Herbal medicine (Danggui Shaoyao San) for treating primary dysmenorrhea: A systematic review and meta-analysis of randomized controlled trials

• Danggui Shaoyao San (DSS; Dangguijakyak San or Tokishakuyakusan) is one of the herbal medicine (HM) for dysmenorrhea.
• One recent systematic review of suggested that HM might be promising for treating dysmenorrhea. However, this review analysis is outdated and the information was not complete.
• Four randomized clinical trials (RCTs) met our inclusion criteria. All of the included RCTs had a high risk of bias across their domains
• Our systematic review and meta-analysis provides suggestive evidence of the superiority of superiority of DSS over analgesics and placebo for dysmenorrhea.

Danggui Shaoyao San (DSS), a traditional herbal prescription, has long been used to treat menopause-related symptoms, including dysmenorrhea. We conducted a systematic review of randomized controlled trials to evaluate the efficacy of DSS for dysmenorrhea. We searched the following electronic databases through October 2015: PubMed; EMBASE; the Cochrane Library; AMED; five Korean databases (KoreaMed, DBPIA, OASIS, RISS, and KISS); three Chinese databases (CNKI, Wan Fang Database, and VIP), and one Japanese database (CiNii). The Cochrane criteria were used to assess the risk of bias for the individual studies. All randomized clinical trials (RCTs) of DSS or modified DSS were included. Data from all articles were extracted by two independent reviewers. Meta-analysis was used to pool the data. A total of 746 potentially relevant studies were identified, and four RCTs met our inclusion criteria. All of the included RCTs had a high risk of bias across their domains. Three RCTs showed favourable effects of DSS on response rate compared with conventional medicine, and a meta-analysis showed that DSS had superior effects compared to analgesics (RR: 1.31, 95%CI, 1.06–1.63, I2 = 73%). One RCT showed a beneficial effect of DSS on pain compared with placebo control. Our systematic review and meta-analysis provided suggestive evidence of the superiority of DSS over analgesics or placebo for dysmenorrhea. The quality of evidence for this finding was low to moderate because of a high risk of bias.