Anemia: Types and Iron Therapy

• Anemia is when hemoglobin (Hb) is below the reference range; less than 13 g/dL for men and less than 12 g/dL for women (WHO criteria).

Types of Anemias

• Iron deficiency anemia is one type.
• Megaloblastic anemia results from folic acid or vitamin B12 deficiency.
• Hemolytic anemia can be congenital or acquired, such as from drug toxicity.
• Aplastic anemia involves bone marrow failure caused by neoplasms or drug toxicity.

Iron therapy

• Conversion to a ferrous state is required for iron absorption.
• Absorption takes place in the duodenum and proximal jejunum.
• Vitamin C, anemia, HCL, pregnancy, and infancy increase iron absorption.
• Antacids, tetracyclines, tannic acid (strong tea), and desferrioxamine decrease iron absorption.
• Iron therapy is indicated for iron deficiency anemia (hypochromic microcytic).
• It is also indicated during treatment of megaloblastic anemia and anemia of chronic renal failure.
• Supplemental iron is needed in these instances because iron stores become depleted by rapid red blood cell synthesis.

Oral Iron Therapy

• Ferrous salts should be used because ferrous iron is absorbed most efficiently.
• Ferrous sulfate, ferrous gluconate, and ferrous fumarate are effective and recommended for treating most patients.
• The recommended daily dose for adults with iron deficiency is 150-200 mg/day of elemental iron.
• For example: 200mg of ferrous sulfate t.d.s. contains 65mg of elemental iron.
• Reticulocytosis starts in approximately 7 days, with Hb rising about 2 g/dL over three weeks.
• Hemoglobin levels should normalize in 1-3 months.
• Continue treatment with oral iron for 6 months after hemoglobin levels normalize to replenish iron stores.
• 20-25% of iron therapy patients experience gastrointestinal side effects (abdominal bloating, pain, nausea, vomiting, diarrhea/constipation).
• Reducing elemental iron concentration per dose can mitigate these effects.
• Dark stools, which may obscure diagnosis of GIT blood loss (melena), are a side effect.

Parenteral Iron Therapy

• Iron mobilization from intramuscular sites is slow and sometimes incomplete.
• Hemoglobin concentration rises only slightly faster compared to oral iron.
• Indications include iron deficiency with intolerance or malabsorption, severe anemia, or extensive chronic blood loss that cannot be corrected by oral iron.
• Iron dextran complex can be administered via I.V. injection
• Iron sucrose (Venofer®) IV is also effective and poses a low risk of anaphylaxis compared to iron dextran.
• Local pain and tissue staining can occur with I.M. injection.
• This causes brown discoloration of tissues overlying the injection site.
• Headache, fever, joint or muscle pain are other side effects.
• Urticaria, bronchospasm, and rarely, anaphylaxis can occur.
• Administer a small test does of iron dextran 30-60 minutes before the full dose.

Iron Toxicity

• Fatal overdose is possible, especially in children.
• Deferroxamine is used to address iron overdose as an iron-chelating agent.
• It binds to iron, promoting its excretion, and can be given systemically or via gastric lavage.

Vitamin B12

• Parietal cells in the gastric mucosa secrete intrinsic factor, essential for vitamin B12 absorption.
• Absorption primarily occurs in the terminal ileum.
• Administer hydroxocobalamin at a dose of 1000 µg (1 mg) IM daily for one week, then 1 mg every week for four weeks.
• If the underlying disorder persists, as in pernicious anemia, maintain 1 mg monthly for life.
• Vitamin B12 supplements are indicated for: -Pernicious anemia. -Malabsorption syndromes. -Malabsorption-causing drugs like antiretrovirals and metformin. -Peripheral neuropathy, especially in diabetes mellitus. -Cyanide poisoning: hydroxocobalamin combines with cyanide to form cyanocobalamin, which is renally cleared.

Folic Acid (Vitamin B9)

• Administer folic acid (1 to 5 mg/day PO) for one to four months or until complete hematologic recovery.
• Folic acid is indicated in megaloblastic anemia, malabsorption syndrome, and during pregnancy.
• Pregnancy increases folate requirements from 400µg to 800µg/day.
• Folic acid can help prevent fetal neural tube defects (spina bifida).
• It is also indicated for drug-induced folate deficiency, such as with phenytoin and trimethoprim.

Erythropoietin

• Erythropoietin is effective in managing anemia of chronic renal failure.
• Used in severe anemia of cancer.
• Erythropoietin should be administered IM or subcutaneously (S.C).

Adverse Effects of Erythropoietin

• Iron deficiency may occur in chronic renal failure patients because increased hemopoiesis depletes iron stores.
• Increased blood viscosity may occur.
• The risk of VTE increases.
• Hypertension can occur due to a rapid increase in RBCs and blood viscosity.
• Red cell aplasia can occur due to antibodies against the EPO molecule.
• It is a rare occurrence but necessitates stopping treatment.