Chinese herbal medicine for the treatment of cough variant asthma: a study protocol for a double-blind randomized controlled trial

BACKGROUND: Cough variant asthma (CVA) is one of the leading causes of chronic coughing. The main treatment is currently anti-inflammatory medication. However, the coughing may return or be aggravated and lung function may deteriorate once the anti-inflammatory treatment is stopped. The effect of Chinese herbal medicine (CHM) on chronic coughing is remarkable, but high-quality evidence supporting its effectiveness is still lacking. This trial aims to evaluate the safety and efficacy, especially the long-term efficacy, of CHM plus anti-inflammatory medications for the treatment of CVA. METHODS/DESIGN: A randomized placebo-controlled double-blind trial will be conducted. It will consist of a 3-month intervention followed by a 6-month follow-up period. The target sample size is 60 patients with CVA who are between 18 and 70 years old. The eligible subjects will be allocated randomly into the experimental or control group in a ratio of 1:1. Patients in the experimental group will take CHM granules (4.9 g twice daily), while patients in the control group will be given a matched placebo. An administration of salmeterol/fluticasone propionate combination for 12 weeks will be the basic therapy for the two groups. The primary outcome is the cough visual analog scales (CVAS). The secondary outcomes include quality of life, rate of symptom relapse, lung function, and blood tests. A safety assessment will also be performed during the trial. DISCUSSION: The evidence gathered by the trial will be a valuable addition to informing treatment options for patients with CVA. TRIAL REGISTRATION: http://www.chictr.org.cn, ID: ChiCTR-IOR-16009148. Registered on 3 September 2016. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s13063-018-3073-x) contains supplementary material, which is available to authorized users.