Modulation of mu-opioid pathway for the treatment of pruritus: a systematic review of 1,146 patients

BACKGROUND: Pruritus is a debilitating symptom and conventional therapies often provide incomplete relief. The μ-opioid receptor (MOR) pathway is a key regulator of itch, and μ-pathway-modulating agents are increasingly used off-label for refractory pruritus. AIM: This systematic review evaluates the efficacy, safety, and real-world use of μ-opioid pathway modulators for pruritus of dermatologic and systemic origin. METHODS: = 351). Owing to substantial clinical and methodological heterogeneity, findings were narratively synthesized. RESULTS: Five RCTs evaluated dermatologic conditions, including atopic dermatitis, prurigo nodularis, chronic urticaria, and lichen planopilaris, while nine RCTs assessed systemic pruritus, predominantly cholestatic and uremic pruritus. RCTs investigated oral or topical naltrexone, intravenous naloxone, nalmefene, and extended-release nalbuphine, with most demonstrating clinically meaningful reductions in pruritus intensity using validated itch scales. Non-randomized studies reported improvement across a wide range of dermatologic and systemic conditions, with adverse events generally mild and well tolerated. CONCLUSIONS: Overall, μ-opioid pathway modulators show promising efficacy with acceptable short-term safety across diverse pruritic conditions, although larger high-quality RCTs are required to define optimal dosing and support clinical translation.