Cyanocobalamin is indicated for the treatment of pernicious anemia and vitamin B12 deficiency, particularly when caused by inadequate dietary intake or impaired absorption. It may also be used in conditions such as macrocytic anemia and malabsorption disorders, including gluten enteropathy (sprue). Supplementation is often required after gastric bypass surgery or total or partial gastrectomy. In certain cases, it may be given as supportive therapy in conditions like hemorrhage, malignancy, liver or kidney disease, and folic acid deficiency when associated with vitamin B12 deficiency.

Cyanocobalamin (vitamin B12) plays an essential role in maintaining normal erythropoiesis, as well as in nucleoprotein and myelin synthesis. It is necessary for cell reproduction, normal growth, and proper neurological function. Acting as a coenzyme, it is involved in key metabolic processes such as protein synthesis and carbohydrate metabolism. It also contributes significantly to cell replication and hematopoiesis.

Usual Adult Dose for Pernicious Anemia

Initial dose: 1000 mcg intramuscularly or deep subcutaneous once a day for 6 to 7 days

If clinical improvement and reticulocyte response is seen from the above dosing:

• 100 mcg every other day for 7 doses, then
• 100 mcg every 3 to 4 days for 2 to 3 weeks, then
• Maintenance dose: 100 to 1000 mcg monthly

Administer concomitant folic acid if needed. Chronic treatment should be done with an oral preparation in patients with normal intestinal absorption.

Usual Adult Dose for B12 Nutritional Deficiency 25 to 2000 mcg orally daily

Usual Adult Dose for Schilling Test 1000 mcg intramuscularly is the flushing dose

Usual Pediatric Dose for B12 Nutritional Deficiency 0.5 to 3 mcg daily

Absorption of the drug may be reduced when used with antibiotics, aminosalicylic acid, anticonvulsants, biguanides, cholestyramine, cimetidine, colchicine, potassium salts, and methyldopa.

Contraindicated in patients with Leber’s disease and tobacco amblyopia.

Common and reported adverse effects include arthralgia (12%), dizziness (12%), headache (12%), nasopharyngitis (12%), anaphylaxis, angioedema, congestive heart failure, peripheral vascular disease, pulmonary edema, diarrhea, dyspepsia, polycythemia vera, sore throat, nervousness, rhinitis, glossitis, and hypoesthesia.

Pregnancy Category A. Well-controlled studies in humans have not shown any risk to the fetus during the first trimester, and no evidence of harm has been observed in later stages of pregnancy. The drug is excreted in breast milk.

Intensive treatment of vitamin B12-deficient megaloblastic anemia may lead to hypokalemia and sudden death. Use caution in patients with Leber optic nerve atrophy. Thrombocytosis may occur during treatment of severe vitamin B12 deficiency.

Vitamin B preparations