Vitamin B12 Other names: Cobalamin Cyanocobalamin

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.

Deficiency is more likely in patients with malabasorption syndromes or metabolic disorders, nitrous-oxide induced megalobastosis, or following gastrectomy or extensive ileal resection. Deficiency leads to megaloblastic anaemias and demyelination and other neurological damage.

On oral intake, Vitamin B₁₂ substances bind to intrinsic factor, a glycoprotein secreted by the gastric mucosa, and are then actively absorbed from the gastrointestinal tract. A specific anaemia known as pernicious anaemia develops in patients with an absence of intrinsic factor. Absorption is also impaired in patients with disease or abnormality of the gut.

Treatment usually results in rapid haematological improvement and a striking clinical response. However, neurological symptoms respond more slowly.

Distribution

Hydroxocobalamin is extensively bound to specific plasma proteins (transcobalamins); transcobalamin II appears to be involved in the rapid transport of the cobalamins to tissues.

Elimination

Hydroxocobalamin is stored in the liver, excreted in the bile, and undergoes extensive enterohepatic recycling; part of the dose is excreted in the urine, most of it in the first 8 hours. It is stored in the liver, excreted in the bile, and undergoes enterohepatic recycling; part of a dose is excreted in the urine, most of it in the first 8 hours.

Hydroxocobalamin diffuses across the placenta and also appears in breast milk. Hydroxocobalamin is better retained than cyanocobalamin; 90% of a 100 microgram dose and 30% of a 1000 microgram dose are retained, a range believed to be sufficient for body requirements for 2 to 10 months.

There is no additional information.