Efficacy and safety of Zihua Wenfei granules in treatment of postinfectious cough (wind-cold invading lungs syndrome): study protocol for a randomized controlled trial

Background Postinfectious cough usually develops and persists following respiratory tract infection. The protracted cough is embarrassing and troublesome and significantly impairs daily life. However, the optimal treatment available for this condition is still not known. This study aims to investigate the efficacy and safety of a new Chinese herbal prescription, Zihua Wenfei granule (ZHWFG), in treatment of postinfectious cough (wind-cold invading lungs syndrome). Methods This study is a prospective, multi-center, randomized, double-blinded, parallel group, placebo-controlled trial. A total of 216 adult participants with postinfectious cough will be enrolled from six study centers across China. All participants are randomly allocated to one of three parallel treatment groups: (1) 15 g of active ZHWFG three times daily, (2) 10 g of active ZHWFG plus 5 g of ZHWFG-matched placebo three times daily, and (3) 15 g of ZHWFG-matched placebo three times daily. The treatment duration is 14 consecutive days. The primary outcomes are cough resolution rate and cough relief rate. Secondary outcomes include time to cough resolution, time to cough relief, change from baseline in cough symptom score, cough visual analog scale value, traditional Chinese medicine syndrome score at days 7 and 14, and change of CQLQ from baseline to post-treatment as well as adverse events. Discussion This trial may not only investigate the efficacy and safety of ZHWFG in the management of postinfectious cough (wind-cold invading lungs syndrome), but also add the evidence of Chinese herbal medicine in treatment of postinfectious cough and provide an alternative option for the management of postinfectious cough. Trial registration ChiCTR1900022078. Registered on 23 March 2019. http://www.chictr.org.cn/showproj.aspx?proj=36547 .