UREMIC PRURITUS AND EXPOSURE TO DI(2-ETHYLHEXYL)PHTHALATE (DEHP) IN HEMODIALYSIS-PATIENTS

Uraemic pruritus is a frequent and disabling symptom in patients on di alysis. The pathogenesis of uraemic pruritus is nevertheless still obs cure. We investigated whether di(2-ethylhexyl)phthalate (DEHP), the mo st commonly used plasticizer in polyvinylchloride (PVC) haemodialysis tubings, is a possible pathogenetic factor in uraemic pruritus. Serum concentrations of DEHP and its major derivatives mono-(2-ethylhexyl)ph thalate (MEHP), 2-ethylhexanol (2-EH) and phthalic acid (PA) were dete rmined in uraemic patients before and after a haemodialysis session an d compared with the occurrence and intensity of pruritus in these pati ents. Twenty-one patients on regular haemodialysis for at least 6 mont hs were examined. The severity of uraemic pruritus was assessed using a standard questionnaire (pruritus score). The quantitative analysis o f DEHP and its derivatives was carried out by GC/selected ion monitori ng mass spectrometry. Fourteen out of 21 patients (66%) complained abo ut uraemic pruritus to a variable degree. The post-dialysis serum conc entrations of DEHP, MEHP and 2-EH were significantly higher than the c orresponding pre-dialysis values, whereas the postdialysis concentrati ons of PA (0.122 +/- 0.078 mu g/ml) were significantly lower than pre- dialysis levels (0.194 +/- 0.101 mu g/ml, P=0.00068). Neither pre- nor post-dialysis serum concentrations of DEHP, MEHP, PA or 2-EH were cor related with the severity of uraemic pruritus. Additionally, serum con centrations of DEHP and its metabolites did not differ significantly i n patients with and without pruritus. These findings suggest that pati ents on haemodialysis are regularly exposed to considerable amounts of DEHP and metabolites. Phthalic acid, one of the presumed end products of DEHP metabolism, might be eliminated at least in part by haemodial ysis. The exposition to DEHP and metabolites during haemodialysis, as assessed by measuring serum concentrations, bears no immediate relatio n to the occurrence or intensity of uraemic pruritus.