ATC Group: B03BA Vitamin B12 (cyanocobalamin and analogues)

Methylcobalamin is a cobalamin, a form of vitamin B12. Mecobalamin is a kind of endogenous coenzyme B₁₂. Mecobalamin plays an important role in transmethylation as a coenzyme of methionine synthetase in the synthesis of methionine from homocysteine. Mecobalamin promotes axonal transport and axonal regeneration. Mecobalamin promotes myelination (phospholipid synthesis). Methylcobalamin is used in the treatment of peripheral neuropathy, diabetic neuropathy, and as a preliminary treatment for amyotrophic lateral sclerosis.

Hydroxocobalamin is used in the treatment and prevention of Vitamin B12 deficiency. For adults, the daily requirement of Vitamin B12 is probably about 1 to 2 micrograms and this amount is present in most normal diets. However, Vitamin B12 only occurs in animal products, not in vegetables, and therefore strict vegetarian or vegan diets that exclude dairy products may provide an inadequate amount, although a deficiency may not be apparent for many years.

Hydroxocobalamin is a cyanide antidote. Its action in the treatment of cyanide poisoning is based on its ability to bind cyanide ions. Each hydroxocobalamin molecule can bind one cyanide ion by substituting it for the hydroxo ligand linked to the trivalent cobalt ion, to form cyanocobalamin, which is then excreted in the urine.