UREMIC PRURITUS - ROLES OF PARATHYROID-HORMONE AND SUBSTANCE-P

Background: Most patients receiving maintenance hemodialysis have prur itis, but its underlying mechanism remains unknown. Secondary hyperpar athyroidism is another common problem in these patients, but its role in uremic pruritus is controversial. Capsaicin can deplete substance P from the peripheral neurons and is known to be effective in the treat ment of pain and itching. Objective: Our purpose was to evaluate the r ole of parathyroid hormone (PTH) and substance P in uremic pruritus an d to elucidate the underlying mechanisms. Methods: The study contained two phases. In phase I, we analyzed the correlation between the inten sity of itching and serum levels of intact PTH. In phase II, patients with moderate to severe pruritus were placed into two groups: one with high PTH levels and one with low levels. A double-blind, placebo-cont rolled study of capsaicin 0.025% cream was conducted in phase II. Resu lts: Serum levels of intact PTH did not correlate with the intensity o f pruritus and did not significantly change during treatment with caps aicin or placebo. Capsaicin was significantly more effective in allevi ating uremic pruritus than the placebo, and no serious side effects we re noted. Conclusion: Uremic pruritus is not related to PTH. Substance P may act as a neurotransmitter in uremic pruritus and topical capsai cin can be used in the treatment of localized pruritus.