Systemic kappa opioid receptor agonists in the treatment of chronic pruritus: a literature review.

Chronic pruritus is frequently refractory to currently available treatments. Studies suggest that pruritus may arise from an imbalance of the mu- and kappa-opioid receptor system activity in either the skin or the central nervous system. Stimulation of kappa-opioid receptors by their agonists inhibits pruritus in both animals and humans. The antipruritic effect of kappa-opioid receptors agonists can currently be assumed to be related to their binding to kappa-opioid receptors on keratinocytes and cutaneous and/or central itch neurones. To date, several case reports and 2 controlled trials have demonstrated a beneficial effect of systemic kappa-opioid receptor agonists in the treatment of uraemic pruritus, prurigo nodularis, paraneoplastic and cholestatic pruritus. Nalfurafine hydrochloride (Remitch(®)), a selective kappa-opioid receptor agonist, is approved for the treatment of chronic pruritus in Japan. The aim of this review is to provide an overview of the promising role of kappa- opioid receptors and their agonist in the pathophysiology and treatment of pruritus.