Efficacy of switching to bilastine, a histamine H1 receptor antagonist, in patients with chronic spontaneous urticaria (H1-SWITCH): study protocol for a randomized controlled trial.

Chronic spontaneous urticaria (CSU) is characterized by the spontaneous appearance of wheals, angioedema, or both for > 6 weeks. Continuous treatment with H1-antihistamines is used as a first-line treatment for CSU. However, H1-antihistamine treatment leads to absence of symptoms in less than 50% of patients with CSU. Although Japanese guidelines for the diagnosis and treatment of urticaria recommend an increase in the H1-antihistamine dose or a switch to other H1-antihistamines, there is no evidence supporting a switch to other H1-antihistamines in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed dose. We will conduct a multicenter, open-label, non-inferiority, randomized, parallel, comparison study to determine if the efficacy of bilastine 20 mg is not inferior to that of a twofold H1-antihistamine dose increase in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed dose. This study will be performed at 15 academic hospitals in Japan, and the administration period (increasing the H1-antihistamine dose twofold vs. switching to bilastine 20 mg) will be 7 days. Participants (n = 150) will be randomized to either an increased H1-antihistamine dose or a switch to bilastine 20 mg at a 1:1 ratio. The primary endpoint, mean of the total symptom score of 5–7 days after the intervention, will be evaluated. The secondary objective is to determine if the safety of bilastine 20 mg regarding somnolence is superior to that of a twofold dose increase of H1-antihistamines. This will be measured by a change in the Japanese version of the Epworth Sleepiness Scale from baseline to 7 days after starting the intervention. This multicenter, open-label, non-inferiority, randomized, parallel, comparison study will be, to our knowledge, the first well-designed clinical study to evaluate the efficacy of a switch to other H1-antihistamines in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed doses. This trial will provide evidence of the efficacy and safety of bilastine when treatment is switched in patients with refractory CSU who are unresponsive to H1-antihistamines at the licensed dose. Japan Registry of Clinical Trials (jRCT), jRCTs051180105. Registered on 8 March 2019.