Systematic review of topical capsaicin in the treatment of pruritus

Objective To determine the efficacy of topical capsaicin in treating pruritus in any medical condition. Data sources Cochrane library, Medline, Embase, Cinahl and Amed, up to April 2008. No language restrictions. Study selection Randomized, controlled trials comparing topically applied capsaicin with placebo or other standard treatment in patients with pruritus, independently selected by two reviewers. Data extraction Independently extracted by two reviewers. Quality assessed using the Jadad scale. Data synthesis Six randomized controlled trials were identified for inclusion. Three were for hemodialysis-related pruritus and provided insufficient data for the efficacy of topical capsaicin to be evaluated. A crossover study of capsaicin for treating idiopathic intractable pruritus ani reported a statistically significant difference in responder rates favoring capsaicin over placebo for itching scores but included insufficient data for the validity of this result to be assessed. A study on notalgia paresthetica reported a statistically significant difference in the first phase of a crossover study favoring capsaicin over placebo in a visual analogue scale for itch intensity but failed to report data for a second outcome measure. The final study on brachioradial pruritus used an inappropriate design and reported no significant reduction in itch between capsaicin and placebo. Conclusion At present, there is no convincing evidence for the use of capsaicin to treat pruritus in any medical condition. Further research is needed, and should attempt to address methodological issues identified through this review including unblinding and the suitability of crossover designs.