Oral B12: the best kept secret in medicine – pro
- Because most clinicians are generally unaware that oral vitamin B12 therapy is effective the traditional treatment for B12 deficiency has bee
- B12 deficiency is common. The etology of B12 deficiency should be discovered in order to plan treatment and for prognosis but very often it is empirically treated becasue B12 is inexpensive and easy to administer and the diagnostic workup is complex and expensive.
- n intramuscular injections. However, since as early as 1968, oral vitamin B12 has been shown to have an efficacy equal to that of injections in the treatment of pernicious anemia and other B12 deficiency. Although the majority of dietary vitamin B12is absorbed in the terminal ileum through a complex with intrinsic factor, evidence for the previously mentioned alternate transport system is mounting.In one study, 38 patients with vitamin B12 deficiency were randomized to receive oral or parenteral therapy. Patients in the parenteral therapy group received 1,000 mcg of vitamin B12 intramuscularly on days 1, 3, 7, 10, 14, 21, 30, 60, and 90, while those in the oral treatment group received 2,000 mcg daily for 120 days. At the end of 120 days, patients who received oral therapy had significantly higher serum vitamin B12 levels and lower methylmalonic acid levels than those in the parenteral therapy group. The actual transport mechanism used in this pathway remains unproved, but vitamin B12 is thought to be absorbed “en masse” in high doses. Surprisingly, one study showed that even in patients who had undergone gastrectomy, vitamin B12deficiency could be easily reversed with oral supplementation.Intramuscular injections, although safe and inexpensive, have several drawbacks. Injections are painful, medical personnel giving the injections are placed at risk of needlestick injuries, and administration of intramuscular injections often adds to the cost of therapy. Treatment schedules for intramuscular administration vary widely but usually consist of initial loading doses followed by monthly maintenance injections. One regimen consists of daily injections of 1,000 mcg for one to two weeks, then a maintenance dose of 1,000 mcg every one to three months.
Although the daily requirement of vitamin B12 is approximately 2 mcg, the initial oral replacement dosage consists of a single daily dose of 1,000 to 2,000 mcg. This high dose is required because of the variable absorption of oral vitamin B12 in doses of 500 mcg or less.19 This regimen has been shown to be safe, cost-effective, and well tolerated by patients.
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- Adachi S, Kawamoto T, Otsuka M, Fukao K. Enteral vitamin B12 supplements reverse postgastrectomy B12 deficiency. Ann Surg 2000;232:199-201.
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- Oberley MJ, Yang DT. Laboratory testing for cobalamin deficiency in megaloblastic anemia. Am J Hematol 2013; 88:522.
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