The purpose of this study is to determine whether a 20- herb formulation, as a well characterised extract, is efficacious in treating irritable bowel syndrome (IBS) and also to identify efficacious and safe dosage of the formulation in treating IBS.

The Specific aims of the project are:

1. To determine whether a 20- herb formulation improves pain/ discomfort and disturbed bowel frequency in patients with Irritable Bowel Syndrome who have been disappointed with current conventional Western medicine.
2. To identify an optimal dosage of the 20- herb formulation that is safe and well tolerated for up to 8 weeks of treatment, among 2 dosages. This is determined by relief of symptoms of IBS in a dose escalation, placebo-controlled double- blind randomized clinical trial, in conjunction with indices of safety and tolerability.

Inclusion Criteria:

• Age 18- 75

• All IBS patients attending the Gastroenterology Clinic of the Prince Of Wales Hospital of Hong Kong.

• IBS diagnosed by Rome III criteria:

  • Recurrent abdominal pain or discomfort at least three days per month in the previous three months

  • Symptoms onset at least six months prior to diagnose

  • Pain or discomfort associated with two or more of the following:

    1. Improvement with defecation
    2. Onset associated with change in frequency of stool
    3. Onset associated with a change in form (appearance) of stool

• Normal colonic evaluation (colonoscopy or barium enema) in past 5 years

• No "global symptom improvement" as rated by patients (see below) at screening and during the two- week run- in period to baseline

• Normal full blood count, liver function test and renal function test.

  • Informed written consent for participation into study.
  • Ethical approval will be obtained from the Joint CUHK-NTEC Clinical Research Ethics Committee as well as the IRB of UMB.

Exclusion Criteria:

• Past or present history of organic disease of gastrointestinal tract (e.g. colorectal cancer, advanced colonic polyp, celiac disease, inflammatory bowel disease, peptic ulcer and previous gastrointestinal surgery). (Note: those with polyps removed during colonoscopy can be included, as long as no known polyps remained.
• Systemic diseases that cause diarrhea or constipation (e.g. thyroid disease, diabetic neuropathy)
• Lactose intolerance
• Severe liver disease (e.g. cirrhosis, chronic active hepatitis)
• Renal impairment (serum creatinine level > 150mmol/L)
• Women who are pregnant, lactating or not practicing proper contraception
• Known hypersensitivity to herbal medicine
• Concommitant use of prescription antidepressant medication
• Current alcoholism and drug use
• Current psychiatric illness or dementia
• Fever or severe illness at baseline (week 0).