What is the role of iron dextran in treating iron deficiency anemia?

Iron Dextran for Iron Deficiency Anemia

Iron dextran is an effective intravenous iron formulation reserved for patients who cannot tolerate or have failed oral iron therapy, with low molecular weight iron dextran (INFeD) being the preferred formulation due to lower anaphylaxis risk compared to high molecular weight preparations. 1

Indications for Iron Dextran

Use iron dextran when:

• Patients have absolute iron deficiency (ferritin <30 ng/mL, transferrin saturation <15%) and cannot tolerate oral iron 1, 2
• Oral iron therapy has failed to achieve adequate hematologic response after 4-6 weeks 1
• Gastrointestinal side effects from oral iron are intolerable 3
• Rapid iron repletion is needed (e.g., ongoing blood loss exceeding oral replacement capacity) 1, 2
• Malabsorption conditions prevent adequate oral iron absorption 1, 2
• Patients with chronic kidney disease on erythropoietin therapy require iron supplementation 1

Formulation Selection

Always use low molecular weight iron dextran (INFeD) rather than high molecular weight formulations (Dexferrum, now off market). 1 The low molecular weight preparation has significantly lower rates of serious adverse reactions while maintaining equivalent efficacy. 1

Administration Protocol

Total Dose Infusion (TDI) Method:

• Calculate total iron deficit using standard formulas 4
• Administer mandatory 25 mg test dose over 30 minutes to assess for anaphylactic reactions 1, 2
• If test dose is tolerated, infuse remaining dose (up to 1000 mg maximum) diluted in normal saline over 1-6 hours 1, 2
• Infusion rate should not exceed 100 mg/minute 5

Divided Dose Method (Alternative):

• Administer 100-125 mg IV weekly for 8-10 doses in hemodialysis patients 1
• For cancer patients, give 125 mg IV over 60 minutes weekly for up to 8 doses (maximum 1000 mg total) 2

Safety Considerations and Monitoring

Contraindications:

• Active infection (withhold iron dextran until infection resolves) 1, 2
• Known hypersensitivity to iron dextran products 4

Common adverse effects (occur in 1-2% of patients): 2

• Nausea (2.2%), headache, vomiting, chills, backache (each ~1%) 6
• Hypotension, hypertension, pain, dyspnea, pruritus, dizziness 1

Serious reactions:

• Anaphylactoid reactions occur in <1:250,000 administrations with modern formulations 1
• Life-threatening reactions are unpredictable but rare with low molecular weight preparations 5
• Delayed reactions (arthralgia, myalgia) more common in women and collagen-vascular diseases 5, 3

Monitoring parameters:

• Observe patient during and for 30-60 minutes after infusion for immediate reactions 2
• Recheck iron studies (ferritin, transferrin saturation, hemoglobin) 3-4 weeks after final dose 2
• Do not recheck iron parameters within 2 weeks of doses ≥1000 mg, as ferritin will be falsely elevated 1

Expected Response

Hematologic improvement:

• Reticulocytosis occurs within days in most patients 7
• Mean hemoglobin increase of 2.0 g/dL and hematocrit increase of 5.3% within 5-9 weeks 6, 7
• Faster response than oral iron when hemoglobin <9 g/dL 5
• Complete resolution of iron deficiency in 40-54% of patients with normal renal function 3

Alternative IV Iron Products

If contraindications to iron dextran exist, consider: 1, 2

• Ferric gluconate: 125 mg IV over 60 minutes weekly (maximum individual dose 125 mg) - no test dose required 1
• Iron sucrose: 200 mg IV over 30 minutes every 2-3 weeks (maximum individual dose 200-500 mg) - no test dose required 1
• Ferric carboxymaltose: 750-1000 mg IV over 15 minutes (can give up to 20 mg/kg) - no test dose required 1

These newer formulations have lower anaphylaxis risk but cannot be given as total dose infusions >1000 mg in a single session like iron dextran. 1, 2

Key Clinical Pitfalls

• Never use high molecular weight iron dextran - it has unacceptably high adverse reaction rates 1
• Do not skip the test dose - anaphylaxis is unpredictable and can be life-threatening 1, 2
• Avoid iron supplementation when ferritin >800 ng/mL or transferrin saturation >50% - no additional benefit and potential toxicity 1
• Do not administer during active infection - theoretical risk of promoting bacterial growth 1, 2
• Wait appropriate intervals before rechecking iron studies - premature testing yields falsely elevated ferritin 1