Vitamin B12 Deficiency - Treatment

Treatment

B₁₂ can be supplemented in healthy subjects by oral pill; sublingual pill, liquid, or strip; intranasal spray; transdermal patch or by injection. B₁₂ is available singly or in combination with other supplements. B₁₂ supplements are available in forms including cyanocobalamin, hydroxocobalamin, methylcobalamin, and adenosylcobalamin (sometimes called "cobamamide" or "dibencozide"). Oral treatments involve giving 250 µg to 1 mg of B₁₂ daily.

Vitamin B₁₂ can be given as intramuscular or subcutaneous injections of hydroxycobalamin, methylcobalamin, or cyanocobalamin. Body stores (in the liver) are partly repleted with half a dozen injections in the first couple of weeks (full repletion of liver stores requires about 20 injections) and then maintenance with monthly injections throughout the life of the patient. Vitamin B₁₂ can also be easily self-administered by injection by the patient, using the same fine-gauge needles and syringes used for self-administration of insulin.

B₁₂ has traditionally been given parenterally (by injection) to ensure absorption. However, oral replacement is now an accepted route, as it has become increasingly appreciated that sufficient quantities of B₁₂ are absorbed when large doses are given. This absorption does not rely on the presence of intrinsic factor or an intact ileum. Generally 1 to 2 mg daily is required as a large dose. By contrast, the typical Western diet contains 5–7 µg of B₁₂ (Food and Drug Administration (FDA) Daily Value ). It has been appreciated since the 1960s that B₁₂ deficiency in adults resulting from malabsorption (including loss of intrinsic factor) can be treated with oral B₁₂ supplements when given in sufficient doses. When given in oral doses ranging from 0.1–2 mg daily, B₁₂ can be absorbed in a pathway that does not require an intact ileum or intrinsic factor. In two studies, oral treatment with 2 mg per day was as effective as monthly 1 mg injections.

Hypokalemia, an excessively low potassium level in the blood, is anecdotally reported as a complication of vitamin B₁₂ repletion after deficiency. Excessive quantities of potassium are used by newly growing and dividing hematopoietic cells, depleting circulating stores of the mineral.

Research has established the effectiveness of other routes of B₁₂ administration, primarily intranasal and sublingual dosing, but neither has been proven to be superior to oral dosing; recommendations are based on a consumers individual circumstances. The sublingual route, in which B₁₂ is absorbed under the tongue, is manufactured in a variety of forms, such as lozenges, pills, and lollipops. A 2003 study found no significant difference in absorption for serum levels from oral vs. sublingual delivery of 500 µg (micrograms) of cobalamin, although the study measured only serum levels as opposed to tissue levels, which is more reflective of B₁₂ levels. Sublingual methods of replacement may be effective only because of the typically high doses (500 micrograms), which are swallowed, not because of placement of the tablet. As noted below, such very high doses of oral B₁₂ may be effective as treatments, even if gastro-intestinal tract absorption is impaired by gastric atrophy (pernicious anemia).