Maintenance of Elevated Blood Levels of Vitamin B12 in Human Subjects

T HERE is increasing evidence that the ad-ministration of vitamin B12 via the oral route may occassionally give unreliable re-sults in the treatment of Addisonian pernicious anemia and the neurologic disorders frequently associated with this disease. ’ Interest is thus referred back to the parenteral route and with it arises increasing need for a prolonged release form of the vitamin. This need prompted ex-tension of our earlier findings2 which had demonstrated prolonged urinary excretion fol-lowing intramuscular injection of the vitamin in an oil-with-aluminum monostearate depot vehicle. Subsequently, we observed3 that the depot effect of the preparation when tested in dogs was reflected in prolonged elevated blood levels of the vitamin. Administered in depot form, the vitamin remained in the blood twice as long as when it was given in an aqueous mnedium. In this communication evidence from two studies with human subjects is presented to show that vitamin B12 mnay be expected to re-main in the blood three to four times longer when it is givemi as a depot preparation than it does when it is given in water. The elevated levels, nioreover, may persist for three to four weeks. METHODS Two studies were conducted. There were ten healthy subjects in each of two groups in the first Fr umi the Sterling-Winthrop Research Imistitute