Vitamin B12 Replacement Therapy After Gastrectomy

Mechanisms of vitamin B12 absorption has been known widely. The Mechanisms are classified into two mechanisms. One is passive, occurring equally through buccal, duodenal, and ileal mucosa; it is rapid but extremely inefficient, with <1% of an oral dose being absorbed by this process. The other one is active; it occurs through the ileum and is efficient for small oral dose of vitamin B12, and it is mediated be substance named gastric intrinsic factor. Intrinsic factor is produced in the gastric parietal cells of the fundus and body of the stomach. Between 0.5-5μg of cobalamin excreted with the bile each day. This binds to intrinsic factor, and a major portion of biliary cobalamin normally is reabsorbed together with cobalamin derived from sloughed intestinal cells. Because of the loss of these effective absorption and reabsorption mechanism, vitamin B12 deficiency develops more rapidly after gastrectomy [1,2].