During normal digestion, bile acids are secreted via the bile from the liver and gall bladder into the intestines.
Bile acids emulsify the fat and lipid materials present in food, thus facilitating absorption.
A major portion of the bile acids secreted is reabsorbed from the intestines and returned via the portal circulation to the liver , thus completing the enterohepatic cycle. Only very small amounts of bile acids are found in normal serum. Colestipol hydrochloride binds bile acids in the intestine forming a complex that is excreted in the feces. This nonsystemic action results in a partial removal of the bile acids from the enterohepatic circulation, preventing their reabsorption. Since colestipol hydrochloride is an anion exchange resin, the chloride anions of the resin can be replaced by other anions, usually those with a greater affinity for the resin than the chloride ion.