Ferumoxytol

Feraheme (ferumoxytol) is comprised of a superparamagnetic iron oxide that is coated with a carbohydrate shell, aiding in the isolation the bioactive iron from plasma components until the iron-carbohydrate complex enters the reticuloendothelial system macrophages of the liver, spleen and the bone marrow.

The iron is then released from the iron-carbohydrate complex within vesicles located in the macrophages. Iron then either enters the intracellular storage of iron (e.g., ferritin) or can be transferred to plasma transferrin for its transport to erythroid precursor cells for incorporation into hemoglobin.

A therapeutic response to iron therapy depends upon the individual's iron stores and ability to utilize the iron. The systemic use of iron is influenced by the cause of the deficiency in addition to the illnesses/conditions that may affect erythropoiesis. Iron therapy by itself does not increase red blood cell (RBC) production. Administration of iron improves only the anemia associated with iron deficiency.

Iron-containing proteins and enzymes are essential in oxidation-reduction reactions, particularly those in the mitochondria. Iron is a part of myoglobin and various heme-enzymes, including the cytochromes, catalase, and peroxidase. Iron is an important component of the metalloflavoprotein _enzymes as well as the mitochondrial enzyme _alpha-glycerophosphate oxidase. In addition, iron serves as a cofactor for enzymes such as aconitase _and tryptophan _pyrrolase. Iron deficiency leads anemia and decreased oxygen delivery, but also reduces muscle metabolism and decreases mitochondrial activity.

Iron deficiency may also lead to defects in both learning and body thermoregulation. Therefore, iron is imperative to several metabolic functions in addition to erythropoiesis.

After intravenous administration, ferumoxytol replaces iron stores with less frequent side effects compared to the use of oral iron therapy. In addition, this agent generates T1 relaxation, producing a magnetic field and enhancing T2 relaxation, thereby darkening contrast media-containing structures in magnetic resonance imaging (MRI). Due to small particle size, ferumoxytol remains in the intravascular space for a prolonged period and so may be used as a blood pool agent.

T1 and T2, in radiology, refer to the timing of radiofrequency pulse sequences used to make images. The timing used to create T1 images results in images which emphasize fat tissue. The timing of radiofrequency pulse sequences utilized to create T2 images results in images which emphasize fat AND water within the body.