Cached July 10 2003

Classification: Vitamin B12 
 

Action/Kinetics: Required for hematopoiesis, cell reproduction, nucleoprotein and myelin synthesis. Plasma vitamin B12 levels: 150-750 pg/mL. Rapidly absorbed following IM or SC administration. Following absorption, vitamin B12 is carried by plasma proteins to the liver where it is stored until required for various metabolic functions. t1/2: 6 days (400 days in the liver). Time to peak levels, after PO: 8-12 hr. 
 

Uses: Cyanocobalamin Gel/Tablets: Nutritional vitamin B12 deficiency; not to be used for treatment of pernicious anemia. Cyanocobalamin Parenteral: Vitamin B12 deficiency due to malabsorption syndrome as seen in pernicious anemia. GI pathology, dysfunction, or surgery. Fish tapeworm infestation, maligancy of pancreas or bowel, gluten enteropathy, small bowel overgrowth of bacteria, sprue, accompanying folic acid deficiency, or total or partial gastrectomy. 
 

Contraindications: Hypersensitivity to cobalt, Leber's disease. 
 

Special Concerns: Use with caution in clients with gout. 
 

Side Effects: Following parenteral use. Allergic: Urticaria, itching, transitory exanthema, anaphylaxis, shock, death. CV: Peripheral vascular thrombosis CHF, pulmonary edema. Other: Polycythemia vera, optic nerve atrophy in clients with hereditary optic nerve atrophy, diarrhea, hypokalemia, body feels swollen. 
Following intranasal use. GI: Glossitis, N&V. Miscellaneous: Asthenia, headache, infection (sore throat, common cold), paresthesia, rhinitis.
 

NOTE: Benzyl alcohol, which is present in certain products, may cause a fatal ``gasping syndrome'' in premature infants. 

Laboratory Test Alterations: Antibiotics, methotrexate, or pyrimethamine invalidate folic acid and vitamin B12 diagnostic blood assays. 
 

Drug Interactions: Alcohol /  Vitamin B12 absorption Aminosalicylic acid /  Vitamin B12 effect. Also, abnormal Schilling test and symptoms of vitamin B12 deficiency Chloramphenicol /  Response to vitamin B12 in pernicious anemia Cholestyramine /  Vitamin B12 absorption Cimetidine /  Digestion and release of vitamin B12 Colchicine /  Vitamin B12 absorption Neomycin /  Vitamin B12 absorptionPAS /  Vitamin B12 absorption Potassium, timed-release /  Vitamin B12 absorption 
 

How Supplied: Cyanocobalamin: Gel: 400 mcg/unit, 500 mcg/0.1 mL; Tablet: 25 mcg, 50 mcg, 100 mcg, 250 mcg; Cyanocobalamin crystalline: Injection:100 mcg/mL, 1,000 mcg/mL; Tablets; 500 mcg, 1000 mcg 
 

Dosage 
Cyanocobalamin •Tablets Nutritional supplement. 
Adults: 1 mcg/day (up to 25 mcg for increased requirements). The RDA is 2 mcg/day. Pediatric, up to 1 year: 0.3 mcg/day; over 1 year: 1 mcg/day.
Nutritional deficiency. 
25-250 mcg/day.
•Nasal gel Nutritional deficiency. 
500 mcg/0.1 mL weekly given intranasally. 
Cyanocobalamin crystalline •IM, Deep SC Addisonian pernicious anemia. 
Adults: 100 mcg/day for 6-7 days; then, if improvement is noted along with a reticulocyte response, give 100 mcg every other day for seven doses and then 100 mcg q 3-4 days for 2-3 weeks. Maintenance, IM: 100 mcg once a month for life. Give folic acid if necessary.
Vitamin B12 deficiency. 
Adults: 30 mcg daily for 5-10 days; then 100-200 mcg/month. Doses up to 1,000 mcg have been recommended. Pediatric, for hematologic signs: 10-50 mcg/day for 5-10 days followed by 100-250 mcg/dose q 2-4 weeks. Pediatric, for neurologic signs: 100 mcg/day for 10-15 days; then 1-2 times/week for several months (can possibly be tapered to 250-1,000 mcg/month by 1 year).
Diagnosis of vitamin B12 deficiency. 
Adults: 1 mcg/day IM for 10 days plus low dietary folic acid and vitamin B12. Loading dose for the Schilling test is 1,000 mcg given IM.