An iron infusion is a medical procedure that delivers iron directly into the bloodstream, typically through a vein in the arm or hand. It’s often recommended when oral iron supplements are ineffective, poorly tolerated, or when a rapid increase in iron levels is needed. The primary goal is to replenish the body’s iron stores, essential for producing hemoglobin, the protein in red blood cells that carries oxygen throughout the body. This intravenous approach allows for faster, more efficient iron delivery than oral supplementation.
The Active Ingredient: Iron Compounds
The active ingredients in iron infusions are not “raw” iron, but specially formulated compounds designed for safe, effective delivery. These are typically iron-carbohydrate nanoparticles, with an iron-oxyhydroxide core encased in a carbohydrate shell. This complex structure stabilizes the iron and controls its release, minimizing toxicity from free iron in the bloodstream.
One common type is iron dextran, a complex of ferric hydroxide and dextran, designed for slow, controlled release. It can be administered intravenously or intramuscularly. Another widely used compound is iron sucrose, a complex of iron(III) hydroxide and sucrose. Iron sucrose has a lower potential for allergic reactions than older iron dextran formulations and is often used for patients with chronic kidney disease.
Ferric carboxymaltose is a newer, dextran-free intravenous formulation, with a ferric hydroxide core stabilized by a carbohydrate shell. It allows for large iron doses in shorter infusion times and typically doesn’t require a test dose. Ferumoxytol is an advanced intravenous preparation of superparamagnetic iron oxide nanoparticles coated with a semi-synthetic carbohydrate shell. This design facilitates rapid uptake by specific cells while minimizing free iron toxicity. Iron isomaltoside 1000, also known as ferric derisomaltose, is a highly stable iron-carbohydrate complex that can deliver large iron doses.
The Delivery Vehicle and Other Components
Beyond the active iron compound, iron infusion solutions contain other components for safe, effective delivery into the bloodstream. The iron compound is dissolved or suspended within a liquid base, typically sterile saline solution (sodium chloride 0.9%). This solution is isotonic, meaning it has a similar salt concentration to the body’s fluids, important for safe intravenous administration.
The saline solution prevents cells from shrinking or swelling, maintaining cellular integrity. Sterile water for injection may also be used as a solvent in some formulations. These carrier solutions allow iron particles to be evenly dispersed and delivered smoothly into the circulatory system, also diluting concentrated iron compounds for direct intravenous infusion.
While the iron compound and saline solution are primary constituents, some formulations may include minor excipients or stabilizers. These components help maintain the integrity and stability of the iron compound within the solution. They can prevent aggregation of iron nanoparticles or extend product shelf life.
How the Body Processes Infused Iron
Iron infusions are designed to interact effectively with the body’s natural iron processing systems. The iron compounds, encapsulated within carbohydrate shells, are formulated to be stable in the bloodstream. This stability prevents premature release of free iron, which can be toxic in high concentrations. The carbohydrate coating ensures controlled iron release as the complex is processed by the body.
Upon intravenous administration, these iron-carbohydrate complexes are primarily taken up by cells of the reticuloendothelial system (RES), especially macrophages in the liver, spleen, and bone marrow. Inside these macrophages, the carbohydrate shell of the iron complex degrades, and iron is released.
Once released from the complex within macrophages, iron follows several pathways. Some iron is stored in cells as ferritin, an iron storage molecule. The remaining iron is exported into the bloodstream, binding to transferrin. Transferrin transports iron throughout the body to cells requiring it, such as those in the bone marrow for hemoglobin production.