Ursodiol

Introduction Overview

Generic Name

ursodiol

Brand Name

Reltone, Actigall, Urso, Urso DS, Urso Forte

Dosage Form

oral capsule (200 mg; 300 mg; 400 mg), oral tablet (250 mg; 500 mg)

Drug Class

Gallstone solubilizing agents

Pharmacokinetics

Absorption:
Ursodiol is administered orally and is well absorbed in the gastrointestinal tract. Its absorption occurs primarily in the small intestine, where bile salts normally facilitate the emulsification and uptake of lipophilic substances. However, the bioavailability of ursodiol can be affected by concomitant intake of other drugs such as bile acid sequestrants and antacids containing aluminum, which may interfere with its absorption by binding to ursodiol and reducing its availability. The absorption process is also influenced by hepatic function and enterohepatic circulation, which plays a crucial role in maintaining plasma levels of ursodiol and its metabolites.

Distribution:
Following absorption, ursodiol is extensively distributed to tissues, particularly accumulating in the liver, the primary site of action, and the biliary system. It undergoes enterohepatic recirculation, cycling between the liver and intestines, which helps maintain therapeutic concentrations over time. Plasma protein binding is variable, mainly to albumin, and this binding influences the drug's distribution volume and clearance. The volume of distribution reflects extensive tissue uptake, mostly localized within the hepatobiliary system to exert its therapeutic effects.

Metabolism:
Ursodiol undergoes hepatic metabolism primarily through conjugation with glycine or taurine, forming ursodeoxycholyl glycine and taurine conjugates. These conjugates increase its solubility in the bile. The metabolism is facilitated by the liver's enzymatic systems and is part of its mechanism to reduce cholesterol saturation in bile and modify bile acid composition. Metabolic pathways are influenced by liver function; impaired hepatic metabolism can alter ursodiol pharmacokinetics and necessitate dosage adjustments.

Elimination:
Elimination occurs predominantly via the biliary excretion route into the feces following enterohepatic circulation. Only minimal amounts of ursodiol and its conjugates are excreted in urine. The enterohepatic recycling prolongs the half-life, which is approximately 3.5 to 5.8 days, contributing to sustained therapeutic plasma concentrations. Because the drug is excreted in bile, hepatic impairment may reduce clearance, increasing systemic exposure and potential toxicity. Regular monitoring of liver function is essential during prolonged therapy.

Dosage Forms

Available Dosage Forms:
Ursodiol is available as oral capsules with doses of 200 mg, 300 mg, and 400 mg, and as oral tablets in 250 mg and 500 mg strengths. The capsules and tablets are formulated for oral administration and intended for chronic management requiring precise dosing adjustments.

Dosages for Adults and Adolescents:
For primary biliary cirrhosis (PBC), adult patients are typically dosed with ursodiol tablets at 13 to 15 mg/kg per day, administered in two to four divided doses taken with food. The tablet form may be scored for dose adjustment, with broken pieces swallowed whole to avoid a bitter taste.
For gallbladder disease, oral capsules are prescribed at 8 to 10 mg/kg per day divided into two to three doses for gallstone dissolution. For gallstone prevention, a fixed dose of 300 mg twice daily (600 mg maximum daily dose) is recommended. Treatment duration may extend several months, with periodic ultrasound monitoring.

Specific Patient Populations:
Use in pediatric patients younger than 18 years is not approved due to lack of sufficient safety and efficacy data. In patients with hepatic dysfunction, dosage adjustments and careful monitoring are necessary given altered metabolism and clearance. Ursodiol should be used cautiously in patients with biliary obstruction or hypersensitivity. Pregnant and breastfeeding women should use the medication only under strict medical supervision, balancing potential benefits and risks.

Clinical Guidelines:
Treatment for gallstones is typically prolonged; ultrasound evaluations every 6 months during the first year are recommended to assess gallstone dissolution. If partial dissolution is not evident after 12 months, discontinuation or alternative therapies should be considered. In PBC, long-term treatment aims to improve liver biochemical tests and delay progression of liver damage.

Mechanism Of Action

Ursodiol, chemically identified as ursodeoxycholic acid, is a hydrophilic bile acid that exerts its therapeutic effect primarily by altering the composition and flow of bile. Its principal mechanism involves replacing more hydrophobic and potentially hepatotoxic endogenous bile acids in the bile acid pool, thereby reducing bile acid-induced epithelial cell injury in the liver and biliary epithelium. This substitution leads to cytoprotection and improved cholestasis.

At the molecular level, ursodiol reduces cholesterol saturation in bile by decreasing intestinal absorption and hepatic secretion of cholesterol while increasing bile acid secretion. By decreasing cholesterol concentration in bile, it promotes the solubilization and gradual dissolution of cholesterol gallstones that are non-calcified and radiolucent. This modification of bile composition favors the dissolution process, preventing further stone formation and facilitating the reduction of existing stones.

Cellular pathways affected by ursodiol include the inhibition of apoptosis in hepatocytes and cholangiocytes, possibly through stabilization of mitochondrial membranes and reduction of oxidative stress. These effects contribute to hepatoprotective properties, particularly relevant in primary biliary cirrhosis, where progressive autoimmune destruction of bile ducts occurs. Additionally, ursodiol stimulates bile flow (choleretic effect), easing cholestasis and restoring normal bile secretion dynamics.

Clinical studies have demonstrated that ursodiol improves liver biochemistry and delays disease progression in patients with primary biliary cirrhosis. Compared with other bile acids and cholesterol-lowering agents, ursodiol's unique properties as a natural bile acid provide a favorable safety profile and targeted therapeutic benefit. Research into combination therapies continues, exploring synergistic effects with other agents for enhanced clinical outcomes.

Pharmacological Actions

Reduces cholesterol saturation in bile, facilitating dissolution of cholesterol gallstones.
Replaces endogenous hydrophobic bile acids, reducing hepatocyte and biliary epithelial injury.
Exerts cytoprotective effects on liver cells by stabilizing mitochondrial membranes and reducing apoptosis.
Improves bile flow and reduces cholestasis via choleretic activity.
Modulates immune-mediated bile duct injury in primary biliary cirrhosis through anti-inflammatory effects.
Decreases intestinal cholesterol absorption and hepatic cholesterol secretion.
Participates in enterohepatic circulation, maintaining bile acid homeostasis.
Promotes gradual dissolution of radiolucent, noncalcified gallstones less than 20 mm in diameter.
Has a favorable safety profile with minimal systemic toxicity due to extensive hepatic clearance.
Facilitates improvement of liver biochemical markers in cholestatic liver diseases.

Therapeutic Or Clinical Uses

Dissolution of small, noncalcified cholesterol gallstones in patients unsuitable for surgery.
Prevention of gallstone formation in obese patients undergoing rapid weight loss.
Treatment of primary biliary cirrhosis (PBC) to delay progression of liver disease.
Management of cholestatic liver diseases with impaired bile flow.
Adjunctive therapy to improve liver function tests in autoimmune biliary conditions.
Alternative to surgery in patients with increased perioperative risk due to age or comorbidities.
Reduction of symptoms associated with gallbladder disease refractory to other treatments.
Utilized in long-term management post gallstone dissolution to reduce recurrence risk.
Potential use in combination regimens with other bile acid analogs or liver-protecting agents.
Supportive treatment to improve quality of life in chronic cholestatic conditions.

Side Or Adverse Effects

Gastrointestinal disturbances including upset stomach, nausea, vomiting, diarrhea, and constipation.
Signs of allergic reaction such as hives, facial swelling, difficulty breathing, and throat tightening.
Liver-related adverse effects manifesting as nausea, upper abdominal pain, jaundice, dark urine, and clay-colored stools indicating possible hepatotoxicity.
Pain or burning sensation during urination.
Potential development of infections presenting with fever, chills, sore throat, mouth or skin sores.
Respiratory symptoms including cough and sore throat.
Uncommon side effects such as hair loss (alopecia) and back pain.
Fatigue and weakness especially in the context of progressive liver disease.
Rare reports of hypersensitivity reactions requiring immediate medical attention.
Elevated liver enzymes requiring periodic monitoring during prolonged therapy.

Precautions

Do not use if allergic to ursodiol or components of the formulation.
Avoid use in patients with obstruction of liver or gallbladder bile ducts.
Monitor liver function tests regularly during treatment, especially with prolonged use.
Use cautiously in patients with pre-existing liver or biliary diseases other than those indicated.
Pregnant and breastfeeding women should use ursodiol only if clearly needed and prescribed by a physician.
Not approved for use in children under 18 years of age.
Careful dose adjustment is necessary in patients with rapidly changing body weight.
Advise women of childbearing potential to inform healthcare provider if pregnant or planning pregnancy.
Avoid abrupt discontinuation; follow medical advice for tapering or stopping therapy.
Be aware of potential drug interactions that may affect ursodiol’s absorption or therapeutic efficacy.

Warnings

Use ursodiol strictly as directed by a healthcare professional.
Report immediately any signs of allergic reaction including swelling, hives, or respiratory distress.
Patients should notify their doctor if symptoms worsen or if there is no improvement after an adequate treatment period.
Avoid concomitant use of agents that interfere with bile acid absorption without medical supervision.
The medication is not a substitute for surgical intervention in patients eligible for cholecystectomy.
Long-term safety beyond 24 months for gallstone dissolution has not been firmly established.
Use with caution in patients with rapid weight gain or signs of fluid retention.
Do not use if there is complete obstruction of the biliary tract.
Inform healthcare provider of all medications being taken to avoid interactions.
Regular monitoring including liver ultrasounds and biochemical tests is recommended for ongoing assessment.

Contraindication

Known hypersensitivity or allergy to ursodiol or any formulation component.
Obstruction of bile ducts in the liver or gallbladder preventing bile flow.
Presence of calcified or radiopaque gallstones which are resistant to dissolution.
Use in pediatric patients under 18 years due to insufficient safety data.
Patients with acute biliary pancreatitis associated with gallstones.
Severe hepatic impairment where drug metabolism and elimination are compromised.
Pregnancy or breastfeeding unless benefits outweigh potential risks and under strict medical supervision.
Patients with complete biliary obstruction or cholestasis of other etiologies.
Concomitant use with drugs that severely impair bile acid metabolism without medical advice.
Patients with a history of intolerance or adverse reactions to bile acid therapy.

Drug Interactions

Reduced absorption of ursodiol when administered with antacids containing aluminum.
Bile acid sequestrants such as cholestyramine and colestipol significantly decrease ursodiol absorption by binding bile acids.
Interaction with oral contraceptives may alter bile acid metabolism and require monitoring.
Estrogens and clofibrate can influence bile composition and may affect ursodiol efficacy.
Potential alterations in ursodiol plasma levels with concomitant use of other hepatically metabolized drugs.
Herbal supplements and over-the-counter medications may interfere with ursodiol action; consultation recommended.
Drugs affecting hepatic enzyme activity might modify ursodiol pharmacokinetics.
Co-administration with agents that modify gastrointestinal motility can impact ursodiol absorption.
Monitoring is required when combined with other gallstone therapy agents due to potential additive effects.
No significant interaction with warfarin or other common anticoagulants reported.

Preparations Of The Drug

Ursodiol oral capsules in strengths of 200 mg, 300 mg, and 400 mg.
Ursodiol oral tablets available as 250 mg and 500 mg scored tablets for dose flexibility.
Formulations designed for oral administration with variable dosing for different indications.
Scored tablets allow for precise dose adjustments by splitting to half tablets.
Capsule formulations generally intended for gallstone dissolution and prevention.
Tablet forms typically used for primary biliary cirrhosis treatment.
All formulations should be stored at room temperature away from moisture and heat.
Broken tablets should be used within 28 days and swallowed whole to avoid bitter taste.
Available under multiple brand names including Actigall, Urso, Urso Forte, and Reltone.
Prescription-only formulations requiring physician oversight for proper dosing and monitoring.