

2. Inadequate duration: Failing to continue treatment for 2-3 months after hemoglobin normalization prevents replenishment of iron stores 2

3. Overlooking drug interactions:

   • Proton pump inhibitors significantly reduce iron absorption (only 16% of patients on omeprazole had normal hemoglobin response) 3
   • Consider IV iron or higher doses for longer duration in patients on PPIs 3

4. Ignoring side effects: Gastrointestinal side effects (constipation 12%, diarrhea 8%, nausea 11%) often lead to poor adherence 1, 5

   • Consider every-other-day dosing or taking with small meals to improve tolerance 1, 2

5. Misinterpreting response:

   • Expect hemoglobin to increase by 1 g/dL within 2 weeks of supplementation 1
   • If no improvement after 1 month in adherent patients, consider IV iron 1

6. Safety concerns with IV iron:

   • True anaphylaxis is very rare 1
   • Most reactions are complement activation-related pseudo-allergy (infusion reactions) 1
   • Monitor for 30 minutes after administration 4

By following these evidence-based recommendations, clinicians can effectively treat iron deficiency anemia while minimizing side effects and maximizing patient outcomes in terms of morbidity, mortality, and quality of life.