What is the appropriate iron dextran (INFeD) dosing for a 70‑kg adult with hemoglobin 7 g/dL who needs to be increased to 12 g/dL?

INFeD Dosing for Hemoglobin 7 g/dL

For a 70-kg adult with hemoglobin 7 g/dL requiring correction to 12 g/dL, administer a calculated total dose of INFeD (low molecular weight iron dextran) based on the FDA-approved formula, which typically yields approximately 1,500–2,000 mg of elemental iron for this degree of anemia. 1

Dose Calculation Using FDA Formula

The FDA-approved INFeD dosing formula for adults over 15 kg is:

Dose (mL) = 0.0442 × (Desired Hb – Observed Hb) × LBW + (0.26 × LBW) 1

For your 70-kg patient:

• Desired Hb = 12 g/dL (or 14.8 g/dL if targeting normal adult levels)
• Observed Hb = 7 g/dL
• LBW (Lean Body Weight) = 70 kg (use actual weight if less than calculated lean body weight) 1

Using target Hb of 12 g/dL:

• Dose (mL) = 0.0442 × (12 – 7) × 70 + (0.26 × 70)
• Dose (mL) = 0.0442 × 5 × 70 + 18.2
• Dose (mL) = 15.47 + 18.2 = 33.67 mL
• Total elemental iron = 33.67 mL × 50 mg/mL = 1,683 mg 1

Using target Hb of 14.8 g/dL (normal adult):

• Total dose would be approximately 2,100 mg elemental iron 1

Administration Protocol

Mandatory Test Dose

Administer a 0.5 mL (25 mg) IV test dose over at least 30 seconds, then observe for a minimum of 1 hour before proceeding with therapeutic dosing. 1 This is critical because anaphylactoid reactions, though rare, are serious and unpredictable with iron dextran. 2

Therapeutic Dose Administration Options

Option 1: Daily Divided Doses (Safer, FDA-Recommended)

• Maximum 2 mL (100 mg) per day until total calculated dose is reached 1
• Administer undiluted at ≤50 mg (1 mL) per minute 1
• This approach requires 17–21 visits for a total dose of 1,683–2,100 mg

Option 2: Total Dose Infusion (More Convenient, Off-Label)

• 1,000 mg diluted in 500 mL normal saline infused over 6 hours has been shown safe and effective in multiple studies 3, 4
• For doses >1,000 mg, guidelines suggest infusion times of 240–360 minutes 5
• This approach requires 2 visits (1,000 mg × 2) to deliver 2,000 mg total
• Research demonstrates this is effective with minimal adverse events when proper monitoring is in place 3, 6, 4

Critical Safety Considerations

Resuscitation preparedness is mandatory:

• Have epinephrine, diphenhydramine, corticosteroids, and resuscitation equipment immediately available 1
• Monitor vital signs during and for at least 30 minutes after infusion 7
• Keep patient under observation for at least 1 hour post-infusion 1

Contraindications:

• Active bacteremia is an absolute contraindication 8
• Defer treatment during active infection 8

Higher-risk patients requiring extra caution:

• History of multiple drug allergies 9
• Collagen vascular diseases (higher delayed reaction rates) 2
• Female gender (slightly increased adverse event risk) 9

Expected Outcomes and Monitoring

Hemoglobin response:

• Expect 1–2 g/dL increase within 4–8 weeks after completing iron repletion 7
• IV iron produces faster hemoglobin recovery than oral iron when Hb <9 g/dL 2

Iron parameter targets:

• Transferrin saturation >20% 7
• Ferritin >100 ng/mL 7

Recheck laboratory studies 4–8 weeks after the last dose to assess response and avoid checking too early, which yields inaccurate results 7

Product-Specific Advantage of INFeD

INFeD (low molecular weight iron dextran) allows total dose infusion up to the full calculated deficit in a single session, unlike iron sucrose (maximum 200 mg per dose) or ferric gluconate (maximum 125 mg per dose). 5, 8 This makes INFeD the most practical option for severe anemia requiring >1,500 mg elemental iron, despite requiring longer infusion times and more intensive monitoring than newer formulations. 8

Low molecular weight iron dextran (INFeD) has a significantly lower adverse event profile than high molecular weight iron dextran (Dexferrum), with fewer anaphylactoid reactions. 8, 9 Studies show adverse event rates of 2.1% for low molecular weight versus 5.6% for high molecular weight formulations. 9

Common Pitfalls to Avoid

• Do not skip the test dose—anaphylactoid reactions are unpredictable and can be life-threatening 1, 2
• Do not infuse faster than 50 mg/minute for daily dosing 1
• Do not administer during active infection or bacteremia 8
• Do not check iron studies <2 weeks after large doses (≥1,000 mg) as results will be falsely elevated 7
• Do not use the anemia correction formula for blood loss replacement—that requires a different calculation 1