Changyanning Tablet for the Treatment of Diarrhea-Predominant Irritable Bowel Syndrome (IBS-D)

Inclusion Criteria: 1. Meet IBS-D Rome IV diagnostic criteria; 2. Age between 18 and 65 years old (including boundary value), regardless of gender; 3. IBS symptom severity scale (IBS-SSS) scores \> 175 points; 4. The weekly average score of abdominal pain in screening period is ≥ 3 points (The most severe abdominal pain in the past 24 hours every day, the pain score was 11 grades (0-10), NRS-11; Also the number of days of the stool character classification (Bristol stool scale) is type 6 or 7 ≥ 2 in a week; 5. Patients who voluntarily accept the program's plan of the project and signs the informed consent form. Exclusion Criteria: 1. Patients with serious or unstable heart, liver, kidney, immune, endocrine system and other diseases or malignant tumors; 2. Patients are affected by factors such as intellectual disorder, mental disorder and language; 3. Patients with gastrointestinal organic diseases or with malignant tumors, such as pancreatitis, intestinal adenoma (excluding polypectomy for more than half a month), intestinal diverticulum, colon or rectal cancer, inflammatory bowel disease, intestinal tuberculosis, etc; 4. Other diseases (such as hyperthyroidism, diabetes, chronic renal insufficiency, nervous system diseases, etc.) that affect digestive tract dynamics; 5. Complicated with tuberculosis peritonitis, gallstones, cirrhosis, chronic pancreatitis and other gastrointestinal diseases; 6. Allergic constitution or allergic to the components of the studied drug; 7. Pregnant or lactating women, and women with recent fertility plans; 8. Previous abdominal or pelvic surgery, such as cholecystectomy; 9. Patients with positive fecal occult blood; 10. During the screening period, drugs that affect gastrointestinal motility and function cannot be stopped, including parasympathetic inhibitors, such as scopolamine, atropine, belladonna, etc; Muscle relaxants, such as succinylcholine; Antidiarrheal agents such as loperamide, smecta, etc; Opioid preparations, etc; 11. Those who use probiotics (except those who eat yoghurt) or antibiotics within 8 weeks before enrollment in the study; 12. IBS drugs (except polyethylene glycol and loperamide) were used within 3 months before the study; 13. Those who regularly drink alcohol within 6 months before screening, i.e., drink more than 14 units of alcohol every week (1 unit=360 mL beer or 45 mL liquor or 150 mL wine with 40% alcohol); 14. Those who have participated in or are currently participating in other clinical trials within 1 month before screening; 15. The researcher believes that there are patients who are not suitable for inclusion.