rifampicin, opioid-receptor antagonists (naltrexon, naloxone), serotonin-reuptake inhibitors (sertraline), ondansetron, phenobarbital, propofol, lidocaine, dronabinol, butorphanol, internal or external biliary drainage, extracorporeal albumin dialysis, ultraviolet-B phototherapy; NB. Topical menthol containing agents are allowed, as well as bile salt sequestrants (colesevelam, cholestyramin) as long as taken at least 4 hours before or after intake of the study medication. Incidental use of these agents should be noted by patients in the diary, structural use should be noted on the CRF (section co-medication);