Certain opioids are proving to be effective in treating a variety of itch conditions, according to Brian S. Kim, MD.
Dr. Brian S. Kim
“We know that opioids or opiates do cause itch in a significant number of patients,” Dr. Kim, a dermatologist who is codirector of the Center for the Study of Itch & Sensory Disorders at Washington University, St. Louis, said during MedscapeLive’s annual Las Vegas Dermatology Seminar. “It’s thought to do this by way of acting as a pruritogen at times and stimulating sensory neurons [that] then activate the itch cascade. But it’s also been well known that endogenous kappa opioids can activate sensory neurons that can then suppress itch and gate out signals from these opiates, but perhaps other pruritogens as well.”
Multiple drugs differentially target kappa-opioid receptor (KOR) and mu-opioid receptor (MOR) pathways, he continued. For example, oral naltrexone is a MOR antagonist, oral nalfurafine and intravenous difelikefalin are KOR agonists, while intranasal butorphanol and oral nalbuphine have a dual mechanism.
Difelikefalin is the first Food and Drug Administration–approved treatment for uremic pruritus associated with dialysis, approved in August 2021 for moderate-to-severe pruritus associated with chronic kidney disease in adults undergoing hemodialysis; it is administered intravenously. During the 2021 annual congress of the European Academy of Dermatology and Venereology, Dr. Kim and colleagues presented findings from a phase 2 trial of 401 people with atopic dermatitis (AD) and moderate to severe pruritus, who were randomized to receive oral difelikefalin at a dose of 0.25 mg, 0.5 mg, or 1.0 mg, or placebo over a 12-week treatment period. The primary endpoint, change from baseline in Itch Numerical Rating Scale score, was not met in any of the difelikefalin dose groups in the overall study population, but patients with a body surface area of less than 10% experienced a significant improvement in itch at week 12 in the combined difelikefalin dose group in (P = .039). A significant reduction in itch with difelikefalin was seen in this group of patients with itch-dominant AD, as early as the second day of treatment.
In another trial, 373 hemodialysis patients with moderate or severe uremic pruritus were randomized in a 1: 1:1 ratio to nalbuphine extended-release tablets 120 mg, 60 mg, or placebo and treated for 8 weeks. The researchers found that nalbuphine 120 mg significantly reduced the itching intensity. Specifically, from a baseline numerical rate scale (NRS) of 6.9, the mean NRS declined by 3.5 and by 2.8 in the nalbuphine 120-mg and the placebo groups, respectively (P = .017).
In a separate, unpublished multicenter, randomized, phase 2/3 trial, researchers evaluated the safety and antipruritic efficacy of nalbuphine extended-release tablets dosed twice daily at 90 mg and 180 mg in 62 patients in the United States and Europe. The proportion of patients in the nalbuphine 180-mg arm who met 50% responder criteria at week 10 or last observed visit approached statistical significance (P = .083), and this arm met statistical significance for patients who completed treatment (P = .028).
Dr. Kim disclosed that he has served as a consultant for AbbVie, AstraZeneca, Cara Therapeutics, Galderma, GlaxoSmithKline, LEO Pharma, Lilly, Pfizer, Regeneron, Sanofi, Trevi Therapeutics. He also has conducted contracted research for Cara Therapeutics and LEO Pharma.
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