Chinese herbal formula Tongxie Yaofang for diarrhea-predominant irritable bowel syndrome: study protocol for a randomized, multiple-blind, placebo-controlled trial

INTRODUCTION: Diarrhea-predominant irritable bowel syndrome (IBS-D) is a bowel disease with a high incidence. It significantly reduces the quality of life of patients and affects the patient's daily activities and mental health. No specific therapeutic medications for IBS-D have been found. Published clinical trials suggest that Chinese herbal formula Tongxie Yaofang (TXYF) for IBS-D may be effective. However, high-quality clinical evidence supporting its use in IBS-D is still lacking. This trial aims to evaluate the therapeutic effects and safety of TXYF for IBS-D in adults. METHODS/DESIGN: A randomized, multiple-blind, placebo-controlled trial will be conducted. It will consist of an 8-week intervention followed by a 3-month follow-up period. The target sample size is 96 IBS-D patients aged 18 to 65 years. The eligible participants will be randomly allocated to either TXYF or placebo group in a ratio of 1:1. Participants in the experimental group will take TXYF granules, while participants in the control group will be given TXYF placebo granules. The primary outcome will be the degree of IBS symptom severity measured using the scale of IBS symptom severity score. The secondary outcomes include: (a) stool frequency, and (b) stool consistency measured using the Bristol stool scale, (c) quality of life measured using the scale of IBS-quality of life, (d) anxiety measured using the self-rating anxiety scale, (e) depression measured by the self-rating depression scale, and (f) the safety of using TXYF and placebo. Safety monitoring and assessment will be undertaken throughout treatment. DISCUSSION: Chinese herbal formula TXYF consists of four Chinese herbs: Atractylodes macrocephala Koidz., Paeonia lactiflora Pall., Citrus × aurantium L., and Radix saposhnikoviae. It has been used for diarrhea for hundreds of years and may have a potential benefit in treating adults with IBS-D, but due to lack of high-quality evidence, we designed a randomized, multiple-blind, placebo-controlled trial to evaluate its therapeutic effects and safety. This trial will provide important data to guide the clinical practice of TXYF for the treatment of IBS-D in adults. TRIAL REGISTRATION: ISRCTN registry ISRCTN12453166. Registered on 23 March 2021.