Herbal formula MaZiRenWan (Hemp Seed Pill) for constipation: A systematic review with meta-analysis

Background: There is growing interest in using herbal supplements to treat constipation; however, little evidence exists for their use.

Purpose: This study evaluates the efficacy and safety of herbal formula MaZiRenWan (Hemp Seed Pill, HSP) in patients with functional or non-functional constipation.

Study design: Systematic review and meta-analysis METHODS: PubMed, CENTRAL, Embase, CNKI, and Wanfang were searched through April 20, 2020 for randomized trials of HSP versus placebo or medications for all types of constipation. The primary outcomes were complete response rate, complete spontaneous bowel movement (CSBM), patient-reported satisfactory treatment rate (prSTR), and adverse events (AEs). Clinical data were analyzed using a random-effects model, and the quality of evidence was evaluated with the GRADE system.

Results: This review includes 1681 constipation patients from 17 moderate-to-high risk of bias trials that were conducted in east Asia. Two high-quality trials showed that HSP compared with placebo significantly increased weekly CSBM (mean difference, 0.95; 95% CI: 0.56, 1.35) and had a higher complete response rate (risk ratio [RR], 1.43; 95% CI: 1.20, 1.71) in patients with functional constipation. Low-quality evidence showed significant improvement in prSTR in HSP compared with conventional medications (RR, 1.79; 95% CI: 1.42, 2.25). Additionally, HSP use did not increase AEs compared with no HSP (p = 0.99).

Conclusions: This study found that HSP was effective among Asian patients with functional constipation. Rigorous trials need to be conducted in clinical populations outside of east Asia and in those with non-functional constipation to increase the generalizability of the evidence.