Treatment of irritable bowel syndrome with herbal preparations: results of a double-blind, randomized, placebo-controlled, multi-centre trial

Background: Herbal medications have been used in many countries for the treatment of patients with irritable bowel syndrome. Controlled data supporting the efficacy of these treatments in patients with irritable bowel syndrome are lacking. Aim: To assess the efficacy and safety of a commercially available herbal preparation (STW 5) (nine plant extracts), the research herbal preparation STW 5-II (six plant extracts) and the bitter candytuft monoextract in patients with irritable bowel syndrome. Methods: Two hundred and eight patients with irritable bowel syndrome were recruited after standardized diagnostic work-up into a double-blind, placebo-controlled, multi-centre trial and were randomly assigned to receive one of four treatments: commercially available herbal preparation STW 5 (n = 51), research herbal preparation STW 5-II (n = 52), bitter candytuft monoextract (n = 53) or placebo (n = 52). The main outcome variables were the changes in total abdominal pain and irritable bowel syndrome symptom scores. Results: Two hundred and three patients completed the trial. STW 5 and STW 5-II were significantly better than placebo in reducing the total abdominal pain score (intention-to-treat: STW 5, P = 0.0009; STW 5-II, P = 0.0005) and the irritable bowel syndrome symptom score (intention-to-treat: STW 5, P = 0.001; STW 5-II, P = 0.0003) at 4 weeks. There were no statistically significant differences between the bitter candytuft mono-extract group and the placebo group (P = 0.1473, P = 0.1207). Conclusions: The commercially available herbal preparation STW 5 and its research preparation STW 5-II are both effective in alleviating irritable bowel syndrome symptoms.