Thus, opioids may play a role in both peripheral as well as central modulation of pruritus in uremic pruritus and other pruritic diseases such as AD, in which decrease of kappa-opioid receptors (KOR) but not of μ-opioid receptors (MOR) have been found in the skin, resulting in a misbalance of the MOR over KOR system (18). This evidence concerns the gene OPRK1 and Alzheimer disease.