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Treatment of iron deficiency anemia

By: Maryam Sekhery, PharmD Candidate c/o 2020

           According to the World Health Organization, anemia is defined as having a level of Hemoglobin (Hb) below 13.0 g/dL in male adults, below 12.0 g/dL in female adults who are not pregnant, and below 11.0 g/dL in pregnant women.1 Hemoglobin is an iron-containing oxygen-transport metalloprotein in red blood cells which carries oxygen throughout the body.2 Hemoglobin levels differ with age and race, so one must carefully interpret borderline values. Approximately one-fourth of the world’s population has anemia and the predominant cause is iron deficiency. Patients with anemia often present with chronic fatigue, impaired cognitive function, and diminished well-being. When the cause of patients’ Iron Deficiency Anemia (IDA) is unknown, they are referred to a gastroenterologist because, in most cases, IDA has a gastrointestinal origin.1    

Patients who have IDA should be treated promptly. There is supporting evidence that in doing so, quality of life and physical condition, including symptoms of fatigue and cognitive deficits, are improved. Patients may also present with iron deficiency without anemia, which is associated with restless leg syndrome (RLS) and chronic fatigue. These symptoms improve when iron deficiency is corrected. Given the different clinical presentations of iron deficiency, each patient should be assessed individually when deciding on a treatment regimen.

IDA can be treated orally and/or intravenously. Oral iron absorption is limited – the maximum absorption of 100 mg of oral iron is only 20-25 percent of the administered dose, which is achieved in patients who are in the later stages of iron deficiency.1 As a result of its limited intestinal absorption, oral iron repletion occurs more slowly than intravenous iron repletion which limits its use in patients who require immediate repletion of iron stores. Oral iron also has dose-dependent gastrointestinal side effects including nausea, vomiting, abdominal pain and constipation. These side effects may cause nonadherence and result in a patient’s iron deficiency remaining uncorrected. Oral iron uptake may also be impaired in the presence of certain chronic diseases such as celiac disease, anemia of chronic disease (ACD), and autoimmune gastritis. In addition, there may be an increased risk of mucosal injury if the patient has been diagnosed with inflammatory bowel disease (IBD). The benefits of oral iron include its increased market availability, inexpensive cost, and convenience with respect to administration. The advantages and disadvantages of oral iron indicate that it can only be used in a limited subset of IDA patients who have minimal co-morbidities.

Intravenous iron therapy is another viable option for the treatment of IDA. It results in fast repletion of iron stores and is effective even when intestinal absorption is impaired. Most formulations are safe, but iron dextran should be avoided if possible – it has a black box warning for anaphylaxis.3 Intravenous iron lacks the convenience of oral formulations as it requires administration by a healthcare professional, resulting in a higher likeliness of patient discomfort as well as increased direct medical costs. Adverse effects of intravenous iron include its potential for iron overload and transient increases in oxidative stress. Given its ability to rapidly replete iron stores and minimization of gastrointestinal adverse effects, intravenous iron therapy should be considered in patients with iron deficiency anemia when oral therapy is ineffective or contraindicated. It is also a more feasible option for patients who have a history of nonadherence with oral medications.

Patients with IDA should be monitored throughout their course of iron therapy. When on oral iron, Hb levels are expected to increase by 2g/dL within 4-8 weeks, although some patients may show signs of improvement within a few days of starting therapy. If a patient does not appropriately respond to therapy within 4-8 weeks, the treatment regimen should be modified and transitioned to intravenous iron therapy. The cause of their lack of response to oral iron therapy should also be evaluated. Normalization of Hb levels can take up to three months and replacing iron stores (ferritin > 100 µg/L) may take even longer depending on the severity of IDA and the underlying etiology.1

One of the last line options for treatment of IDA is a blood transfusion. If a patient’s IDA is treated and managed properly, quality of life is improved, symptoms of iron deficiency are alleviated, and the need for a blood transfusion is reduced. Blood transfusions should only be considered in patients with chronic iron deficiency anemia. These patients usually present with active bleeding, hemodynamic instability, and/or critical anemia (Hb level <7g/dL). If all other treatments fail to correct the anemia, a blood transfusion may be necessary.1 Unfortunately, blood transfusions are a temporary solution and every attempt should be made to identify the underlying cause of a patient’s anemia so it can be properly managed.

Correction of iron deficiency is the optimal way to mitigate a patient’s IDA, which should be treated promptly upon diagnosis, as it is associated with a decreased quality of life and clinical outcomes in addition to increased healthcare costs. Patients who present with iron deficiency without anemia should be treated if they begin to experience symptoms of IDA, including fatigue, weakness, shortness of breath, fast heartbeat and chest pain.2 Given the advantages and disadvantages of the different iron therapies that are available, healthcare providers can choose the correct therapeutic regimen based on urgency, underlying conditions, and what is most convenient for their patient. A pharmacist’s role in the treatment of IDA may include identifying signs and symptoms, recommending agents to replete iron stores, managing side effects of oral iron, counseling patients on medication adherence, separating oral iron from interacting medications, and collaborating with providers to rule out underlying causes.

SOURCES:

  1. Jimenez, Kristine, et al. “Management of Iron Deficiency Anemia.” Gastroenterology & Hepatology, Millennium Medical Publishing, 04/2015, Retrieved 05/18/2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4836595/.
  2. “Low Hemoglobin Count.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 04/07/2018, Retrieved 05/18/2019, from https://www.mayoclinic.org/symptoms/low-hemoglobin/basics/definition/sym-20050760.
  3. Allergan Pharmaceuticals (2018, November). INFeD® (IRON DEXTRAN INJECTION USP) Rx only. Retrieved 05/18/2019, from https://www.allergan.com/assets/pdf/infed_pi.

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