Anemia, Types and Iron Therapy

• Anemia is defined as hemoglobin (Hb) below the reference range, with low Hb being <13 g/dL for men and <12 g/dL for women based on WHO criteria.

Types of Anemias

• Iron deficiency anemia is a type of anemia
• Megaloblastic anemia is caused by folic acid or vitamin B12 deficiency
• Hemolytic anemia is congenital or acquired and can be caused by drug toxicity
• Aplastic anemia results from failure of bone marrow proliferation and can be due to neoplasms or drug toxicity

Iron Therapy

• Iron needs to be converted into a ferrous state to be properly absorbed
• Absorption happens in the duodenum and proximal jejunum
• Vitamin C, anemia, HCL, pregnancy and infancy all increase iron absorption.
• Antacids, tetracyclines, tannic acid, and desferrioxamine all decrease iron absorption

Indications of Iron Therapy

• Iron deficiency anemia (hypochromic microcytic)
• Treatment of megaloblastic anemia and anemia of chronic renal failure due to depletion of iron stores from increased RBCs synthesis.

Iron Preparations

Oral Iron Therapy

• Ferrous iron is efficiently absorbed.
• Ferrous sulfate, ferrous gluconate, and ferrous fumarate are effective and recommended
• The daily dose for adults with iron deficiency is 150-200 mg/day of elemental iron
• Example: 200mg (=65mg elemental iron) ferrous sulphate t.d.s.
• Reticulocytosis starts in about 7 days, with Hb rising by about 2 g/dL over three weeks
• Hemoglobin level should be normal between 1-3 months
• Treatment with oral iron should continue for 6 months after hemoglobin reaches normal to replenish iron stores.

Side Effects of Iron Therapy

• 20%-25% of patients on iron therapy will have Gl side effects
• abdominal bloating, pain, nausea, vomiting, diarrhea/constipation
• Reducing elemental iron concentration may avoid side effects
• Dark stools can obscure GI blood loss diagnosis (melena)

Parenteral Iron Therapy

• Mobilization of iron from intramuscular sites is slow and incomplete
• Hemoglobin concentration rises only slightly faster than with oral iron
• Indicated when iron deficiency is untolerated or unable to be absorbed
• Severe anemia or continuous chronic blood loss cannot be corrected by oral iron
• Iron dextran complex is given via I.V. injection
• Iron sucrose (Venofer®) IV is effective and has a lower risk of anaphylaxis compared to iron dextran

Side Effects of Parenteral Iron Therapy

• Local pain and tissue staining with I.M. Injection (brown discoloration of the tissues overlying the injection site)
• Headache, fever, joint pain, muscle pain
• Urticaria, bronchospasm and rarely anaphylaxis
• A small test dose of iron dextran should be given 30-60 minutes prior to the full dose.

Iron Toxicity

• Fatal overdose can occur especially in children
• Deferroxamine is used for iron overdose
• It is an iron-chelating agent
• It binds to iron, assisting with its excretion and can be given systematically or via gastric lavage

Vitamin B12

• Parietal cells of gastric mucosa secrete intrinsic factor, which is essential for the absorption of vitamin B12
• Absorption takes place mainly in the terminal ileum
• Hydroxocobalamin dose is 1000 µg (1 mg) IM every day for one week, followed by 1 mg every week for four weeks then, if the underlying disorder persists, as in PA, 1 mg every month for life

Indications for B12 Use

• Vitamin B12 deficiency
• Pernicious anemia
• Malabsorption syndromes are indications
• Drugs causing malabsorption of vitamin B12 e.g. antiretroviral and metformin
• Peripheral neuropathy especially in diabetes mellitus
• Hydroxycobalamin is useful in cyanide poisoning.
• Hydroxycobalamin combines with cyanide to form cyanocobalamin, which is renally cleared

Folic Acid (vitamin B9)

• Dosage is 1 to 5 mg/day PO for one to four months, or until complete hematologic recovery occurs.

Indications

• Megaloblastic anemia
• Malabsorption syndrome
• Pregnancy, folate requirement is increased from 400µg to 800µg/day
• Prevention of fetal neural tube defect (spina bifida)
• With drug-induced folate deficiency: e.g., phenytoin and trimethoprim

Erythropoietin

• Erythropoietin is effective in the management of anemia from chronic renal failure
• The hormone has also been used in severe anemia of cancer
• Erythropoietin needs to be given IM or S.C

Adverse Effects

• Iron deficiency may occur in the patient with chronic renal failure
• Increased hemopoiesis depletes iron stores
• Increased blood viscosity, increasing risk of VTE
• Hypertension is due to rapid increase in RBCs and blood viscosity
• Red cell aplasia occurs when antibodies are directed against the EPO molecule (rare but necessitates ceasing the treatment)

This lesson describes anemia, its types (iron deficiency, megaloblastic, hemolytic, aplastic). It also covers iron therapy, including factors affecting iron absorption and indications for iron therapy.