Calculating IV Iron Requirements
The recommended formula for calculating IV iron requirements is based on body weight and hemoglobin levels, with specific dosing tables available for different formulations like ferric carboxymaltose. 1, 2
Standard Formula for IV Iron Calculation
For most patients, IV iron requirements can be calculated using these approaches:
1. Ganzoni Formula (Traditional Method)
- Total iron deficit (mg) = Body weight (kg) × [Target Hb - Actual Hb (g/dL)] × 2.4 + Iron stores
- Where iron stores = 500 mg for adults >35 kg
2. Simplified Dosing Based on Weight and Hemoglobin
For ferric carboxymaltose (most commonly used):
| Hemoglobin g/dL | Body weight <70 kg | Body weight ≥70 kg |
|---|---|---|
| 10-12 (women) | 1000 mg | 1500 mg |
| 10-13 (men) | 1000 mg | 1500 mg |
| 7-10 | 1500 mg | 2000 mg |
| <7 | 1500 mg + additional 500 mg | 2000 mg + additional 500 mg |
3. For Heart Failure Patients
Specific dosing for patients with heart failure and iron deficiency:
| Weight <70 kg | Weight ≥70 kg |
|---|---|
| Hb <10 g/dL: 1000 mg on day 1,500 mg at week 6 | Hb <10 g/dL: 1000 mg on day 1,1000 mg at week 6 |
| Hb 10-14 g/dL: 1000 mg on day 1, no dose at week 6 | Hb 10-14 g/dL: 1000 mg on day 1,500 mg at week 6 |
| Hb >14 to <15 g/dL: 500 mg on day 1, no dose at week 6 | Hb >14 to <15 g/dL: 500 mg on day 1, no dose at week 6 |
Special Populations
Hemodialysis Patients
- Initial iron repletion: 25-100 mg IV iron dextran weekly for 10 weeks or 31.25-125 mg iron gluconate weekly for 8 weeks
- Maintenance: 250-1000 mg within 12 weeks, administered weekly or every other week 3
Pediatric Patients
Based on weight:
- <10 kg: 25 mg per dose (total course 125 mg)
- 10-20 kg: 50 mg per dose (total course 250 mg)
20 kg: 100 mg per dose (total course 500 mg) 3
Administration Considerations
Different IV iron formulations have varying maximum single doses and administration times:
| Preparation | Maximum Single Dose | Administration Time |
|---|---|---|
| Ferric Derisomaltose | 20 mg/kg (up to 1500 mg) | 15-30+ minutes |
| Ferric Carboxymaltose | 750 mg (US) | 15 minutes |
| Iron Sucrose | 200 mg | Multiple doses needed |
| Ferumoxytol | 510 mg | Multiple doses needed |
Monitoring Parameters
- Monitor hemoglobin every 4 weeks until normalization
- Re-evaluate iron status 8-12 weeks after completion of therapy
- Target parameters: Hb ≥11-12 g/dL, ferritin >100 ng/mL, TSAT >20% 1
- For repeat courses, check serum phosphate levels, especially if retreatment occurs within 3 months 2
Important Considerations
- IV iron is preferred over oral iron for both absolute iron deficiency anemia (AIDA) and functional iron deficiency anemia (FIDA) 1
- Avoid IV iron during active infection 1
- Do not administer IV iron on the same day as anthracycline chemotherapy 1
- Monitor patients for at least 30 minutes after infusion for hypersensitivity reactions 1
- Test doses are required for iron dextran but not for ferric gluconate or iron sucrose 3
By following these dosing guidelines and monitoring parameters, you can effectively calculate and administer IV iron to correct iron deficiency while minimizing potential adverse effects.