In five patients with radiolucent gallstones, the effect of ursodeoxycholic acid (Urso) in doses of 250, 500, 750, 1,000, and 1,250 mg per day on biliary lipid and bile acid composition was studied. Biliary cholesterol decreased from 8.8 ± 0.8 mole% to 4.4 ± 0.2 mole% at 500 mg Urso per day (7.1 mg per kg) and to 4.2 ± 0.3 mole% at 750 mg Urso per day (10.7 mg per kg). Administration of 1,000 or 1,250 mg Urso per day produced no further decrease of biliary cholesterol. The biliary content of phospholipids and total bile acids remained unchanged.

During Urso treatment, the relative amounts of glyco-Urso and tauro-Urso in bile increased. Glyco-Urso reached a plateau at 49.1 ± 2.1% of total bile acids during treatment with 1,000 mg Urso per day, and tauro-Urso increased up to 4.3 ± 1.5% of total bile acids at 250 mg Urso per day. Simultaneously cholic acid, chenodeoxycholic acid, deoxycholic acid, and lithocholic acid decreased.

The data indicate that Urso treatment reduces biliary cholesterol efficiently already at a dose of 500 mg per day; biliary bile acid composition changes up to 1,000 mg Urso per day. Doses greater than 1,000 mg per day produced no additional alterations in bile composition.