(for veterinary information only)
Most people have heard that one's liver produces a greenish fluid called bile and that this mysterious substance is stored in the gall bladder but beyond this, knowledge of the composition and function of bile simply is not mainstream. Bile is indeed the greenish under-appreciated fluid, produced in the liver and stored in the gall bladder. At the appropriate time in digestion, the gallbladder contracts and bile squirts down the bile duct and into the small intestine. Bile carries with it an assortment of the body's toxins which are thus dumped safely into the gastrointestinal tract and ultimately eliminated in stool. Bile also assists in the absorption of dietary fats, fat-soluble vitamins, and other desirable substances.
(original graphic by marvistavet.com)
Bile consists mostly of cholesterol derivatives called bile acids. There are many types of bile acids, each with different functions. Some are simply lost in the intestine and eliminated in stool as mentioned and some are reabsorbed (i.e., recycled) for reuse by the liver. If more bile acids are required than were reabsorbed, then the liver must make more. If the liver is in failure, reabsorbed bile acids are not captured by the liver for reuse but are instead pass through the liver and into the body's circulation (hence the basis for the bile acids test that has become a popular diagnostic in the evaluation of veterinary liver patients.)
Ursodeoxycholic acid, what we call “ursodiol,” is one of the bile acids produced by the Chinese black bear and it has been used in the treatment of liver disease for centuries. Nowadays, however, it is produced in the laboratory rather and not extracted from bear gall bladders.
There are many benefits to the use of ursodeoxycholic acid in the treatment of liver disease:
Removal of Toxic Bile Acids
Not all bile acids were created equally, meaning that some are more toxic to the liver than others. The bile acids produced by dogs and cats are not as toxic as some of their human counterparts but, in the intestine, even the relatively benign dog and cat bile acids are modified by intestinal bacteria into toxic bile acids. These toxic bile acids are reabsorbed back into the body where they damage the liver if they are allowed to build up. Ursodeoxycholic acid is a non-toxic bile acid. The intestine will preferentially reabsorb ursodeoxycholic acid over more toxic bile acids when the two types are together in the intestine.
Increased bile flow
Small amounts of toxic bile acids get reabsorbed into the liver and are dealt with promptly when the liver is healthy. When the liver is not healthy these bile acids build up and damage the liver further. Ursodeoxycholic acid is what is called a choleretic, which means it improves the flow of bile through the tiny ducts into the gall bladder and improves the flow of bile from the gall bladder into the intestine. In other words, it helps the flow of bile, which in turn facilitates the removal of toxic bile acids (as well as other toxins excreted in bile) from the body.
Ursodeoxycholic acid also appears to have beneficial effects in normalizing immune reactions in the liver and may be useful in the treatment of cirrhosis and chronic active hepatitis.
No serious side effects have turned up in any of the testing of this medication on dogs and cats. The occasional patient experiences some nausea. (Ursodeoxycholic acid is toxic to rabbits, baboons, and rhesus monkeys.)
The use of ursodeoxycholic acid can lower blood cholesterol levels.
There is a possibility that chronic use of ursodeoxycholic acid in cats may deplete the body of the essential amino acid taurine, thus necessitating dietary supplementation with this amino acid. Dogs are able to manufacture their own taurine internally so this issue is not problematic for them.
Ursodeoxycholic acid should not be given at the same time as aluminum containing antacids (such as Amphojel) as these compounds may bind together and impede the action of the ursodeoxycholic acid.
The capsule size is inconveniently large for dosing small animals. A compounding pharmacy is generally needed to produce an appropriately sized medication.
If the common bile duct is obstructed with a gallstone, it's not appropriate to increase bile flow. In such a situation, the use of ursodeoxycholic acid would be contraindicated.
Page last updated: 11/30/2012