Oral treatment with difelikefalin results in greater reductions in itch intensity scores than placebo among patients with notalgia paresthetica, but it does not improve secondary outcomes, according to a study published in the Feb. 9 issue of the New England Journal of Medicine.

Brian S. Kim, M.D., from the Icahn School of Medicine at Mount Sinai in New York City, and colleagues conducted a phase 2 trial involving patients with moderate-to-severe pruritus caused by notalgia paresthetica. Patients were randomly assigned to difelikefalin or placebo (62 and 63 participants, respectively).

In each group, the mean baseline Worst Itch Numeric Rating Scale (WI-NRS) was 7.6, indicating severe itch. The researchers found that the change from baseline in the weekly mean WI-NRS score at week 8 was −4.0 and −2.4 points in the difelikefalin and placebo groups, respectively. In general, the results from the secondary outcomes did not support those of the primary outcome. Compared with the placebo group, the difelikefalin group more frequently experienced headache, dizziness, constipation, and increased urine output.

"Among patients with notalgia paresthetica, the reduction in itch intensity over an eight-week period was modestly greater with difelikefalin treatment than with placebo," the authors write. "Larger and longer trials are required to determine the effect and risks of difelikefalin treatment in this disorder."

The study was funded by Cara Therapeutics, the manufacturer of difelikefalin.

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