<qa>  What is a chronic cholestatic liver disease?Primary biliary cholangitis PBC, formally known as primary biliary cirrhosis is a chronic cholestatic liver disease. Taking advantage of ursodeoxycholic acid UDCA, the outcome of patients with PBC has been improved, comparable to those in general population. However, pruritus, which is often a persisting and annoying symptom, may decrease the quality of life QOL of patients with PBC. Although anti-histamines are administered for this the efficacy is limited, and no drugs which was clearly proved to be effective for suppressing pruritus have been developed worldwide. 