Ursodiol

Ursodiol, also known as ursodeoxycholic acid and the abbreviation UDCA, is one of the secondary bile acids, which are metabolic byproducts of intestinal bacteria.

Endogenous effects
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 (e.g. deoxycholic acid), others such as ursodeoxycholic acid are thought to be chemopreventive, perhaps by inducing cellular differentiation and/or cellular senescence in colon epithelial cells.

It is believed to inhibit apoptosis.

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

As a pharmaceutical
Ursodeoxycholic acid goes by the trade names Actigall, Ursosan, Ursofalk, Urso, and Urso Forte. In Italy and Switzerland, 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 tend to recur if the condition that gave rise to their formation does not change. For these reasons, it has not supplanted surgical treatment by cholecystectomy.

It is the only FDA approved drug to treat primary biliary cirrhosis.

A Cochrane review to evaluate if ursodeoxycholic acid has any beneficial effect in primary biliary cirrhosis patients included 16 randomized clinical trials with a total of 1447 patients. The primary outcome measures were mortality and mortality or liver transplantation. Although treatment with ursodeoxycholic acid showed a reduction in liver biochemistry, jaundice, and ascites, it did not decrease mortality or liver transplantation.

In children, its use is not licensed, as its safety and effectiveness are not established. In double the recommended daily dose ursodeoxycholic acid reduces elevated liver enzyme levels in patients with primary sclerosing cholangitis, but its use was associated with an increased risk of serious adverse events (the development of cirrhosis, varices, death or liver transplantation) in patients who received ursodeoxycholic acid compared with those who received placebo). After adjustment for baseline stratification characteristics, the risk was 2.1 times greater for death,transplantation, or minimal listing criteria in patients on ursodeoxycholic acid than for those on placebo (P = 0.038). Serious adverse events, were more common in the ursodeoxycholic acid group than the placebo group (63% versus 37% [P < 0.01])).

Production
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.