Colpermin ® (Peppermint oil) is used in the treatment of Irritable Bowel Syndrome but Peppermint (Mentha x piperita) isn't native in Iran. So in this study the Enteric-Coated of Anise-oil will formulate and use in treatment of Irritable Bowel Syndrome with pain and bloating.

The purpose of this study is to assess the efficacy of Enteric-coated Anise-oil capsules comparing with placebo and Colpermin® for treatment of IBS patients. 120 patients with confirmed IBS with non-response criteria selected. In this double blind pilot study, the patients and researchers will be blinded about Receiving Drug, Placebo and Active allocation. Patients will be randomized into group A (Anise-oil EC Capsule 187 mg daily, for 4 weeks), group B (placebo Capsule once daily, for 4 weeks) and group B (Colpermin® Capsule once daily, for 4 weeks). At the end of therapy (4 weeks) and at baseline (first), 2 weeks after receiving drug, placebo and Colpermin® IBS load, will be evaluated and compared between groups.

Inclusion Criteria:

• Meeting the Rome III Modular Questionnaire
• Patients with 50 years were required to have a colonoscopy performed within the previous 5 years
• Patients under the age of 50 years were required to have a sigmoidoscopy performed

Exclusion Criteria:

• Unable or unwilling patients to use an acceptable method of birth control
• Pregnant or nursing females
• Previous gastrointestinal or abdominal surgery (except for common causes unrelated to IBS)
• Organic disorder of the large or small bowel (e.g. ulcerative colitis, Crohn's disease)
• Mechanical obstruction
• Unexplained significant weight loss or rectal bleeding
• Diagnosis of any medical condition associated with constipation (other than IBS)
• Cancer
• Abnormal laboratory tests
• Abuse of alcohol or drugs