Inclusion Criteria:
At the time of signing informed consent:
* Aged 18-85 years (inclusive), regardless of gender.
* Chronic renal failure patients on regular peritoneal dialysis for ≥3 months, with no anticipated major treatment changes or rapid disease progression during the trial.
* Able to understand and comply with study procedures, voluntarily participate, and provide written informed consent.
At formal enrollment:
* During the baseline period, ≥5 days with both morning and evening VAS scores recorded, and the average of the higher VAS values (morning/evening) ≥50 mm.
* During the baseline period, ≥5 days with Xie-Kawashima itching severity assessed both morning and evening, including ≥2 days where the maximum itching score (morning/evening) was ≥3 (moderate).
Exclusion Criteria:
* Poor dialysis compliance, deemed by the investigator to affect efficacy/safety assessments.
* Poor dialysis compliance, deemed by the investigator to affect efficacy/safety assessments.
* Peritoneal dialysis regimen adjusted within 2 weeks prior to screening.
* Currently on or planning hemodialysis within 2 months.
* Planned kidney transplant or elective surgery during the study.
* Peritonitis within 4 weeks prior to screening, unable to continue peritoneal dialysis.
* ALT, AST, GGT, or total bilirubin \>2× upper limit of normal (ULN) during screening.
* Pruritus not caused by chronic kidney disease (e.g., allergic, physical, infectious skin diseases, cholestatic liver disease).
* Severe cardiovascular disease (NYHA Class III/IV, acute MI, unstable angina, large pericardial effusion, severe arrhythmia, or ECG abnormalities deemed unsafe for participation).
* Active malignancy within 12 months prior to screening, or recent radiotherapy/chemotherapy/targeted/immunotherapy.
* Uncontrolled or drug-treated fungal/bacterial/viral infections (e.g., active TB, HIV).
* Uncontrolled hypertension (SBP ≥180 mmHg or DBP ≥110 mmHg).
* Current systemic corticosteroids/immunosuppressants (topical excluded).
* Psychiatric or cognitive disorders.
* Initiated/adjusted restricted medications (antihistamines, systemic/local corticosteroids \[excluding ear/eye\], calcineurin inhibitors, gabapentin, pregabalin) within 7 days prior to screening, or anticipated changes during the study.
* Initiated/adjusted medications affecting pruritus assessment (antipsychotics, hypnotics, SSRIs, anxiolytics, TCAs) within 2 weeks prior to screening, or anticipated changes during the study.
* Opioid agonists/antagonists used within 2 weeks prior to screening.
* Phototherapy for pruritus within 1 month prior to screening.
* History of drug abuse, dependence, or alcoholism within 12 months prior to screening.
* Allergy to opioids or trial drug excipients.
* Participation in another clinical trial with investigational drugs/devices within 28 days prior to screening, or residual investigational drug within 5 half-lives.
* Pregnant, breastfeeding, positive pregnancy test, or unwilling to use contraception during the study.
* Other conditions deemed unsuitable by the investigator.
