Iron is absorbed from the gastrointestinal (GI) tract from
food and stored in the liver in the form of ferritin. When needed by the body,
the ferritin is released into the bone marrow to help make new red blood cells.
When the red blood cells reach the end of their life cycle and undergo
hemolysis, iron from those cells can be recycled and reused. If iron stores
become depleted, either due to loss of blood, lack of adequate iron intake in
the diet, or the lack of the body to absorb iron from the GI tract, iron-deficiency
anemia (IDA) can occur. This can result in inadequate provision of oxygen to
the body tissues and organs leading to multiple health issues. Although there
can be other causes of anemia, IDA is the most common cause worldwide. The
estimated prevalence of IDA in North America is 2.9%.
Common causes of IDA can include menstruation, pregnancy,
breastfeeding, chronic kidney disease (CKD), major surgery, physical trauma, GI
diseases (ulcerative colitis, Crohn disease, celiac disease, peptic ulcer
disease), GI malignancies, bariatric procedures, and vegetarian or vegan diets.
There are multiple other less common causes of IDA as well. Efforts to identify
and treat the cause(s) are necessary.
Blood tests are used to diagnose IDA. Results of laboratory
tests will demonstrate the following: low hemoglobin (hgb), low mean cellular
volume (MCV), low serum iron, low ferritin, low iron saturation, high
transferrin, and high total iron-binding capacity (TIBC). When an individual is
found to be anemic, as demonstrated by a low hgb, the next step is to look at
the ferritin levels. There are different recommendations for the cut-off value
for serum ferritin levels to define IDA proposed by different professional
societies. The World Health Organization (WHO) recommends less than 12 ng/mL for
healthy individuals under the age of 5 years, and less than 15 ng/mL for healthy
individuals ages 5 years and above. For individuals with infection or
inflammation, the levels increase to less than 30 ng/mL and less than 70 ng/mL for the same
groups. The National Heart, Lung, and Blood Institute (NHLBI) recommend a
cut-off level for ferritin at less than 10 ng/mL. The American Gastroenterological
Association (AGA) recommends a cut-off level for ferritin at less than 45 ng/mL.
Once IDA has been identified, treatment can begin.
Identifying the cause of the IDA can occur at the same time that the IDA is
being treated. Treatment is usually begun with oral iron supplementation. If
the individual is unable to tolerate oral iron supplementation, has a
documented contraindication to oral iron supplementation, or has a documented
nonresponse to oral iron supplementation, then erythropoiesis-stimulating
agents (ESAs) and/or intravenous (IV) iron can be ordered. ESAs work by helping
the bone marrow make more red blood cells (RBCs). Individuals who are on
hemodialysis for end-stage renal disease (ESRD) can receive these medications
while they are undergoing their dialysis treatments. If the anemia is severe
enough that the individual has symptoms (e.g., fatigue, weakness, dizziness,
lightheadedness), then the individual may require transfusions of blood
products.
Ferric carboxymaltose (Injectafer) is a colloidal iron (III) hydroxide in complex with
carboxymaltose, a carbohydrate polymer that releases iron.
Ferric
derisomaltose (Monoferric) is a complex of iron (III) hydroxide and
derisomaltose, an iron carbohydrate oligosaccharide that releases iron. Iron
binds to transferrin for transport to erythroid precursor cells to be
incorporated into hemoglobin.
Ferumoxytol (Feraheme) consists
of a superparamagnetic iron oxide that is coated with a carbohydrate shell,
which helps to isolate the bioactive iron from plasma components until the
iron-carbohydrate complex enters the
reticuloendothelial system macrophages of the liver, spleen, and bone marrow.
The iron is released from the iron-carbohydrate complex within vesicles in the
macrophages. Iron then either enters the intracellular storage iron pool (e.g.,
ferritin) or is transferred to plasma transferrin for transport to erythroid
precursor cells for incorporation into hemoglobin.
Iron dextran (INFeD) is a complex of ferric hydroxide and dextran that releases iron into the
circulation in order to replenish hemoglobin and depleted iron stores.
Iron sucrose (Venofer) is an aqueous complex of polynuclear iron (III) hydroxide in sucrose.
Following intravenous administration, iron sucrose (Venofer) is dissociated into iron and
sucrose and the iron is transported as a complex with transferrin to target
cells including erythroid precursor cells. The iron in the precursor cells is
incorporated into hemoglobin as the cells mature into red blood cells.
Sodium ferric
gluconate complex in sucrose (Ferrlecit) is a stable macromolecular complex and
is used to replete the body content of iron.
OFF-LABEL INDICATIONS
There may be additional indications contained in the Policy section of this
document due to evaluation of criteria highlighted in the Company's off-label
policy, and/or review of clinical guidelines issued by leading professional
organizations and government entities.