Oral Cobalamin for Pernicious Anemia

THE TREATMENT of pernicious anemia with cobalamin is one of medicine's great success stories. However, the usual practice of giving the drug as an intramuscular injection has several drawbacks. Injections can be painful, difficult to provide for some patients who are elderly or living alone,¹and costly if given by health professionals.²It is therefore not surprising that the search for an oral preparation began soon after cobalamin was isolated and introduced for parenteral use in 1948. Preparations containing oral intrinsic factor were tried, but antibody production caused some patients to become refractory and relapse.³Other studies revealed that a small but constant proportion of an oral dose of cyanocobalamin was absorbed without intrinsic factor, so that by sufficiently increasing the dose, adequate absorption could be attained.⁴,⁵ Promising results from early studies of oral cyanocobalamin therapy led to the use of increasingly larger doses, and several