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BLOOD AND BLOOD FORMING ORGANS › ANTIANEMIC PREPARATIONS › VITAMIN B12 AND FOLIC ACID › Vitamin B12 (cyanocobalamin and analogues)
cyanocobalamin
B03BA01
Forms & Strengths
- Injectable solution: 1,000 mcg/mL
- Oral tablet: 50 mcg, 100 mcg, 250 mcg, 500 mcg, 1,000 mcg
- Sublingual tablet: 500 mcg, 1,000 mcg, 2,500 mcg
- Nasal spray: 500 mcg/actuation
Adult Dosing
- Vitamin B12 deficiency (pernicious anemia): Intramuscular or subcutaneous 100 mcg daily for 6 to 7 days, then 100 mcg monthly for maintenance
- Severe deficiency with neurologic manifestations: 1,000 mcg IM daily for 1 to 2 weeks, then 1,000 mcg weekly for 1 month, then 1,000 mcg monthly
- Dietary supplement / Mild deficiency: Oral 50 to 2,000 mcg daily
- Nasal maintenance therapy: 500 mcg in one nostril once weekly
Pediatric Dosing
- Vitamin B12 deficiency (pernicious anemia): Intramuscular or subcutaneous 30 to 50 mcg daily up to a total of 1,000 mcg over 2 or more weeks, then 100 mcg monthly
- Dietary supplement: Oral 5 to 50 mcg daily depending on age and dietary intake
Indications
- Treatment of vitamin B12 deficiency due to malabsorption, dietary inadequacy, or pernicious anemia
- Prevention of vitamin B12 deficiency in strict vegetarians and vegans
- Diagnostic test for vitamin B12 deficiency (Schilling test adjunct)
- Metabolic disorders responsive to vitamin B12
Mechanism of Action
- Coenzyme for metabolic functions including fat and carbohydrate metabolism and protein synthesis
- Essential for cell replication, hematopoiesis, and myelin synthesis
- Converts methylmalonyl-coenzyme A to succinyl-coenzyme A and participates in the conversion of homocysteine to methionine
Contraindications
- Hypersensitivity to cyanocobalamin, cobalt, or any component of the formulation
- Early Leber's disease (hereditary optic nerve atrophy), as administration may accelerate optic atrophy
Adverse Reactions
- Anaphylaxis and hypersensitivity reactions (rare)
- Injection site pain, pruritus, or transient local irritation
- Polycythemia vera secondary to hematopoietic response
- Diarrhea, nausea, vomiting, or dizziness
- Hypokalemia during initial treatment of severe megaloblastic anemia due to rapid erythrocyte uptake
Drug Interactions
- Chloramphenicol: May antagonize the hematopoietic response to cyanocobalamin
- Colchicine, aminosalicylic acid, and biguanides (metformin): May decrease oral absorption of vitamin B12
- Histamine H2-receptor antagonists and proton pump inhibitors: Can impair absorption of protein-bound dietary vitamin B12
- Alcohol (heavy intake): May decrease absorption and effectiveness of cyanocobalamin
Curated Content: Needs Vetting Before Put to Clinical Use