Hiroai Okutani

1 Introduction Itch can be described as an unpleasant sensation leading to a scratching desire [1]. It is a common symptom in dermatological and systemic diseases but may also be a side effect of several drugs, including opioids [2, 3]. Opioids are often used in the clinic for pain management, but pruritus is often reported as a side effect [4-10].

1 INITIAL CONSIDERATIONS In this review, the authors present and discuss the currently available literature and summarize the current knowledge of the mechanisms underlying opioid-induced pruritus, their relationship with pain aspects, and the possible treatment options to counteract this phenomenon.

4.3 Study limitations This exploratory study is limited by the small sample size and future studies should investigate bigger cohorts in order to validate the alteration of highlighted miRNAs. Variable expression by genetic factors within subjects of the same group could be pointed out as a limitation, although the high variance of personal expression of miRNAs in humans depends on many confounding factors (Wu et al., 2018).