The use of 0.25% zinc pyrithione spray does not enhance the efficacy of clobetasol propionate 0.05% foam in the treatment of psoriasis

Background: It was discovered that Skin Cap (Cheminova Internacional S.A., Madrid, Spain), an over-the-counter psoriasis therapy with zinc pyrithione, contained clobetasol propionate and it was withdrawn from the market by the US Food and Drug Administration review. Some suggested that there might be a synergistic effect of zinc pyrithione with clobetasol propionate. Objective. We sought to evaluate the efficacy of clobetasol propionate 0.05% foam with and without the coadministration of a topical 0.25% zinc pyrithione spray in treating psoriasis involving sites other than the scalp. Methods: We conducted a randomized, double-blind, right/left study of patients with mild to moderate, generally symmetric, plaque-type psoriasis. Patients were assigned to treatment with clobetasol propionate foam on all psoriatic lesions and then randomly assigned to use zinc pyrithione spray to either the right or left side of their body (vehicle spray to be applied to the opposite side). There was a 2-week treatment phase (visits at baseline, week 1, and week 2) and a follow-up phase (visit at week 4), and all treatments were administered twice daily for 2 weeks. The primary Outcome measure was the change from baseline to week 2 in the composite score of the signs of psoriasis (erythema, scaling, plaque thickness) for symmetric target lesions. Results: A total of 25 patients were enrolled; 24 completed the trial and I was lost to follow up. Of those who completed the study, 63% (15 of 24) were men, and the mean age (+/- SD) was 50 years (+/- 12.2). After 2 weeks of therapy, the average decline in the composite score was 3.5 (+/- 1.8) for monotherapy (clobetasol propionate foam and vehicle) and, similarly, 3.3 (+/- 1.8) for clobetasol propionate foam plus zinc pyrithione spray (P = .5). Discussion: Zinc pyrithione spray does not appear to enhance the efficacy of clobetasol propionate foam after 2 weeks of therapy.