Several drugs, including certain chemotherapeutic agents (methotrexate), antimalarials (pyrimethamine), diuretics (triamterene), protozoacides (pentamidine isethionate), antibacterials (trimethoprim), anticonvulsants (diphenylhydantoin sodium), sedatives (barbiturates), oral contraceptives, antituberculous agents (cycloserine, para-aminosalicylic acid), and colchicine (for gout), may produce intestinal malabsorption of vitamin B-12 or of folic acid, or both (1). The latest culprit to be added to the ranks of such drugs is metformin (2), a member of the biguanide group of oral hypoglycemic agents used to treat obese, mild-diabetes patients, in whom they are alleged to favor weight loss (3).
Any drug capable of producing intestinal malabsorption may potentially produce malabsorption of vitamin