In a randomized, double-blind study of nalfurafine hydrochloride, the KOR agonist nalfurafine hydrochloride (2.5 or 5 μg daily) was effective without significant side effects in the treatment of intractable pruritus in patients with chronic liver disease [223]; however, endogenous opioid levels and MOR/KOR ligands did not differ between the levels of pruritus and nonpruritic patients with chronic liver disease and did not correlate with itch intensity [224]. Here, OPRM1 is linked to Pruritus.