From the Guidelines
Intravenous (IV) iron formulations, specifically ferric carboxymaltose, increase serum ferritin levels the fastest compared to oral iron supplements. When administered intravenously, iron bypasses the intestinal absorption process, allowing for direct delivery into the bloodstream and rapid incorporation into ferritin stores. According to the most recent and highest quality study 1, IV iron is indicated if a patient cannot tolerate oral iron or if blood counts or iron stores do not improve with oral iron supplementation. Common IV iron preparations include iron sucrose (Venofer), ferric carboxymaltose (Injectafer), and iron dextran (INFeD), typically administered in doses of 200-1000mg per session depending on the specific formulation and patient needs.
Some key points to consider when using IV iron include:
- Treatment protocols usually involve 1-5 infusions over several weeks, with significant ferritin increases often seen within 1-2 weeks after administration 1
- IV iron is particularly beneficial for patients with severe iron deficiency, malabsorption disorders, inflammatory bowel disease, or those who cannot tolerate oral supplements 1
- The rapid increase in ferritin occurs because IV iron directly enters the reticuloendothelial system where it's processed and stored as ferritin, bypassing the rate-limiting step of intestinal absorption that slows oral supplementation 1
- However, IV administration requires healthcare supervision and carries risks of infusion reactions, so it's typically reserved for cases where oral supplementation is insufficient or inappropriate 1
In terms of specific patient populations, the European Crohn's and Colitis Organization (ECCO) guidelines recommend IV iron as first-line treatment in patients with clinically active IBD, with previous intolerance to oral iron, with haemoglobin below 100 g/L, and in patients who need erythropoiesis-stimulating agents 1. Additionally, IV iron has been shown to be more effective and better tolerated than oral iron in patients with IBD, with a faster response and lower rates of gastrointestinal adverse events 1.
From the FDA Drug Label
Increases from baseline in mean ferritin (264.2 ± 224.2 ng/mL in Cohort 1 and 218.2 ± 211. 4 ng/mL in Cohort 2), and transferrin saturation (13 ± 16% in Cohort 1 and 20 ± 15% in Cohort 2) were observed at Day 35 in Injectafer-treated patients Increases from baseline in mean ferritin (734.7 ± 337.8 ng/mL) and transferrin saturation (30 ± 17%) were observed prior to Day 56 in Injectafer-treated patients. In Injectafer-treated patients, change from Baseline to Week 24 in serum ferritin was 269 ng/mL (229,309)
The type of iron that increases ferritin (serum) the fastest is Intravenous Ferric Carboxymaltose (FCM), also known as Injectafer.
- Key points:
- Ferric Carboxymaltose increased ferritin levels by 264.2 ng/mL and 218.2 ng/mL in Cohort 1 and Cohort 2, respectively, at Day 35.
- Ferric Carboxymaltose increased ferritin levels by 734.7 ng/mL prior to Day 56.
- Ferric Carboxymaltose increased ferritin levels by 269 ng/mL at Week 24. 2
From the Research
Types of Iron and Their Effects on Ferritin Levels
- Ferric carboxymaltose: Studies have shown that intravenous administration of ferric carboxymaltose rapidly improves haemoglobin levels and replenishes depleted iron stores in patients with iron-deficiency anaemia 3, 4. It has been found to increase serum ferritin levels and transferrin saturation, with improvements in haemoglobin levels being more rapid with ferric carboxymaltose than with ferrous sulfate.
- Ferrous sulfate: This is a commonly used oral iron supplement, and studies have compared its efficacy with ferric carboxymaltose and other iron formulations 5, 6, 7. While it is effective in increasing haemoglobin levels and restoring iron stores, its effects on ferritin levels may be slower compared to intravenous iron formulations like ferric carboxymaltose.
- Ferric citrate: This oral medication has been shown to be effective in treating iron deficiency anaemia in patients with chronic kidney disease, with a greater increase in transferrin saturation and ferritin levels compared to ferrous sulfate 6.
- Iron bis-glycinate chelate: A study found that supplementation with iron bis-glycinate chelate resulted in higher ferritin concentration 6 months after supplementation compared to ferrous sulfate 7.
Comparison of Iron Formulations
- Intravenous iron formulations like ferric carboxymaltose may have a faster effect on increasing ferritin levels compared to oral iron supplements like ferrous sulfate 3, 4.
- Oral iron formulations like ferric citrate and iron bis-glycinate chelate may have a slower but still significant effect on increasing ferritin levels 6, 7.
- The choice of iron formulation may depend on the individual's specific needs and medical condition, as well as the severity of iron deficiency anaemia.