Cyanocobalamin (Vitamin B12)

Indications

Cyanocobalamin (Vitamin B12) is used for: Pernicious anemia, Vitamin B12 deficiency due to low intake from food, Thyrotoxicosis, Hemorrhage, Malignancy, Liver or kidney disease, Gastric bypass surgery, Total or partial gastrectomy, Gluten enteropathy or sprue, Folic acid deficiency, Macrocytic anaemia

Adult Dose

Intramuscular Pernicious or macrocytic anaemia Adult: 250-1000 mcg, given on alternate days for 1-2 wk, then 250 mcg wkly until the blood count returns to normal. Maintenance doses: 1000 mcg, given every mth. Hepatic impairment: Increased requirement in hepatic impairment.

Child Dose

Renal Dose

Renal impairment: Increased requirement in renal impairment.

Administration

Contra Indications

Leber's disease, tobacco amblyopia.

Precautions

Intensive treatment of B12-deficient megaloblastic anemia may cause hypokalemia and sudden death Nasal disease; defer use until symptoms resolve Use with caution in patients with Leber optic nerve atrophy Thrombocytosis may occur with treatment of severe vitamin B12 megaloblastic anemia Lactation: Drug distributed in milk; safe to use

Pregnancy-Lactation

Pregnancy category: A; C (for doses exceeding RDA and for intranasal products) Lactation: Drug distributed in milk; safe to use

Interactions

Absorption reduced by antibiotics, aminosalicylic acid, anticonvulsants, biguanides, cholestyramine, cimetidine, colchicine, K salts, methyldopa.

Adverse Effects

Side effects of Cyanocobalamin (Vitamin B12) : >10% Arthralgia (12%), Dizziness (12%), Headache (12%), Nasopharyngitis (12%) Frequency Not Defined Anaphylaxis, Angioedema, Congestive heart failure, Peripheral vascular disease, Pulmonary edema, Diarrhea, Dyspepsia, Polycythemia vera, Sore throat, Nervousness, Rhinitis, Glossitis, Hypoesthesia

Mechanism of Action

Vitamin B12 (cyanocobalamin): Required for the maintenance of normal erthropoiesis, nucleprotein and myelin synthesis, cell reproduction and normal growth; Coenzyme; metabolic functions include protein synthesis and carbohydrate metabolism. Plays role in cell replication and hematopoiesis.