At the end of treatment, we found a significant expansion of the total serum bile acid pool and marked UDCA and LCA enrichment in the UDCA-treated patients versus the placebo group when pretreatment levels were compared. Additionally, we found that the increases in serum bile acid levels seemed to correlate with worse outcomes because the subset of patients that reached the clinical endpoints of disease progression during UDCA therapy tended to have higher bile acid levels. The proposed UDCA mechanisms of action in hepatobiliary disorders include expansion of

the hydrophilic bile acid pool and hypercholeresis.16 Early studies in gallstone patients showed that UDCA administration this website could modify the composition of circulating bile acids and lead to UDCA predominance.17, 18 Multiple subsequent studies, most of them in patients with primary biliary cirrhosis, Selleck GSK1120212 have verified this modification and have generally revealed an overall expansion

of the total bile acid pool.8, 9, 13, 14, 19-22 Rost et al.13 in a study of biliary bile acid composition in patients with PSC specifically indicated that UDCA enrichment was augmented (43.1% ± 0.3% to 58.6% ± 2.3% of total bile acids) parallel to an escalating dose of UDCA (10-13 to 22-25 mg/kg/day) and reached a plateau at the highest dose. This enrichment did not further increase beyond that dose.13 In our study, the mean changes in UDCA and total bile acid levels post-treatment were significantly higher in the UDCA group compared to the placebo group (P < 0.0001). The mean posttreatment UDCA percentage in the bile acid pool was 74%, far higher than that ever reported in any other study, and

this implies that enrichment is increased proportionally to the dose. Nonetheless, this high enrichment did not correspond to a better outcome. Therefore, further investigation of biliary enrichment has to be performed, especially with respect to clinical outcome. Changes in the levels of other bile acids under UDCA treatment have been generally considered to follow an inverse relationship between the increase in UDCA levels also and the decrease in CA, CDCA, DCA, and LCA levels. Results, however, are not homogeneous, and the changes are not significant in the majority of cases.13, 21, 22 In PSC patients, one study has suggested that LCA levels are not increased, even after high-dose UDCA treatment.13 Nonetheless, the antibiotics administrated in that study during the endoscopic retrograde cholangiography procedure used to obtain samples for bile acid analysis might have interfered with the results. Nonsignificant changes between the two treatment groups for CDCA, CA, and DCA levels were observed in our study after treatment. Levels of CDCA, CA, and DCA were slightly decreased in the placebo group, whereas in the UDCA group, CA showed a tendency to decrease, and DCA and CDCA were slightly increased.