The purpose of this study was to determine the dose-ranging efficacy and safety profile of encapsulated Bifidobacterium infantis 35624 in female subjects with irritable bowel syndrome (IBS).

The pathogenesis of irritable bowel syndrome (IBS) may have a a post-infectious inflammatory component, suggesting that altered gut bacterial flora are of relevance and that probiotics may be beneficial. This clinical trial examined the efficacy of an encapsulated probiotic in subjects with Rome II IBS. After a 2 week baseline, 362 female subjects were randomized to placebo or one of three doses of B. infantis 35624 once daily for 4 weeks. IBS symptoms were monitored daily and scored according to a 6-point Likert scale; stool frequency and form were also monitored daily. The primary efficacy variable was the abdominal pain score; secondary efficacy variables included other IBS symptom relief and quality of life.

Inclusion Criteria:

• Meet Rome II criteria for the diagnosis of IBS
• Refrain from using probiotic supplements during the trial

Exclusion Criteria:

• Organic diseases, including inflammatory bowel disease, and significant systemic diseases
• Subjects over 55 years of age that had not had a sigmoidoscopy or colonoscopy performed in the previous five years
• Use of anti-psychotic medications within the prior three months
• Had major psychiatric disorder (DSM-II-R or DSM-IV), including major depression, psychoses, alcohol or substance abuse, within the past two years
• Were pregnant or nursing
• Had known lactose intolerance or immunodeficiency
• Had undergone any abdominal surgery, with the exception of hernia repair or appendectomy