ORAL TREATMENT OF PERNICIOUS ANEMIA WITH HIGH DOSES OF VITAMIN B12 WITHOUT INTRINSIC FACTOR

Abstract The concluded results of an experimental study are reported, confirming that the absorption of vitamin B12 takes place in two ways: 1. through the mediation of intrinsic factor; 2. without mediation of intrinsic factor. The former mechanism allows a B12 absorption in normally IF‐sensitive cases of pernicious anemia and in normal persons with an upper limit of about 2 μg. The latter mechanism allows an absorption of vitamin B12 which is roughly proportional to the oral dose administered, and amounts to about 1.2% of the dose, within a very wide dose range. Thus, it is possible to increase the uptake to any desired level. This direct uptake was found to be of the same magnitude, irrespective of whether the patient had a normal absorption, was suffering from pernicious anemia with or without resistance to intrinsic factor preparations, or had some other form of disturbed B12 absorption (idiopathic malabsorption, postoperative state after extensive gastric or intestinal resections, or ileitis). The result of a long‐term clinical trial is also reported, in which a daily oral dose of 500–1000 μg of vitamin B12 without intrinsic factor was given to patients with pernicious anemia and other types of vitamin B12 deficiency. The material comprised 64 patients followed for up to more than 5 years. After the remission period very few serum B12 determinations showed borderline or subnormal values, and low levels were never of long duration. At the conclusion of the study the serum B12 values were well within the normal range in all cases. Also the individual mean values of the B12 determinations, made during the observation period from the second month of treatment, were normal in all cases. No neurological complications were observed. The blood values were normal in all but a few cases, in which concurrent diseases were present (malignancy, chronic infections, iron deficiency states). Experimental evidence obtained indicates that oral treatment with 500 μg of B12 daily has also resulted in replenishment of the B12 depots. The treatment with high oral doses of vitamin B12 thus constitutes a convenient and completely reliable maintenance therapy in pernicious anemia and other states of B12 deficiency, and is a fully acceptable alternative to the conventional method of vitamin B12 injections. This type of therapy (1000 μg B12 daily) was introduced into Sweden in 1964 and is now extensively used.