Clinical Trials of N-acetyl Glucosamine Capsule for IBS-D Treatment

Inclusion Criteria: * Voluntarily signed the informed consent form. * Man or woman, aged 18 to 65 years, inclusive. * Based on the Roman III diagnostic criteria for diagnosis of IBS-D subjects, recurrent abdominal pain accompanied with abdominal discomfort or not, monthly attack within the past 3months at least 3 days. With two or more of the following three kinds of symptoms: At least a portion of the time abdominal pain or defecate increase when discomfort. At least a portion of the time abdominal pain or the row of loose stools when discomfort. At least a portion of the time abdominal pain or discomfort improved after defecation. Symptoms for at least 6 months before diagnosis. * Screening/import period pain intensity scores of the NRS week mean value are 3.0 plus and the days which at least more than one time a stool type are 6 or 7 type over 2 days per week. * During the screening period，patients should answer the questions of electronic log completely following the requirements for 10days or more. * Patients are willing to stop drugs for abdominal symptoms or diarrhea which are in violation of the scheme, and take medicine prescribed in the scheme. * Patients agree to not change the lifestyle significantly that may affect the symptoms of IBS-D from signing up the Informed Consent Form to the last experiment. * The illness recured after a normal colonoscopy report within one year that was provided by this hospital or a grade first class teaching hospital, include polyp of colon (less than 3mm,the number of less than 5) patients who taked therapeutic endoscopy and recurrenced within one year; or those that get a normal colonoscopy report in this hospital or a grade first class teaching hospital before screening but have a history of bowel preparation, should be chosen when next attack. Exclusion Criteria: * History of organic gastrointestinal diseases: Chronic pancreatitis (cp), inflammatory bowel disease, intestinal tuberculosis, malabsorption syndrome, celiac disease, gastrointestinal tumor, or other organic diseases etc. * History of abdominal and pelvic surgery ( not including appendectomy and intestinal polyposis (\<3mm) after treatment within one year ). * The non-intestinal disease of digestive system such as Peptic ulcer, tuberculous peritonitis, cirrhosis etc. * Heart, lung, kidney and other important organs have severe lesions, immune regulatory disease, metabolic disease (diabetes, thyroid disease) or malignant tumor, reproductive system diseases such as ovarian cysts, endometriosis, etc. * Laboratory tests or Electrocardiogram were significantly abnormal, and judging by the researchers may damage the patient safety or successful completion of the clinical research: Male hemoglobin \<120g/L, female hemoglobin \<100g/L; Male serum creatinine≥133umol/L, female serum creatinine≥124umol/L; or creatinine clearance rate≤60ml/min; Chronic liver disease and/or abnormal liver function, defined as AST (aspartate aminotransferase) \> 1.5 x ULN (Upper Limit Of Normal) and/or ALT (alanine aminotransferase) \> 1.5 x ULN and/or total bilirubin \> 1.5x ULN; * Serious psychiatric patients( Hamilton Depression Scale scores\>20). * History of drug abuse or alcohol abuse. * Allergic to this study drug. * Concomitant medication is unable to stop or use continuously for more than a week but affect the gastrointestinal movement and function in the experiment, such as antibiotic drugs, the drugs of regulating the intestinal microecology, parasympathetic inhibitors, muscle relaxants, antidiarrheal, opiates, etc. * Do not fill in the electronic log of one week before entering the group (-1 week) completely. * Pregnant or lactating women * Is participating in clinical trials or have finished it less than 3 months. * Other researchers think not suitable for the list.