The Efficacy of AZD1722 in Constipation Predominant Irritable Bowel Syndrome (IBS-C)

Inclusion Criteria: * Females and males must agree to use appropriate methods of contraception or be sterile (with appropriate documentation) * Subject is ambulatory * Subject meets definition of IBS-C using Rome III Criteria for the Diagnosis of IBS with a history of \<5 SBMs per week * Subject meets Screening eligibility criteria (see below) * A colonoscopy based on AGA guidelines; every 10 years at ≥ 50 years old, or the occurrence of any warning signs (i.e., unexplained weight loss, non-hemorrhoid blood in stools) * Ability to communicate well with the Investigator and to comply with the requirements of the entire study, including an understanding of how to use the touch-tone telephone electronic diary. * Written informed consent and a willingness to participate in the study as it is described. * Daily access to a touch tone telephone. Exclusion Criteria: * Functional diarrhea as defined by Rome III criteria * IBS with diarrhea (IBS-D), mixed IBS (IBS-M), or unsubtyped IBS as defined by Rome III criteria * Diagnosis or treatment of any clinically symptomatic biochemical or structural abnormality of the GI tract within 6 months prior to screening, or active disease within 6 months prior to screening. Including but not limited to cancer, inflammatory bowel disease, diverticulitis, duodenal ulcer, erosive esophagitis, gastric ulcer, pancreatitis (within 12 months of screening), cholelithiasis, amyloidosis, ileus, non-controlled GERD, gastrointestinal obstruction or carcin…