Hematologic Responses and Concenrtation of Vitamin B₁₂ in Serum and Urine following Oral Administration of Vitamin B₁₂ without Intrinsic Factor

Vitamin B₁₂ in doses of 500 to 3000 µg. was given by mouth or by rectum to patients with megaloblastic anemia due to B₁₂ deficiency and to normal subjects. Its absorption was studied by following the hematologic response and/or the changes in serum and urinary B₁₂ concentrations by microbiologic assay with Euglena gracilis var. bacillaris.

After oral doses of 1000 to 3000 µg. of B₁₂ there was a definite but variable hematologic response in the thirty-five patients. The serum B₁₂ concentrations, measured in eighteen of these patients, increased in the first twenty-four hours after the dose. The urinary excretion of B₁₂ increased in fifteen out of sixteen patients, but the average amount excreted was only one quarter of that excreted after intramuscular injections producing comparable hematologic responses. The lower urinary excretion after the oral doses was associated with a lower total and uncombined B₁₂ concentration in the serum. In the majority of patients serum B₁₂ concentrations and urinary B₁₂ excretion reached a maximum in the first six hours after the dose.

After oral doses of 3000 µg. there was a rise in serum and urinary B₁₂ in three out of four normal subjects.

After doses of 500 µg., there was an increase in the serum B₁₂ concentrations of two normal subjects and of one out of two patients with megaloblastic anemia, but there was no change in urinary B₁₂ excretion.

After rectal doses of 1000 or 3000 µg. there was evidence of absorption of the vitamin in seven out of eight patients with pernicious anemia.