Vitamin B12 helps activate folic acid, an essential component for DNA synthesis and cell growth and division. This vitamin is activated by intrinsic factor secreted by stomach parietal cells. Vitamin B12 is essential for proper cell growth and division, especially in the bone marrow, GI tract, and nervous system.
Vitamin B12 deficiency is commonly caused by impaired absorption related to celiac disease or low gastric acidity. Vitamin B12 deficiency causes neuronal demyelination and may lead to irreversible neurological damage. A lack of this vitamin prevents folic acid activation and leads to underproduction of white blood cells and platelets. Since humans cannot biosynthesize this vitamin, patients deficient in vitamin B12 must consume animal products, vitamin B12-fortified food, or a supplement.
Pernicious anemia is a potentially fatal condition caused by a lack of intrinsic factor necessary for vitamin B12 absorption. Administering cyanocobalamin (cobalamin) in patients lacking the intrinsic factor helps normalize the production of red blood cells and quickly reverses the effects of anemia.
Cobalamin increases the production of erythrocytes, which require potassium for synthesis. As more potassium is used for erythrocyte production, the level of serum potassium decreases and results in hypokalemia. Assess the patient for weakness, cramping, and abnormal arrhythmias.
Arthralgia, or joint pain, may be a side effect of cobalamin therapy. Assess the patient's level of pain.
Cobalamin may lead to dizziness, weakness, or headache. Severe dizziness may be related to a serious allergic reaction and requires immediate medical attention.
Cobalamin may be administered via IM injection for patients with pernicious anemia related to a lack of intrinsic factor or parietal cell atrophy. Patients with B12 malabsorption may require lifelong cobalamin therapy. Although injecting this drug is generally well tolerated, the patient may experience some pain or redness at the injection site. It can also be given as a deep subcutaneous injection.
Cobalamin may be administered orally, parenterally (IM or deep SQ injection), or intranasally. Since cobalamin is a water-soluble vitamin, do not administer intravenously due to rapid urine excretion resulting in minimal therapeutic effect.
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