What are the maximum single‑dose limits and maximum weekly dosing frequencies for intravenous iron preparations (iron sucrose [Venofer], ferric gluconate [Ferrlecit], low‑molecular‑weight iron dextran [INFeD/Dexferrum], ferric carboxymaltose [Ferinject/Injectafer], ferumoxytol [Feraheme])?

Maximum Dose and Frequency of Intravenous Iron

The maximum single dose and weekly frequency of IV iron depends on the specific formulation: ferric carboxymaltose and ferumoxytol allow up to 1000 mg per week, iron sucrose permits 200-500 mg per dose (typically 200 mg), ferric gluconate is limited to 125 mg per dose, and low-molecular-weight iron dextran can be given as a total dose infusion but requires 4-6 hours. 1, 2, 3

Ferric Carboxymaltose (Ferinject/Injectafer)

This is the most practical formulation for rapid iron repletion in most clinical scenarios.

Maximum Dosing Parameters

• Maximum single dose: 1000 mg iron per administration 1, 4
• Maximum weekly dose: 1000 mg iron per week 5, 1
• Administration time: 15-30 minutes (can be given as undiluted IV push over 15 minutes or diluted in 100-250 mL normal saline) 1, 4

Practical Dosing Algorithm

For patients requiring >1000 mg total iron deficit:

• Administer doses separated by at least 7 days 1
• Typical regimen: 1000 mg Day 1, then 500-1000 mg at Week 1 (depending on body weight and hemoglobin) 1

Critical Safety Thresholds

• Do not administer if hemoglobin >15 g/dL 1
• Mandatory 30-minute post-infusion observation for hypersensitivity reactions 1
• Avoid in active bacteremia – discontinue treatment if infection develops 1

Important Monitoring Caveat

• Do not recheck iron parameters within 4 weeks of administration, as ferritin will be falsely elevated 1
• Reassess iron status at 3 months after initial treatment 1
• Monitor serum phosphate in patients requiring repeat courses within 3 months, as hypophosphatemia occurs in 47-75% of such cases 1, 6

Iron Sucrose (Venofer)

This formulation requires multiple visits but has an excellent safety profile with no test dose required.

Maximum Dosing Parameters

• Maximum single dose: 200 mg per administration (some guidelines allow up to 500 mg over 3.5 hours in IBD patients, but 200 mg is standard) 5, 2
• Administration time: 10 minutes as IV push (undiluted) for 200 mg doses 2
• Frequency: Can be given 2-3 times weekly in hemodialysis patients 2

Practical Considerations

• No test dose required (unlike iron dextran) 2
• Requires 5-10 infusions to deliver 1000-2000 mg total iron deficit 5
• Most practical for hemodialysis patients where it can be administered directly into the dialysis line 2

Monitoring Intervals

• Allow at least 7 days before rechecking iron parameters after 200 mg doses 2
• Monitor iron studies every 3 months during maintenance therapy 2

Ferric Gluconate (Ferrlecit)

This is the most limited formulation but remains cost-effective for hemodialysis patients.

Maximum Dosing Parameters

• Maximum single dose: 125 mg per infusion 3
• Administration time: 60 minutes (infused in 50-100 mL saline) 3
• Standard regimen: 125 mg weekly for 8 consecutive weeks (total 1000 mg) 3

Key Advantages

• No test dose required (unlike iron dextran) 3
• Lowest cost: approximately $610 for 1000 mg total dose vs. $3,470 for ferric carboxymaltose 3
• No reported fatalities in clinical use 3

When to Choose Ferric Gluconate

• Hemodialysis patients with routine dialysis access 3
• Patients with cost constraints 3
• Patients who have had reactions to iron dextran 3

When to Avoid

• Patients requiring rapid iron repletion (requires 8 weekly visits) 3
• Patients who cannot return for multiple infusions 3

Low-Molecular-Weight Iron Dextran (INFeD/Dexferrum)

This formulation allows total dose infusion but requires prolonged administration time.

Maximum Dosing Parameters

• Can administer total calculated iron deficit in single infusion 7, 8
• Administration time: 4-6 hours for total dose infusion 5, 7
• Test dose: May be advisable but no longer mandatory 5

Safety Considerations

• Higher risk of anaphylaxis compared to newer formulations due to larger carbohydrate shell 5
• Requires prolonged monitoring during extended infusion 7

Ferumoxytol (Feraheme)

This formulation allows rapid high-dose administration but has specific safety concerns.

Maximum Dosing Parameters

• Standard dosing: 510 mg per dose, given as two doses separated by 3-8 days 7
• Administration time: Can be given rapidly 7
• Total course: 1020 mg over 1-2 weeks 7

Important Safety Note

• Higher risk of anaphylaxis due to larger carbohydrate shell (similar to iron dextran) 5
• Requires appropriate emergency preparedness 7

Iron Isomaltoside 1000

This formulation is available in Europe and allows high single doses.

Maximum Dosing Parameters

• Maximum single dose: 20 mg/kg body weight (up to 1000 mg) 5
• Minimum infusion time: 15 minutes for doses up to 1000 mg; >30 minutes if dose exceeds 1000 mg 5

Common Pitfalls to Avoid Across All Formulations

1. Premature iron studies: Do not measure ferritin or TSAT within 4 weeks of IV iron administration – values will be falsely elevated and mask inadequate repletion 1, 3

2. Underdosing with single infusions: A single 1000 mg ferric carboxymaltose infusion frequently fails to achieve complete iron repletion; most patients require 1500-2000 mg total 1

3. Concurrent oral iron: Do not use oral iron simultaneously with IV iron – it increases side effects without additional benefit 3

4. Ignoring infection: Withhold IV iron in patients with active bacteremia or ongoing infection 1, 2

5. Exceeding hemoglobin threshold: Do not administer any IV iron formulation when hemoglobin >15 g/dL 1

6. Inadequate observation: All IV iron formulations require at least 30 minutes of post-infusion monitoring in a facility equipped to manage hypersensitivity reactions 1, 3

Algorithm for Formulation Selection

Choose ferric carboxymaltose or ferumoxytol when:

• Rapid iron repletion needed (1-2 visits) 1, 7
• Patient cannot return for multiple visits 1
• Total iron deficit >1000 mg 1

Choose iron sucrose when:

• Patient is on hemodialysis with routine access 2
• Gradual repletion is acceptable 2
• Intermediate cost consideration 2

Choose ferric gluconate when:

• Patient is on hemodialysis 3
• Cost is primary concern 3
• Patient had prior reaction to iron dextran 3

Avoid iron dextran unless:

• Total dose infusion is specifically required 7
• Patient can tolerate 4-6 hour infusion 5
• Other formulations are unavailable 7