Vitamin B12 Therapy That's Easy to Swallow

Is oral B₁₂ therapy an effective substitute for monthly injections?

Vitamin B₁₂ deficiency is common; the estimated prevalence is about 15%. It can also be cumbersome to treat. The "gold standard" for therapy has been monthly intramuscular injections of 1000 µg of vitamin B₁₂. The hidden costs of this treatment are the pain of the injections and the travel requirements for either the patient (who is often an older adult) or the visiting nurse.

AN ORAL ALTERNATIVE
What the data show. Butler and colleagues¹ suggest that 2000 µg of oral vitamin B₁₂ daily or a daily dose of 1000 µg initially followed by the same dose weekly, and finally monthly, is as effective as intramuscular B₁₂ for preventing the anemic and neurological complications of B₁₂ deficiency.^1,2 Their conclusions are based on the results of 2 studies that qualified for inclusion in their systematic review of randomized controlled trials of B₁₂ therapy.

The first study included 26 patients who received oral therapy and 34 who had intramuscular injections; the second included a total of 33 participants who were given intramuscular B₁₂ followed by oral therapy.^3,4 Primary outcomes in the 2 studies were similar; they included serum cobalamin (B₁₂) levels, hemoglobin levels, mean cell volumes, white blood cell counts, platelet counts, Mini-Mental State Examination results, neurological examination results, side-effect profiles of the 2 treatments, and methylmalonic acid (MMA) and homocysteine levels.

MMA levels were measured because determination of B₁₂ levels alone does not provide complete accuracy in the diagnosis of deficiency. Of patients with an established B₁₂ deficiency, 3% to 5% have a normal B₁₂ level (95% to 97% sensitivity); 25% to 40% of patients with a low B₁₂ level may not have deficiency (60% to 75% specificity). In contrast, measurement of MMA has greater than 90% sensitivity and probably higher than 90% specificity for detecting vitamin B₁₂ deficiency. Recent data have shown, however, that renal insufficiency can raise the MMA level in the absence of true B₁₂ deficiency.⁵

A few caveats. Although the data from these trials are promising, only the short-term effectiveness of oral therapy was addressed. In addition, the 2 studies included a total of only 93 patients.

IMPLICATIONS FOR YOUR PRACTICE
If you choose to switch from parenteral B₁₂ to an oral preparation, careful follow-up is mandatory because neurological damage can result from B₁₂ deficiency. Oral B₁₂ replacement is probably most appropriate for patients who do not want intramuscular injections, who find travel a hardship (although they must still visit the office 3 or 4 times a year for monitoring while taking oral B₁₂), and who are reliable in follow-up.

Measurement of MMA is probably the best test for the adequacy of replacement. If the level rises, a return to intramuscular dosing is necessary.