Effect of oral cromolyn sodium on CKD-associated pruritus and serum tryptase level: a double-blind placebo-controlled study.

BACKGROUND Generalized pruritus is a significant complication in end-stage renal disease patients. The mechanism is unknown and most treatments are ineffective. This study is the first clinical trial designed to evaluate the effect of cromolyn sodium (CS) on renal itch. METHODS Sixty-two haemodialysis (HD) patients with pruritus were enrolled into the study and were randomly assigned to receive CS or placebo (135 mg three times daily) for 8 weeks. Patients were asked to record the severity of their pruritus on each dialysis session on a visual analogue scale (VAS) during the 8 weeks of treatment and 4 weeks following discontinuation of treatment. Serum tryptase levels were determined at baseline, after 8 weeks of treatment and 4 weeks after discontinuation of treatment. RESULTS Data were analysed in 21 patients in the CS group and 19 patients in the placebo group that completed the study. A significant difference was seen in the severity of pruritus between the two groups during the period of study. Level of pruritus decreased from 8.48 +/- 2.2 to 0.9 +/- 1.8 after 8 weeks of treatment with CS. Geometric mean of serum tryptase at baseline and 8 weeks after treatment were 21.3 and 19.5 ng/ml for the CS group and 18.03 and 18.2 ng/ml for the placebo group, respectively. Although the geometric mean of tryptase had decreased in the CS group, this decrease was not statistically significant (P = 0.214). CONCLUSION CS can significantly reduce the severity of pruritus in HD patients, but this effect is not due to a decrease in serum tryptase level.