Cyanocobalamin (vitamin B12)

Cyanocobalamin or vitamin-B12 is an essential vitamin of the B-complex. It is required by animals that use it as a cofactor in DNA synthesis and in fatty acid and amino acid metabolism. It is important for the normal functioning of the nervous system through its role in the synthesis of myelin and in the circulatory system during the maturation of red blood cells in the bone marrow.

As a drug, it is given for vitamin B12 deficiency, also called pernicious anemia. It can be administered intravenously, perorally or as a nasal spray. In addition, it can be administered in highly concentrated form as an antidote in the event of cyanide poisoning.

Pharmacodynamics

Cyanocobalamin as a drug corrects vitamin B12 deficiency and rapidly improves symptoms associated with pernicious anemia.

In cyanide poisoning, the derivative hydroxycobalamin is usually given. Hydroxycobalamin binds the toxic cyanide ion, producing the nontoxic cyanocobalamin. This is then excreted in the urine.

Vitamin B12 serves as a cofactor for the enzymes methionine synthase and L-methylmalonyl-CoA mutase. Methionine synthase is essential for the synthesis of purines and pyrimidines, which form DNA. L-methylmalonyl-CoA mutase converts L-methylmalonyl-CoA to succinyl-CoA upon degradation of propionate, an important reaction required for both lipid and protein metabolism.

Pharmacokinetics

Vitamin B12 is rapidly absorbed from intramuscular and subcutaneous injection sites, with peak plasma concentrations reached approximately 1 hour after injection. Cyanocobalamin is excreted by both the kidneys and bile. The half-life is about 6 days and I stored form in the liver even up to 400 days.

Side effects

Since vitamin B12 occurs naturally in the body, side effects are unlikely at normal and increased doses.

Toxicological Data

LD50: Oral (mouse): > 5,000 mg/kg