This double-blind, placebo-controlled randomized pilot clinical trial will test the hypothesis that granules of CDD-2105, a Chinese herbal medicine formula, will have efficacy in alleviating constipation and abdominal pain in individuals with IBS-C. Participants (n=78) will be randomly assigned to the treatment or placebo group in a 1:1 ratio, followed by 4 weeks of intervention and 4 weeks of follow-up.

This double-blind, placebo-controlled randomized pilot clinical trial will test the hypothesis that granules of CDD-2105, a Chinese herbal medicine formula, will have efficacy in alleviating constipation and abdominal pain in individuals with IBS-C. Participants (n=78) will be randomly assigned to the treatment or placebo group in a 1:1 ratio, followed by 4 weeks of intervention and 4 weeks of follow-up.Primary Objective: To determine the efficacy and safety of CDD-2105 granules for treating IBS-C.

Inclusion Criteria:

• 18-65 years adults
• Fulfill the clinically diagnosed with IBS-C based on the ROME IV criteria
• Abdominal pain intensity: weekly average of the worst daily (in the past 24 hours) abdominal pain score of ≥3.0 on a 0 to 10 point scale (based on the 2-week E-diary in screening)
• CSBM ≤ 2 times/week (based on the 2-week E-diary in screening)
• Understand and be able to follow written and oral instructions in Chinese
• Provide informed consent
• Able to use and complete 2-week E-diary for screening

Exclusion Criteria:

• Drug-induced or secondary causes of constipation
• Use of medications and/or supplements that may confound the study outcomes (including but not limited to antibiotics, steroid, analgesic drug, neuromodulator, prebiotics, symbiotics, or probiotics)
• Clinically significant colonoscopy or sigmoidoscopy examination findings after the onset of symptoms for patients who (1) is ≥50 years old; and/or (2) has family risk of colon-rectal cancer or familial polyposis syndromes; and/or (3) has alarm symptoms within 6 months before screening (unintentional weight loss: >10% in 3 months, blood in the stools not caused by hemorrhoids or anal fissures, fever of unknown origin, anemia)
• Clinically significant laboratory or imaging findings within 6 months before screening
• Recent history of mushy or watery stools within one month
• Allergic to Chinese herbal medicine or G6PD
• Abdominal surgeries within the past year (except laparoscopic appendectomy)
• Pregnancy, breastfeeding or plan to become pregnant with the study timeframe
• Any disease(s), condition(s) or habit(s) deemed by the investigators that would compromise the individual's ability to complete the study, e.g. serious psychiatric conditions, at the discretion of the investigators
• Any disease(s), condition(s) or habit(s) deemed by the investigators that would prevent participation in the study, e.g. participation in past or active clinical research, at the discretion of the investigators

The protocol, SAP, and de-identified data will be shared upon the researchers' request.

6 months

researchers' request

All the study drugs and placebo should be in the same package with the same drug appearance and blinded according to the randomized numbers of the subgroups. The specific blinding method is set as follows: the study drugs and placebo are uniformly packaged and numbered according to the corresponding randomized group results. One copy of the blinding letter in duplicate is sent with the test drug to the project leader of the test center for storage, and the other copy is kept by the pharmacy until the end of the trial.