DISTURBANCE OF INTESTINAL ABSORPTION FOLLOWING METFORMIN THERAPY (OBSERVATIONS ON MODE OF ACTION OF BIGUANIDES)

Urinary excretion of vitamin B12 and D-xylose, and the levels of blood lipids were determined in 21 patients with clinical or chemical diabetes mellitus and obesity, before and 10 days after metformin treatment. In addition, fat tolerance and fat balance studies were carried out in 7 patients. In a long term study of 9 patients, the Schilling test was repeated 2-3 months after the beginning of the metformin treatment in a) 7 patients with permanent metformin treatment, and b) 2 patients after cessation of initial metformin treatment. The results were as follows: vitamin B12 and D-xylose absorptions were pathologically low after metformin treatment. Blood lipids and body weight were reduced. There was also some indication of disturbed fat absorption, which, however, could not be proved. Based on our results, it is possible that the decrease in blood sugar after treatment with metformin is partly induced by malabsorption of glucose. Thus the concept of Sadow on the effect of metformin on carbohydrate metabolism has to be reëvaluated. The clinical implications of the results, especially with respect to vitamin B12 absorption are discussed. © 1969 Springer-Verlag.