Double-Blind Placebo-Controlled Trial of Dapsone in Antihistamine Refractory Chronic Idiopathic Urticaria

Background: Management of antihistamine refractory chronic idiopathic urticaria (CIU) has poorly defined therapeutic options. Objective: To evaluate the efficacy of dapsone (4,4'-diaminodiphenylsulfone) in antihistamine refractory CIU compared with placebo. Methods: Twenty-two patients with antihistamine refractory CIU were randomly assigned to 100 mg of dapsone daily or placebo for 6 weeks in a 14-week double-blind, placebo-controlled crossover trial. End points were measured from a daily diary that reflected the weekly hive score, the weekly itch score, and a visual analog scale (VAS) score. Secondary to a carryover effect, the first period results were analyzed as a parallel design that compared placebo with dapsone directly by using repeated-measures analysis. Results: After 6 weeks, the patients in the dapsone arm showed mean improvement over baseline in VAS (2.3 [95% CI, 0.6-4.1], P= .01), urticaria score (-3.5 [95% CI, -6.2 to -0.9], P= .01), and itch score (-4.8 [95% CI, -7.6 to -2.1], P= .001), whereas the placebo arm showed no improvement over baseline for VAS, urticaria, or itch scores. Dapsone showed greater improvement compared with placebo for itch (P= .047) and VAS (P= .04). Of the 22 patients, 3 showed complete resolution of hives and itch with dapsone, whereas 31% and 41% had ≥50% resolution of hives and itch, respectively. No serious adverse effects were observed with dapsone. Conclusion: To our knowledge, this is the first double-blind, placebo controlled study of dapsone in CIU and indicates that dapsone has efficacy in patients with antihistamine refractory CIU.