A double-blind evaluation of topical capsaicin in pruritic psoriasis

Background: Substance P, an undecapeptide neurotransmitter, has been implicated in the pathophysiology of psoriasis and pruritus. Objective: Safety and efficacy of topical capsaicin, a potent substance P depletor, were evaluated in patients with pruritic psoriasis. Methods: Patients applied capsaicin 0.025% cream ( n = 98) or vehicle ( n = 99) four times a day for 6 weeks in this double-blind study. Efficacy was based on a physician's global evaluation and a combined psoriasis severity score including scaling, thickness, erythema, and pruritus. Results: Capsaicin-treated patients demonstrated significantly greater improvement in global evaluation ( p = 0.024 after 4 weeks and p = 0.030 after 6 weeks) and in pruritus relief ( p = 0.002 and p = 0.060, respectively), as well as a significantly greater reduction in combined psoriasis severity scores ( p = 0.030 and p = 0.036, respectively). The most frequently reported side effect in both treatment groups was a transient burning sensation at application sites. Conclusion: Topically applied capsaicin effectively treats pruritic psoriasis, a finding that supports a role for substance P in this disorder.