Pharmacology of Methylcobalamin

Methylcobalamin (mecobalamin, MeCbl, or MeB12) is a cobalamin, a form of vitamin B12. Methylcobalamin is equivalent physiologically to vitamin B12, and can be used to prevent or treat pathology arising from a lack of vitamin B12 intake (vitamin B12 deficiency). Methylcobalamin is also used in the treatment of peripheral neuropathy, diabetic neuropathy, and as a preliminary treatment for amyotrophic lateral sclerosis.

Chemistry

Methylcobalamin is the methyl form of cobalamin obtained from hydroxycobalamin, either by chemical manipulation in the laboratory or in the body as a natural process. Cyano- and hydroxocobalamin are considered the storage or transport forms of cobalamin, while methylcobalamin and deoxyadenosylcobalamin are the active forms involved in enzymatic reactions. Methylcobalamin is involved specifically in the normal metabolism of folate and the consequent maintenance of normal homocysteine serum levels.

Pharmacology

Vitamin B12 deficiency

The prevalence of vitamin B12 deficiency among elderly Americans is thought to be about 20%.1, 5 Dietary deficiency of vitamin B12 can result from poor diets or among strict vegetarians who choose not to consume any animal products. A lack of stomach acid occurs in elderly patients and among people taking proton pump inhibitors, leading to poor digestion of the vitamin from animal products. People with a lack of intrinsic factor (also known as pernicious anemia), as well as those with severe GI disorders with impaired small intestine function (eg, Crohn disease) or those who have undergone gastric bypass surgery may also be deficient in vitamin B12.

The deficiency can lead to subtle cognitive and neurologic changes, as well as to more severe anemia and dementia.6, 7, 8 Neonatal development may also be impaired in infants breastfed by mothers who have a vitamin B12 deficiency.

Clinical data

Vitamin B12 deficiency can be corrected with the administration of cobalamin. Usually either cyano- or hydroxocobalamin is used to restore normal levels. Clinical trials specifically evaluating methylcobalamin supplementation are lacking. However, there is no reason to suggest lack of efficacy, and reports exist of therapeutic efficacy of methylcobalamin.