Background: Most dialysis patients develop pruritus, for which current treatment is unsatisfactory. Endogenous opioids may be involved in this pruritus. We studied the effect of the opioid antagonist naltrexone on the pruritus of haemodialysis patients.

Methods: Naltrexone 50 mg per day by mouth was given to 15 haemodialysis patients with severe resistant pruritus in a randomised, double-blind, placebo-controlled crossover trial. The naltrexone or placebo periods lasted 7 days each with a 7-day washout between the two periods. Pruritus was assessed by the patients on a visual analogue scale from 0 (no pruritus) to 10 (maximum), and mean daily scores were calculated. Plasma histamine and beta-endorphin levels were measured, and spontaneous and stimulated basophil histamine-release were determined.

Findings: The median pruritus scores at the end of the naltrexone treatment were 2.1 (interquartile range 1.5-2.15) for the naltrexone-placebo sequence and 1.0 (0.4-1.15) for the placebo-naltrexone sequence. The respective values before naltrexone was given were 9.9 (9.85-9.95) and 9.9 (9.3-10.0). Plasma beta-endorphin levels were normal and remained unchanged during the study. Plasma histamine levels were high (mean 2.32 [SD 0.11] ng/mL, normal < 1.0) and decreased after naltrexone (to 1.8 [0.09], p < 0.01). Basophils from haemodialysis patients stimulated by interleukin-3 plus IgE antibodies released high amounts of histamine. The increase was 78.3 (19.3)% compared with 26.6 (16.3)% for five normal controls (p < 0.01). Incubation of the basophils with naloxone, another opioid antagonist, prevented this effect.

Interpretation: Our data suggest short-term efficacy with few side-effects for the amelioration of uraemic pruritus with naltrexone.