Ursodiol

Overview
Ursodiol, also known as ursodeoxycholic acid and the abbreviation UDCA, is one of the secondary bile acids, which are metabolic byproducts of intestinal bacteria. Primary bile acids are produced by the liver and stored in the gall bladder. When secreted into the colon, primary bile acids can be metabolized into secondary bile acids by intestinal bacteria. Primary and secondary bile acids help the body digest fats. Ursodeoxycholic acid helps regulate cholesterol by reducing the rate at which the intestine absorbs cholesterol molecules while breaking up micelles containing cholesterol. Because of this property, ursodeoxycholic acid is used to treat (cholesterol) gallstones non-surgically.

While some bile acids are known to be colon tumor promoters (eg. deoxycholic acid), others such as ursodeoxycholic acid are chemopreventive, perhaps by inducing cellular differentiation and/or cellular senescence in colon epithelial cells.

Ursodeoxycholic acid has also been shown experimentally to suppress immune response such as immune cell phagocytosis. Increased quantities of systemic (throughout the body, not just in the digestive system) ursodeoxycholic acid can be toxic.

Bile acids are important signaling molecules that help regulate the regrowth of liver tissue, recent research has shown. Ursodeoxycholic acid has been used as an experimental tool in liver regrowth studies. There is a possible link between the immune-repression and liver-regeneration properties of this substance, but clinical studies have yet to confirm these suspicions.

As a pharmaceutical
Ursodeoxycholic acid goes by the trade names Actigall, Ursofalk, Urso, and Urso Forte. At least in Italy, it is marketed under the name Deursil.

Ursodeoxycholic acid can be chemically synthesized and was brought to market by the Montreal-based Axcan Pharma in 1998, which continues to market the drug.

The drug reduces cholesterol absorption and is used to dissolve (cholesterol) gallstones in patients who want an alternative to surgery. The drug is very expensive, however, and if the patient stops taking it, the gallstones recur. For these reasons, it has not supplanted surgical treatment by cholecystectomy.

It is used to treatment primary biliary cirrhosis and other cholestatic diseases. In children it is used in biliary atresia, which is a cause of neonatal jaundice.

Ursodeoxycholic acid reduces elevated liver enzyme levels by facilitating bile flow through the liver and protecting liver cells.

The drug is generally not derived from animals. However, it is believed more than 12,000 bile bears are kept on farms in China, Vietnam and South Korea for the purpose of harvesting ursodeoxycholic acid. Ursodeoxycholic acid is found in large quantities in bear bile.