Iron Infusion Protocol and Laboratory Monitoring
Direct Answer
Iron parameters should be re-evaluated 3 months after intravenous iron infusion, with laboratory testing including CBC, ferritin, and transferrin saturation performed 4-8 weeks after the last dose. 1, 2
Administration Protocol
Dosing Regimens by Formulation
Ferric carboxymaltose (Ferinject):
- Maximum 1000 mg iron per week 1
- Administered as undiluted slow bolus injection at 100 mg/min (15 minutes for 1000 mg dose) 1
- Can also be infused in 250 mL normal saline over 15 minutes 1
- Observe patient for adverse effects for at least 30 minutes post-injection 1
Iron sucrose (Venofer):
- 200 mg iron over 10 minutes as bolus dosing 1
- Alternative: 200 mg in 50-100 mL saline over 30-60 minutes 1
- Maximum single dose: 200 mg 1
Ferric gluconate (Ferrlecit):
- Adult: 125 mg elemental iron per dialysis session 3
- Dilute in 100 mL 0.9% sodium chloride, infuse over 1 hour 3
- Alternative: undiluted slow IV injection at rate up to 12.5 mg/min 3
- Pediatric (≥6 years): 1.5 mg/kg (max 125 mg) diluted in 25 mL saline over 1 hour 3
Iron dextran (Cosmofer):
- Can administer 500-1000 mg in single dose diluted in 250 mL normal saline over 1 hour 1
- For hemodialysis patients: maximum 100 mg per dose to minimize arthralgias/myalgias 1
Laboratory Monitoring Schedule
Timing of Laboratory Tests
Do NOT test iron parameters within 4 weeks of IV iron administration - ferritin levels increase markedly and cannot be utilized as reliable markers during this period. 2
Optimal testing intervals:
- 4-8 weeks after last infusion: Check CBC and iron parameters (ferritin, TSAT) 2
- 3 months after iron replacement: Re-evaluate iron status for need of additional repletion 1, 2
- For doses ≥1000 mg: Wait minimum 2 weeks, though 4-8 weeks optimal 2
- For smaller doses (100-125 mg weekly): Can measure without interrupting therapy 2
Parameters to Monitor
Essential laboratory tests:
Expected response:
- Hemoglobin should increase 1-2 g/dL within 4-8 weeks 2
- Initial Hb rise more rapid with parenteral iron, but at 12 weeks similar to oral therapy 1
Long-Term Monitoring
After Achieving Target Hemoglobin
For patients on regular iron therapy:
- Monitor TSAT and ferritin at least every 3 months 2
- Once normal, monitor Hb and red cell indices every 3 months for 1 year, then annually 1
For chronic conditions:
- Evaluate iron status 1-2 times per year as routine follow-up 2
- In chronic kidney disease without erythropoietin: every 3-6 months 2
Thresholds for Withholding Iron
Stop or hold iron infusion if:
- TSAT exceeds 50% 1, 2
- Ferritin exceeds 800-1000 ng/mL 1, 2
- Evidence of iron overload 1
- Active bacteremia 1
Target levels (chronic kidney disease):
Special Considerations
MRI Timing After Infusion
Wait 1 month after Monofer (iron isomaltoside) before MRI to avoid magnetic interference. 2 This differs from other preparations: iron sucrose/ferric carboxymaltose (1 week), high-molecular-weight iron dextran (3 months), ferumoxytol (6 months). 2
Safety Monitoring
Resuscitation facilities must be available - anaphylaxis may occur with all IV iron preparations, though risk is <1:250,000 with modern formulations. 1
Monitor for hypotension during and after each dose, particularly with iron sucrose and ferric gluconate. 1, 3
When to Investigate Further
If no response or Hb decreases after treatment:
- Investigate for occult blood loss 2
- Consider other causes of anemia 1
- Re-evaluate if Hb/red cell indices cannot be maintained with supplementation 1
Common Pitfalls to Avoid
- Testing too early: Ferritin falsely elevated if checked before 4 weeks, leading to undertreatment 1, 2
- Exceeding maximum single doses: Doses >125 mg ferric gluconate associated with higher adverse event rates 3
- Mixing with other medications: Do not mix iron preparations with other drugs or add to parenteral nutrition 3
- Wrong diluent: Use only 0.9% sodium chloride; compatibility with other vehicles not established 3