Vitamin B12 is made up of a porphyrin-like ring with a central cobalt atom attached to a nucleotide. Daily vitamin B12 requirement is 2-5 mg. It is mainly obtained from animal products and serves as a co factor for essential biochemical reaction in humans. Ultimate source of vit B12 is from microbial synthesis.
Pharmacokinetics
Absorbed in distal ileum after combined with intrinsic factor secreted by stomach through a highly specific receptor mediated transport system once absorbed vit B 12 is transported to various cells of the body bound to plasma glycoprotein, transcobalamin II. Excess vitamin B12 is transported to the liver for storage and excreted in the urine.
Physiologic function
- Acts as a coenzyme in the synthesis of DNA and is also essential for various metabolisms in the body.
Clinical uses
- Vit B12 is used to treat or prevent deficiency of vit B 12
Deficiency of Vit B 12 results in:
- Megaloblastic anemia
- Neurological syndrome involving spinal cord and peripheral nerves
Causes:
The causes for Pernicious anemia are defective secretion of intrinsic factor necessary for absorption of vitB 12, partial or total gastrectomy, diseases that affect distal ileum, malabsoption syndrome e.g inflammatory bowel disease, small bowel resection etc.
Almost all cases of vit B12 deficiencies are caused by malabsorption
Treatment
Vit B12 therapeutic preparations are cyanocoblamin and hydroxycobalamin and For intrinsic factor deficiency the vitamin should be given parenterally and patients with pernicious anemia will need life-long therapy.
Leave a Reply