The efficacy and safety of TRK-820 are to be evaluated in the treatment of intractable pruritus in patients with Chronic Liver Disease by administering 2.5, 5 and 10 microg of this drug or placebo for 28 days in four groups with a design of randomized, double-blind, parallel-group comparison. In addition, the plasma concentrations of TRK-820 and its primary metabolites are to be determined.

Inclusion Criteria:

• Chronic Liver Disease is present; and the patient's general condition is judged by the physician to be stable with no prospect of an abrupt change in pathophysiology.
• It can be confirmed by either of the following that treatment of pruritus with antihistamines or antiallergics has not been adequately effective in such patients:

Exclusion Criteria:

• Malignant tumors
• Depression, integration dysfunction syndrome (schizophrenia), or dementia
• Hepatic encephalopathy, or hepatic cirrhosis in which ascites or esophageal or gastric aneurysm cannot be controlled
• Alcoholic liver disease
• Atopic dermatitis, chronic urticaria, or other skin disease producing generalized pruritus that is judged by the physician to affect the assessment of pruritus associated with Chronic Liver Disease in this study
• Allergy to opioid drugs
• Drug dependence or alcohol dependence
• Chronic renal failure