Ursodeoxycholic Acid (UDCA), also known as ursodiol, is a naturally occurring bile acid. Its synthetic form is used as a medication for various digestive and liver conditions. UDCA influences bile composition, a liver-produced fluid essential for fat digestion, and helps regulate cholesterol handling.
How UDCA Works in the Body
UDCA works primarily by altering the composition of the bile acid pool. It is a hydrophilic, or water-loving, bile acid, which helps to displace more hydrophobic, or water-fearing, bile acids that can be harmful to liver cells. By increasing the proportion of UDCA in bile, it reduces the concentration of these potentially toxic bile acids.
This shift in bile composition also helps dissolve cholesterol gallstones. UDCA reduces cholesterol secretion from the liver into bile and inhibits intestinal cholesterol absorption, decreasing bile’s cholesterol saturation. This makes it less likely for stones to form and can break down existing ones.
UDCA also protects liver cells, known as hepatocytes, and bile duct cells, called cholangiocytes, from damage by toxic bile acids. It stabilizes cell membranes and stimulates bicarbonate secretion into bile, creating a protective alkaline barrier. Additionally, UDCA has anti-inflammatory and immunomodulatory effects, influencing immune responses.
Primary Medical Uses of UDCA
UDCA is a recognized treatment for several medical conditions affecting the liver and gallbladder. One established use is dissolving cholesterol gallstones. While surgery is common for symptomatic gallstones, UDCA offers a non-invasive alternative for smaller, non-calcified stones in patients who prefer not to undergo surgery or are not candidates. Treatment may continue for up to two years.
The medication is also widely used for Primary Biliary Cholangitis (PBC), a chronic liver disease where bile ducts within the liver are progressively damaged. UDCA is the only FDA-approved medication for PBC. It can significantly delay liver damage progression and improve liver function, especially in early stages. It is considered the treatment of choice for PBC, with long-term use often recommended.
UDCA also shows potential in managing other cholestatic liver diseases, where bile flow from the liver is impaired. It has been explored for conditions such as intrahepatic cholestasis of pregnancy (ICP). While UDCA can improve liver tests and symptoms like itching in ICP, its effect on birth outcomes requires further research. UDCA has also been investigated for cystic fibrosis-associated hepatobiliary disorder and for preventing gallstones in individuals undergoing rapid weight loss, such as after bariatric surgery.
Understanding UDCA Dosing and Administration
The appropriate dosage of UDCA varies considerably depending on the specific condition and individual patient factors. For gallstone dissolution, a typical dosage is 8 to 10 mg/kg per day, often divided into two to four doses. For Primary Biliary Cholangitis (PBC), a common dosage range is 13-15 mg/kg per day, usually administered in two to four divided doses. Some studies suggest an optimum dose for PBC may be around 900 mg per day.
UDCA is available in various forms, including capsules, tablets, and liquid medicine. It is recommended to take UDCA with food or a snack to enhance absorption and facilitate bile secretion. Consistent timing for doses each day helps ensure effectiveness. A healthcare professional must determine the exact dosage and administration schedule, considering the patient’s specific condition, weight, and overall health.
Potential Side Effects and Important Interactions
UDCA is well-tolerated, but some individuals may experience side effects. Common gastrointestinal side effects include diarrhea, constipation, nausea, vomiting, and dyspepsia. Less common side effects include recurrent right upper abdominal pain, and rarely, calcification of gallstones or decompensation of liver cirrhosis. Headache, dizziness, and back pain are also infrequently reported.
It is important to be aware of potential drug interactions when taking UDCA. Certain medications can reduce the absorption and effectiveness of UDCA, such as bile acid-binding resins and antacids containing aluminum. It is advised to take UDCA at a different time than these other medications. Conversely, UDCA may affect the absorption or serum concentration of other drugs, for example, increasing ciclosporin levels or reducing ciprofloxacin absorption. The effectiveness of UDCA can be reduced by estrogen hormones, oral contraceptives, and certain cholesterol-lowering agents, as these can increase hepatic cholesterol secretion.
UDCA is contraindicated in individuals with certain conditions, including acute inflammation of the gallbladder or biliary tract, complete biliary obstruction (of either extrahepatic or widespread intrahepatic origin), frequent episodes of biliary colic, or radio-opaque calcified gallstones. It should also be avoided in patients with impaired gallbladder contractility or those with active duodenal and gastric ulcers. Individuals with severe liver impairment or certain intestinal conditions that interfere with bile acid recirculation should also not take UDCA.