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vitamin B12

A water-soluble vitamin of animal origin required for DNA synthesis. It is a glycoprotein produced and secreted by the gastric parietal cells, and is absorbed from the GI tract bound to intrinsic factor; the body stores up to one years’ worth of vitamin B12 in the liver, kidneys and heart. Rapid cell turnover (e.g., growth spurts in children, malignancy) require increased amounts of vitamin B12. Vegans, who ingest no protein of animal origin, are at risk for vitamin B12 deficiency.

Increased by
Chronic myeloid leukaemia, chronic obstructive pulmonary disease, congestive heart failure, liver disease, obesity, polycythemia vera, renal failure.
Decreased by
Atrophic gastritis, drugs (antibiotics, anticonvulsants, antimalarials, antituberculous agents, chemotherapy, contraceptives, diuretics, oral hypoglycemics, sedatives), inflammatory bowel disease (e.g., Crohn’s disease, ulcerative colitis), intrinsic factor deficiency (causing megaloblastic anaemia), malabsorption, malnutrition, parasites (e.g., Diphyllobotrium latum), veganism.
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References in periodicals archive ?
Gabapentin (Methylcobalamin is useful for neuropathic pain).
Oxidation of the cobalt ion by [N.sub.2]O prevents methylcobalamin from acting as a coenzyme in the production of methionine and subsequently S-adenosyl-L-methionine (SAM), which is necessary for methylation of myelin sheath phospholipids (5).
Cells were spiked with methylcobalamin at clinically relevant concentrations (Table 1) and incubated for 24 hours.
In this study, mainly plasma half-life was taken for PK profile except for one combination (pregabalin + methylcobalamin) for which clinical benefit was taken into consideration because methylcobalamin (vitamin [B.sub.12]) is stored in our body.
An active form of B12 called methylcobalamin, or methyl B12, supports normal brain development by its control through a process known as epigenetic regulation of gene expression.
slow I/V daily in NSS for 5 days, Ascorbic acid 4ml I/V in DNS for 5 consecutive days and Methylcobalamin 3 ml I/M for 5 alternate days.
The cobalamin (Cbl) cofactor of MS, its Cbl[I] form, directly participates in the transfer reaction by abstracting a folate-derived methyl group, temporarily creating methylcobalamin (MeCbl), and then transferring the methyl group to HCY [1].
Absorption of cyanocobalamin, coenzyme B 12, methylcobalamin, and hydroxocobalamin at different dose levels.
(1) Folic acid is usually associated with the intracellular vitamin B12, also known as cobalamin, which presents itself in two forms of active coenzymes: methylcobalamin and desoxyadenosylcobalamin.
ALA 100 mg bid has been investigated as part of a 3-drug combination (with pregabalin 75 mg bid and methylcobalamin 750 meg bid) compared with monotherapy (pregabalin 75 mg bid) in an open randomized study (N=30) for 12 weeks.
For synthesis of methionine, a methyl group is transferred from methyltetrahydrofolate (THF) to methylcobalamin (Cbl).