indication

For treatment of pernicious anemia (due to lack of or inhibition of intrinsic factor) and for prevention and treatment of vitamin B 12 deficiency.

pharmacology

Cyanocobalamin (Vitamin B12) is a water-soluble organometallic compound with a trivalent cobalt ion bound inside a corrin ring. It is needed for nerve cells and red blood cells, and to make DNA. Vitamin B12 deficiency is the cause of several forms of anemia.

mechanism of action

Vitamin B12 is used in the body in two forms: Methylcobalamin and 5-deoxyadenosyl cobalamin. The enzyme methionine synthase needs methylcobalamin as a cofactor. This enzyme is involved in the conversion of the amino acid homocysteine into methionine. Methionine in turn is required for DNA methylation. 5-Deoxyadenosyl cobalamin is a cofactor needed by the enzyme that converts L-methylmalonyl-CoA to succinyl-CoA. This conversion is an important step in the extraction of energy from proteins and fats. Furthermore, succinyl CoA is necessary for the production of hemoglobin, the substances that carries oxygen in red blood cells.

toxicity

Anaphylactic reaction (skin rash, itching, wheezing)-after parenteral administration. ORL-MUS LD₅₀ > 8000 mg/kg

biotransformation

Hepatic

absorption

Readily absorbed in the lower half of the ileum.

half life

Approximately 6 days (400 days in the liver).