One year long-term study on abuse liability of nalfurafine in hemodialysis patients.

Nalfurafine (nalfurafine hydrochloride, TRK-820, Remitch®) was launched as an anti-pruritic for uremic pruritus in hemodialysis patients in Japan in 2009. Since the drug is an opioid that mainly binds to κ-receptors and possesses κ-agonistic pharmacological properties and also binds partially, but very weakly, to μ-receptors, the abuse liability of the drug was assessed by using questionnaires in patients enrolled in a clinical trial evaluating the efficacy and safety of the drug. The clinical trial was conducted for up to 52 weeks in patients subjected to regular hemodialysis. End-stage renal disease (ESRD) patients with uremic pruritus (n = 146) were administered nalfurafine 5 μg intravenously after each hemodialysis session. 81 ESRD patients without uremic pruritus served as non-treatment controls. All pruritus patients answered the 3 questionnaires of "the Addiction Research Centre Inventory (ARCI)", "modified Short Opiate Withdrawal Scale (SOWS)", which provides a range of signs and symptoms of opiate withdrawal, and Severity of Dependence Scale (SDS), which measures the dependence potential of the drug. The control patients were tested with the ARCI and modified SOWS questionnaires. There were no significant differences between the nalfurafine group and control group in the ARCI and modified SOWS scales. Thus, no evidence of abuse liability was indicated in the results. Also, no significant differences in the blood pressure, respiratory rate, body temperature and pupil diameter were shown between the two groups.