It is a randomized double-blind parallel phase IV study to compare Fenoverine and Trimebutine maleate in the efficacy and safety.

Study Hypothesis: Fenoverine is non-inferior to Trimebutine maleate in its efficacy and safety.

For subjects with IBS, Fenoverine and Trimebutine will be administered orally for 8 weeks; Fenoverine 100mg capsule three times a day and Trimebutine 150mg tablet three times a day. Because one is capsule and the other is tablet, double dummy design will be used. Efficacy is evaluated at the end of 8 weeks and safety will be followed for 4 more weeks after the end of the scheduled medication.

Inclusion Criteria:

• 18 years of age or older and 60 years of age or younger
• Diagnosed as irritable bowel syndrome using Rome III Criteria
• Female subjects of child-bearing potential are confirmed to have a negative urine beta-hCG test within 7 days prior to administration of initial dose of investigational products.
• Female subjects of child-bearing potential must agree to use contraceptive measures during study period.

Exclusion Criteria:

• Known allergy or hypersensitivity to investigational products or components of the formulation
• Past or current diagnosis of chronic liver disease (e.g., liver cirrhosis, acute hepatitis, alcoholic hepatitis, chronic alcohol abuse and HCC)
• Past or current diagnosis of Myopathy
• Subject with serious renal disease
• Known medical condition assessed by investigators as inappropriate for the study
• Continuous use of NSAIDS, analgesics, steroids, or other immunosuppressants.
• Continuous use of HMG-CoA reductase inhibitors or fibrates to lower blood lipid level
• Pregnant, lactating, or planning to be pregnant women
• Evidence of abuse of drugs or alcohol within 6 months prior to screening
• Participation in other clinical trials within 3 months prior to enrollment or elapse of less than 5 half lives of previous investigational product after last dose of it.
• Unable to submit informed consent or comply with the requirements of the study