Vitamin B12 deficiency medical therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Medical Therapy

Pharmacotherapy

Moderate filiform taste bud atrophy thought to be due to a vitamin B12, or iron deficiency‎

B₁₂can be supplemented in healthy subjects by oral pill; sublingual pill, liquid, or strip; 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").

Vitamin B₁₂can be given as intramuscular injections of hydroxycobalamin, methylcobalamin, or cyanocobalamin. Body stores (in the liver) are refilled with half a dozen injections in the first couple of weeks and then maintenance with monthly to quarterly injections throughout the life of the patient.

B₁₂has traditionally been given parenterally to ensure absorption in the dosage of 1 mg qd x 1 wk, then qwk x 1month, then monthly. However, oral replacement is now an accepted route, as it has become increasingly appreciated that sufficient quantities of B₁₂are absorbed when large doses are given although this is a less efficient path for absorption (1%). 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 ). This method may be more effective than IM Rx, but requires patient compliance.

Hypokalemia, an excessive low potassium level in the blood, is anecdotally reported as a complication of vitamin B₁₂repletion after deficiency. Excessive quantities of potassium are used by newly growing and dividing hematopoeitic cells, depleting circulating stores of the mineral.

It has been appreciated since the 1960s that deficiency can sometimes be treated with oral B₁₂supplements when given in sufficient doses. When given in oral doses ranging from 0.1–2 mg daily, B₁₂can be absorbed in a pathway that does not require an intact ileum or intrinsic factor. However, with the advent of sublingual and intranasal administration, tablet usage is becoming outdated. Oral absorption is limited so regular intramuscular injections or sublingual/intranasal administration of a cobalamin (preferably methyl- or hydroxycobalamin) is necessary to restore systemic stores to physiological levels. Recent research indicates that sublingual administration eliminates a deficiency as well as injections with the advantage of evading the allergy risk.