vitamin B12
vitamin B12 mechanism of action
impaired absorption of vitamin B12: - GI malabsorption syndrome (celiac disease) - elevated gastric pH (H2 receptor blockers: ranitidine) - lack of intrinsic factor (pernicious anemia) vitamin B12: - converts folic acid into its active form for DNA synthesis - neurological system & blood cell forming organs primarily affected
vitamin B12 prototype
vitamin B12, cyanocobalamin (nascobal)
vitamin B12 side & adverse effects
diarrhea hypokalemia
vitamin B12 precautions
- cardiovascular disease - pulmonary disease - other types of anemia - concurrent folic acid use
vitamin B12 interactions
- folic acid can mask the symptoms of vitamin B12 deficiency; pts. must take adequate doses of cyanocobalamin - chloramphenicol (chloromycetin) decreases effectiveness - alcohol, neomycin (mycifradin), colchicine (colcrys), and aminosalicylic acid (paser) reduce the absorption of oral forms - ascorbic acid (vitamin c) alters the stability of oral forms
vitamin B12 administration
- give orally, subcutaneously, IM or intranasally - for oral dosing, confirm gastric absorption of B12 via schilling test - give intranasally or parentally to pts. who have malabsorption syndrome - give intranasally 1 hr before or after hot foods - give oral forms with food to enhance absorption - obtain baseline vitamin B12, Hgb, Hct, RBC, and reticulocyte count - expect lifelong treatment for pts. who have irreversible B12 deficiencies - encourage dietary intake of foods high in vitamin B12
vitamin B12 client education
- increase fluid intake - diarrhea diminishes as drug therapy continues - report persistent diarrhea - report muscle weakness, nausea, palpitations or paresthesias - ensure pt. understands how to take vitamin B12 & the need to have periodic laboratory values drawn
vitamin B12 interventions
- monitor bowel patterns - maintain hydration - monitor potassium levels - monitor for potassium deficiency (muscle weakness, cardiac dysrhythmias) - recommend potassium supplements for prevention or treatment of hypokalemia
vitamin B12 uses
- pernicious anemia: lack of intrinsic factor - vitamin B12 deficiency: due to either malabsorption or dietary deficiency
vitamin B12 contraindications
- sensitivity to cobalt, vitamin B12, other colbalamins - hereditary optic nerve atrophy
