The bile salt export pump BSEP is critically involved in secretion of bile salts into bile. Its function can be disturbed or abolished by inherited mutations. This will lead to progressive intrahepatic cholestais and severe liver disease. In addition to mutations, Bsep can be inhibited by acquired factors such as for example xenobiotics or drugs, aberrant bile salt metabolites or pregnancy. This inhibition will lead to acquired cholestasis. Some drugs are now known to be competitive inhibitors of Bsep. In addition, a polymorphism in the gene coding for Bsep has been identified as a potential susceptibility factor for acquired cholestasis [PMID: 20028269].