Table 2.

Effectiveness of opioid agonists and antagonists.

Drug	Class	Effectiveness
Difelikefalin	KOR agonist	Worst Itching Intensity Numerical Rating Scale (WI-NRS) improved by 3 points or more in 51.9% of the patients in a double-blinded, randomized, controlled phase 3 clinical trial Itch-related quality of life in the 5-D itch scale and the skindex-10 significantly improved in the trial
Nalbuphine	KOR agonist MOR antagonist	Mean visual analog scale for pruritus significantly improved in an open-label trial (4.0 to 1.2 at 180 mg/day and 0.4 at 240 mg/day) Numerical rating scale for pruritus improved with nalbuphine 120mg, but not nalbuphine 60mg in a randomized, double-blind, placebo-controlled multi-center trial
Naltrexone	Nonselective opioid antagonist	Beneficial effect not demonstrated in a randomized, double-blind, placebo-controlled crossover study
Nalfurafine hydrochloride	KOR agonist	Significant reduction of pruritus shown in phase 3 clinical trial and open-label long-term study