A 56-year-old woman complains of itching skin of her torso, constant nausea, constipation, sensation of heaviness and pain in the right subcostal area, extreme general fatigue. The patient suffers from biliary cirrhosis. The skin is pale icteric. The abdomen is soft, the liver protrudes 2,0 cm from under the margin of the right costal arch, sensitive on palpation. Biochemical investigation: total bilirubin - 142,0 mcmol/l, conjugated bilirubin - 139,0 mcmol/l, alanine aminotransferase -0,98 mmol/hour·l, aspartate aminotransferase - 0,82 mmol/hour·l alkaline phosphatase - 8,7 mmol/hour·l. What drug should be prescribed in the first place?