This is a multisite study to evaluate the efficacy, safety and plasma concentration of Nalfurafine Hydrochloride orally disintegrating tablet in the treatment of refractory pruritus in maintenance hemodialysis patients, and to bridge the efficacy data from Japan

This clinical trial is a bridging study. when selecting the subjects, the most appropriate pruritus medication for the subjects was used first.Then, subjects with "existing treatment-resistant" pruritus will continue to receive basic pruritus treatment if the corresponding treatment is not sufficiently effective, and the experimental drug or placebo will be added to this treatment to evaluate the effectiveness.

Inclusion Criteria:

1. Chronic renal failure patients who have been on stable dialysis for 3 months or more, receive regular hemodialysis 3 times a week, and expect no significant treatment changes or dramatic changes in their condition during the clinical trial;
2. In the 1 year prior to signing the informed consent, patients who were treated with the following drugs A and/or B: (A) Systematic treatment (oral, injection, etc.) of "prescribed drugs for pruritus" (including antihistamines or antiallergic drugs) for more than 2 weeks consecutively; (B). Use of " prescribed drugs for pruritus" (ointments, etc.) or topical treatment of moisturizers prescribed by physicians;
3. Patients who had received treatment in inclusion criteria (2) but did not respond;
4. When signing the informed consent, the patient is older than 18 years old (including 18 years old), regardless of gender;
5. During the observation period before administration (D8-14), the number of days for which the VAS values were measured at the time of getting up and going to bed should not be less than 5 days, and the average value of the larger VAS values in the morning and evening measurements should not be less than 50 mm;
6. During the observation period before administration (D8-14), The number of days in which the larger VAS value measured in the morning and evening measurements (if there was a missing time in getting up or going to bed, the value which has been measured was selected) is not less than 20 mm, was not less than 5 days;
7. During the observation period before administration (D8-14), the number of days in which the pruritus severity of Hsie-Kawashima's was evaluated at the time of getting up and at the time of going to bed was not less than 5 days, in which the maximum of the pruritus score was not less than 3 (moderate) in the morning and evening measurements was more than half.

Exclusion Criteria:

1. Malignant tumor patients;
2. Patients with mental illness or mental retardation who cannot correctly understand the VAS score and describe their feelings;
3. Patients with alanine aminotransferase (ALT), aspartate aminotransferase (AST) or glutamine transferase (GGT) or total bilirubin higher than twice the upper limit of normal value (ULN) at the screening stage;
4. Patients currently suffering from atopic dermatitis or chronic urticaria;
5. Patients allergic to opioids;
6. Patients with drug or alcohol dependence;
7. Patients who had received light therapy for pruritus within 1 month prior to signing the informed consent;
8. Patients who have participated in a previous clinical study of Nalfurafine Hydrochloride and have taken Nalfurafine Hydrochloride, or who have participated in this clinical study and have been officially enrolled;
9. Participated in other clinical studies (including research drugs and medical devices) within 1 month before signing the informed consent;
10. Pregnant women, lactating women, women who have a positive pregnancy test or who do not agree to use contraception during the study period;
11. Patients who, as determined by the investigator, could not have their VAS score recorded by themselves for any reason;
12. Patients whose comorbidities or previous medical history, as determined by the investigator, would affect the evaluation of this clinical study;
13. After testing, human immunodeficiency virus antibody positive;
14. Other patients judged by the investigator to be unsuitable for participation in this clinical study.