Nalfurafine hydrochloride for refractory pruritus in peritoneal dialysis patients: a phase III, multi-institutional, non-controlled, open-label trial

Emerging Therapeutic Options for Chronic Pruritus

Chronic pruritus, defined as an unpleasant sensation resulting in a need to scratch that lasts more than 6 weeks, is a prevalent and bothersome symptom associated with both cutaneous and systemic conditions. Due to complex pathogenesis and profuse contributing factors, chronic pruritus therapy remains challenging. Regardless of the well-established antipruritic properties of classic pharmacotherapy (topical therapy, phototherapy and systemic therapy), these methods often provide insufficient relief for affected individuals. Owing to the growing interest in the field of pruritic research, further experimental and clinical data have emerged, continuously supporting the possibility of instigating novel therapeutic measures. This review covers the most relevant current modalities remaining under investigation that possess promising perspectives of approval in the near future, especially opioidergic drugs (mu-opioid antagonists and kappa-opioid agonists), neurokinin-1 receptor antagonists, biologic drugs, Janus kinase inhibitors, ileal bile acid transporter inhibitors, aryl hydrocarbon receptor agonists and histamine H₄ receptor antagonists.

Clinical Profiles of Nalfurafine Hydrochloride for the Treatment of Pruritus Patients

Nalfurafine hydrochloride is a selective kappa-opioid agonist that has antipruritic effects. Here we describe the clinical trials for treatment of uremic pruritus in dialysis patients and on hepatic pruritus in patients with chronic liver disease. Among cytochrome P-450 (CYP) isoforms in humans, CYP3A4 is the major isoform involved in metabolic decyclopropylmethylation of nalfurafine hydrochloride. Nalfurafine hydrochloride was found to be a substrate for P-glycoprotein (P-gp), but had no inhibitory effects on P-gp-mediated transport. The efficacy of oral nalfurafine hydrochloride at 2.5 and 5 μg for refractory pruritus in hemodialysis patients was observed within the first 7 days of treatment, and the effects persisted for the 52-week treatment period. Nalfurafine hydrochloride is also effective in the treatment of conventional refractory pruritus in peritoneal dialysis patients. Moreover, nalfurafine hydrochloride at 2.5 and 5 μg is effective for the treatment of refractory pruritus in chronic liver disease patients within the first 7 days of drug administration. In all the clinical trials, most adverse drug reactions (ADRs) were mild and resolved quickly and there was no clinical safety problem. Following 52 weeks of treatment, hemodialysis patients did not develop physical or psychological dependence, indicating no addiction risks. In summary, nalfurafine hydrochloride administered orally at doses of 2.5 and 5 μg was safe and effective for treatment of refractory pruritus in patients undergoing hemodialysis or peritoneal dialysis and in chronic liver disease patients.

Can we use psychoactive drugs to treat pruritus?

Pruritus is a frequent complaint both in dermatology and general medicine. This burdensome symptom has a complex and multifactorial pathogenesis, with the key involvement of central nervous system in its development. Psychoactive drugs (psychopharmaceuticals) encompass several therapeutic groups utilized mainly in psychiatry. However, these drugs are occasionally used in dermatological practice and may contribute to alleviation of pruritus in a variety of cutaneous and extracutaneous disorders. This review article summarizes the role of H1-antihistamines, antidepressants, antipsychotics and antiepileptics in managing pruritus.