Introduction
Chronic kidney disease-associated, pruritus, itch
Chronic kidney disease-associated pruritus (CKD-aP) is a very frequent and frustrating problem for both patients and clinicians. The incidence of CKD-aP varied between 40.0% and 72.5% of patients undergoing hemodialysis in the literature [It has been shown that an imbalance of endogenous opioid system may be one contributor to the itch of CKD-aP, and the μ-opioid system is itch-inducing, whereas the κ-opioid system is itch-suppressive [A limitation of the above clinical trials was that the registered patient populations had the same background. In some ways, there is ethnic difference between Chinese and Japanese populations, which may alter the drug’s safety, efficacy, or dose response. Therefore, it is important to know whether the result from the previous phase III trial conducted in Japan [