What is the mechanism of action of ursodiol?

Ursodiol, also known as ursodeoxycholic acid, primarily works through the inhibition of cholesterol secretion into bile. This mechanism is important because it helps to reduce the cholesterol saturation of bile, which can play a significant role in the prevention and dissolution of cholesterol gallstones. By decreasing the amount of cholesterol that is secreted into the bile, ursodiol effectively alters the composition of bile to favor the solubilization of cholesterol and promotes the formation of more soluble forms of bile acids. This not only aids in the dissolution of existing stones but also contributes to overall bile homeostasis.

Additionally, ursodiol has various benefits in conditions such as primary biliary cholangitis and cholestasis, where it helps improve liver function by improving bile flow. Its effectiveness in these contexts further underscores the importance of its action in reducing cholesterol saturation in bile rather than enhancing secretion of bile acids, stimulating bile production, or enhancing lipid absorption.