Why is ferrous sulfate (iron supplement) recommended over iron bisglycinate for treating severe iron deficiency anemia?

Ferrous Sulfate vs Iron Bisglycinate for Severe Iron Deficiency Anemia

Ferrous sulfate is recommended over iron bisglycinate for treating severe iron deficiency anemia primarily due to its lower cost with similar efficacy, as there is no evidence of superiority of iron bisglycinate in clinical trials. 1

Comparative Efficacy and Cost

• Ferrous sulfate is often the first-line treatment for iron deficiency anemia due to its proven efficacy, low cost, and wide availability 2
• Ferrous sulfate costs approximately $0.30-$4.50 for 30 pills, while ferrous bisglycinate costs around $2.40 for the same quantity 1
• Clinical trials have not demonstrated that iron bisglycinate is superior to ferrous sulfate in effectiveness, despite claims of better tolerability 1
• In gastrectomized patients with iron deficiency anemia, ferrous sulfate actually showed better results in hematologic laboratory parameters than ferrous bisglycinate chelate 3

Dosing and Administration

• The recommended approach is to start with ferrous sulfate 200 mg once daily (providing 65 mg of elemental iron), as taking iron more than once daily does not improve absorption but increases side effects 1
• Ferrous sulfate should be taken on an empty stomach for optimal absorption, though some patients may better tolerate taking it with meals 1
• Adding vitamin C (80-500 mg) when taking iron can improve absorption by forming a chelate that prevents formation of insoluble iron compounds 1, 2
• Tea and coffee should be avoided within an hour of taking iron as they inhibit absorption 1

Side Effects Management

• Common side effects of oral iron include constipation (12%), diarrhea (8%), and nausea (11%) 1, 2
• While some patients may tolerate iron bisglycinate better, this potential advantage doesn't outweigh the cost difference for initial therapy 1
• Taking iron every other day may improve tolerance while maintaining effectiveness, though this approach needs further study 1
• In a study comparing ferrous bisglycinate to ferrous sulfate in cancer patients, ferrous bisglycinate showed similar efficacy with potentially lower GI toxicity (17% vs 33%), but this advantage doesn't justify its higher cost as first-line therapy 4

Treatment Monitoring and Duration

• In anemic patients, hemoglobin levels should increase by approximately 1 g/dL within 2 weeks of starting supplementation 1
• The absence of an Hb rise of at least 10 g/L after 2 weeks strongly predicts subsequent treatment failure 1
• Oral iron should be continued for 3 months after iron deficiency has been corrected to replenish stores 1, 2
• If blood counts or iron stores don't improve with oral iron, or if the patient cannot tolerate it, intravenous iron should be considered 1

Special Considerations

• For patients with severe symptoms, significant intolerance to oral iron, or conditions affecting iron absorption (bariatric surgery, active inflammatory bowel disease), IV iron may be more appropriate than oral formulations 1, 2
• In a randomized clinical trial with children, ferrous sulfate demonstrated greater increases in hemoglobin and ferritin levels compared to iron polysaccharide complex, supporting its use as first-line therapy 5
• While one study in infants showed better ferritin increases with ferrous bisglycinate 6, this finding hasn't been consistently demonstrated in adult populations with severe iron deficiency anemia 3

Algorithm for Iron Therapy in Severe Iron Deficiency Anemia

1. Start with ferrous sulfate 200 mg once daily (65 mg elemental iron)
2. Take on an empty stomach with 80-500 mg vitamin C
3. Monitor hemoglobin after 2 weeks - should increase by at least 1 g/dL
4. If inadequate response or intolerance:
   • Try alternate-day dosing of ferrous sulfate
   • If still ineffective, switch to IV iron
5. Continue treatment for 3 months after normalization of hemoglobin
6. Monitor hemoglobin and iron indices every 3 months for the first year