Drug interactions related to drug absorption. The anion exchange resins, colestyramine,92–94 colestimide95 and colestipol,94 bind UDCA in the gut and thereby interfere with the absorption of UDCA. Aluminium hydroxide and smectite are notable for their propensity to form complexes with UDCA which are not absorbed.94 Therefore, it is recommended that these drugs are administered with an adequate interval to UDCA.96 The absorption of vitamin E improved in a patient with cystic fibrosis and pancreatic insufficiency after administration of UDCA. More effective intestinal fat absorption after UDCA-induced stimulation of bile acid secretion was proposed to be responsible for this effect.97