Ethnopharmacological relevanceThe Suxiao Jiuxin Pill (SJP) has been used for treating chronic stable angina (SA) for more than 40 years in China. SJP is composed of two Chinese herbs and has the effect of activating blood and promoting qi, according to traditional Chinese medicine (TCM) theory. Aim of the studyThe study aims to determine the effects of adjunct SJP on conventional therapy in patients with SA which provides a complementary choice and its evidence for clinical medication for treating SA. Materials and methodsParticipants with SA were recruited and randomized 1:1 to either the SJP group or the control group for 24 weeks. Both groups received conventional treatment according to local tertiary hospital protocols, and the participants received additional SJP (composed of Ligusticum wallichii and Borneol) or placebo in treatment and control groups respectively. The primary outcome was the curative efficacy rate at week 4. Secondary outcomes are the curative efficacy rate, the total score of angina pectoris symptoms, CCS Angina Classification improvement, Seattle Angina Questionnaire (SAQ) score, TCM syndrome scores (TCMSS), and the curative efficacy rate of TCMSS. Adverse events and adverse drug reactions were observed and recorded for safety analysis. ResultsA total of 324 participants with SA from 13 hospitals in China were enrolled in this trial. Compared with the control group, the curative efficacy rate of SA, the curative efficacy rate of TCMSS significantly increased, and the total score of angina pectoris symptoms and TCMSS significantly reduced in the SJP group at week 4, 12, and 24, accompanied by the statistically significant improvement in the curative efficacy rate based on CCS grade reduction (all P < 0.05). Furthermore, the SAQ score (physical limitation, angina stability, and treatment satisfaction) was evaluated as the quality of life significantly improved after treatment (P < 0.05). The medication compliance, concomitant medication, and rates of adverse events were similar between the two groups (P > 0.05). ConclusionThe present prospective, multicenter, randomized, double-blind, placebo-controlled, clinical trial confirms that adjunct SJP to conventional treatment increased the curative efficacy and life quality of SA patients with no significant adverse drug reactions during the clinical application. Clinical trial registration(ID, ChiCTR1900021876, URL = http://www.chictr.org.cn/showproj.aspx?proj=34955).