ABSTRACT
BACKGROUND: Postinfectious cough (PIC) is a common symptom following a respiratory tract infection. Xingbei Zhike (XBZK) granules, a Chinese patent medicine, has been widely used for PIC in clinics. However, there is a lack of evidence on the effectiveness. PURPOSE: To investigate whether treatment with XBZK granules is effective for PIC. STUDY DESIGN: A multicenter, randomized, double-blinded, placebo-controlled trial. METHODS: Eligible participants from fourteen hospitals were randomly assigned in 3:1 ratio to receive either XBZK granules or placebo for 14 days. The primary outcome was the area under the curve (AUC) of a visual analogue scale (VAS) for cough symptoms. Secondary outcomes included cough symptom score (CSS), time and probability of recovery from cough, traditional Chinese medicine (TCM) syndrome score, relief rates of individual symptoms, Leicester Cough Questionnaire (LCQ) score, and the use of reliever drug. RESULTS: A total of 235 patients (176 in XBZK and 59 in placebo groups) were included in the analysis. The AUC for cough VAS scores was lower in the XBZK than placebo group (-8.10, 95 % CI -14.12 to -2.07, p = 0.009), indicating superiority. XBZK decreased CSS (-0.68 points, 95 % CI -1.13 to -0.22, p = 0.01), shortened time to cough recovery (-2 days, hazard ratio [HR] 1.48, 95 % CI 1.03 to 2.13, p = 0.02), enhanced the probability of cough recovery (risk ratio [RR] 1.66, 95 % CI 1.07 to 2.58, p = 0.03), lowered TCM syndrome score (-0.99 points, 95 % CI -1.58 to -0.40, p = 0.004), increased the rate of daytime (RR 1.84, 95 % CI 1.07 to 3.15, p = 0.02) and nighttime (RR 2.07, 95 % CI 1.29 to 3.35, p = 0.004) cough recovery, and reduced the viscosity of sputum (RR 2.92, 95 % CI 1.66 to 5.13, p < 0.001) compared to placebo. There were no significant differences in LCQ scores and taking reliever drugs between groups. No severe adverse events were reported in either group. CONCLUSIONS: XBZK granules are a promising therapy against PIC, effective in lowering the overall severity of cough, shortening the time to cough recovery, and reducing the viscosity of sputum.