Background: Cough-variant asthma (CVA), a precursor of typical asthma, is the main cause of chronic cough. We hypothesize that yukmijihwang-tang (YJT), which has been used for chronic cough in traditional medicine and has been reported to have an anti-inflammatory effect, could be an adjuvant to asthma treatment. Methods: We plan a randomized, double-blind, placebo-controlled, multicenter, phase 2 trial to investigate the efficacy and safety of YJT in CVA patients. A total of 60 patients with CVA will be recruited and randomly assigned to either a high-dose YJT group, standard-dose YJT group, or control group (placebo) in a 1:1:1 allocation ratio after a 2-week run-in period. For the run-in period, only inhaled corticosteroids (ICSs) will be used, and the investigational drug will be administered once a day with concomitant ICS for 6 weeks. Data will be collected at baseline, week 3, and week 6, and the primary outcome measure will be the mean cough symptom score (CSS) change before and after medication. The secondary outcome measures will include the Leicester cough questionnaire-Korean version (LCQ-K) score, eosinophil count and eosinophil cationic protein level, pulmonary function test, and the number of uses of rescue medication, and so on. Conclusion: This study aimed to evaluate the efficacy and safety of YJT in concomitant treatment with ICS in patients with CVA and to determine the optimal dosage of YJT. The results are expected to provide evidence for the use of YJT as an adjuvant treatment for CVA.

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