How much does Ferumoxytol (intravenous iron formulation) raise ferritin levels?

Ferumoxytol's Effect on Ferritin Levels

Ferumoxytol administration typically increases ferritin levels by approximately 300-380 ng/mL following the standard two-dose regimen of 510 mg each, with the effect measured at 35 days post-administration. 1

Ferumoxytol Dosing and Administration

• Ferumoxytol is administered as two 510 mg intravenous doses for a total of 1020 mg, with doses typically given 3-8 days apart 2
• Current FDA-approved administration requires infusion over at least 15 minutes per dose, rather than the original rapid injection method which caused higher rates of infusion reactions 2
• Single total dose infusion of 1020 mg over 30 minutes has been shown to be safe and effective in recent studies, though this remains off-label 3

Effect on Ferritin Levels

• FDA data shows ferumoxytol increases ferritin by approximately 300.7 ± 214.9 ng/mL in non-dialysis CKD patients and 381.7 ± 278.6 ng/mL in another non-dialysis CKD cohort at 35 days post-administration 1
• In hemodialysis patients, ferumoxytol increases ferritin by approximately 233.9 ± 207.0 ng/mL at 35 days 1
• The increase in ferritin is substantially greater than that seen with oral iron therapy, which shows minimal change in ferritin levels (0.3 ± 82.0 ng/mL to 6.9 ± 60.1 ng/mL) 1

Factors Affecting Ferritin Response

• Baseline ferritin levels affect the magnitude of increase, with studies showing varying responses depending on initial iron status 2
• Patients with higher baseline ferritin (>500 ng/mL) may still benefit from IV iron therapy if they have low transferrin saturation, though the magnitude of ferritin increase may differ 2
• The presence of inflammation can affect ferritin levels independently of iron stores, potentially complicating interpretation of post-treatment ferritin levels 4

Clinical Considerations

• Ferritin increases from ferumoxytol are accompanied by improvements in hemoglobin (approximately 0.8-1.2 g/dL increase) and transferrin saturation (approximately 6-10% increase) at 35 days 1, 5
• The pharmacokinetics of ferumoxytol follow a two-compartment model with Michaelis-Menten elimination, which affects the rate and extent of ferritin elevation 6
• Single-dose administration (1020 mg) appears to produce similar efficacy outcomes to the standard two-dose regimen, though the specific impact on ferritin levels may differ 3, 7

Monitoring Recommendations

• Ferritin levels should be measured approximately 4-5 weeks after administration to assess response 1
• Caution is advised when interpreting ferritin levels in patients with concurrent inflammatory conditions, as ferritin is an acute phase reactant 4
• For patients requiring additional iron therapy, reassessment of iron parameters including ferritin is recommended before administering subsequent doses 1

Safety Considerations

• Very high ferritin levels (>800 ng/mL) may raise safety concerns for additional IV iron administration, though specific thresholds for withholding therapy remain debated 4
• The National Kidney Foundation suggests that IV iron may still be beneficial in selected patients with elevated ferritin but low transferrin saturation, particularly in chronic kidney disease 4