Inclusion Criteria:

• Men or women aged 18-70

• Diagnosis of irritable bowel syndrome based on the following criteria (ROME II): At least 12 weeks, which need not be consecutive, in the preceding 12 months of abdominal discomfort or pain (at least once per week) with at least 2 of the following features:

  • Relief with defecation;
  • Onset associated with a change in stool frequency;
  • Onset associated with a change in stool consistency.

• At least two of the following on at least 25% of occasions or days in the last 3 months:

  • Fewer than three bowel movements a week;
  • More than three bowel movements a day;
  • Hard or lumpy stools;
  • Loose (mushy) or watery stools;
  • Straining during a bowel movement;
  • Urgency;
  • Feeling of incomplete bowel movement;
  • Passing mucus during a bowel movement;
  • Abdominal fullness, bloating or swelling.
• Women of childbearing potential must be using an acceptable method of contraception.

Exclusion Criteria:

• History of severe or intractable IBS, defined as continuous, unremitting and severe abdominal pain greater than 12 hours/day
• Concurrent diagnosis of any bowel disturbance that would interfere with the assessment or safety of the study
• History of laxative abuse
• Previous abdominal surgery (uncomplicated appendectomy, hysterectomy or cholecystectomy at least 6 months prior to entry acceptable)
• History of metabolic or inflammatory disease that may affect bowel motility, eg., inflammatory bowel disease, diabetes mellitus, sarcoidosis
• Use of the following concomitant medications: medications that can affect gastrointestinal (GI) motility; other investigational drug use (30 day "washout" required); medications affecting visceral perception; antidepressants; selective serotonin reuptake inhibitors; opioids; narcotic analgesics; antispasmodic and anticonvulsant agents; insulin or other hypoglycemic therapy; thyroid hormones; central nervous system (CNS) depressants.
• Other significant illness as determined by Investigator
• Pregnancy
• History of drug or alcohol abuse within 2 years
• Insufficient knowledge of English or Hebrew to complete self-assessments to participate in study
• Any other reason for which Investigator feels that subject's compliance is at question or safety may be compromised.