Effectiveness of Probiotics in the Treatment of Irritable Bowel Syndrome

Sheila M. Wilhelm, PharmD; Christine M. Brubaker; Elizabeth A. Varcak; Pramodini B. Kale-Pradhan, PharmD


Pharmacotherapy. 2008;28(4):496-505. 

In This Article

Abstract and Introduction


Recently, the use of tegaserod and alosetron—drugs approved for the treatment of irritable bowel syndrome (IBS)—has been restricted because of adverse events. This has resulted in a need for additional modalities for the treatment of IBS. Our objective was to determine the effectiveness of probiotics in the global relief of symptoms associated with IBS and in the improvement of flatulence, abdominal pain, transit time, and bacterial counts. Using the MEDLINE database from 1966-October 2007 and manually searching article references for relevant articles and abstracts, we identified 14 blinded, placebocontrolled clinical trials of the effectiveness of probiotics in the treatment of IBS. Of 11 studies in which overall symptom relief was assessed, seven indicated a significant improvement with probiotics versus placebo. Five of eight investigations of abdominal pain and distention revealed a benefit with probiotic use. Four studies demonstrated an improvement in symptomatic flatulence in probiotic treatment groups, whereas one study showed no significant benefit. Four of five studies of the effects of probiotics on colonic transit time revealed a benefit compared with placebo. As probiotics have shown benefit and possess a favorable adverse-effect profile, their use may represent an option for symptom relief in patients with IBS. However, additional data are necessary before probiotics can become a standard of care in the treatment of IBS, a complex and chronic condition.


Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders in the United States. A chronic condition, IBS is associated with symptoms of abdominal pain, abdominal distention, and changes in bowel habits.[1] Depending on a person's bowel habits, IBS can generally be categorized as constipationpredominant IBS, diarrhea-predominant IBS, or IBS with alternating bowel habits.[2]

The etiology of IBS is unknown. However, alterations in gastrointestinal motility, visceral hypersensitivity, mucosal inflammation, and postinfectious development have all been proposed as pathologic mechanisms of IBS.[1,3] Psychosocial factors are associated with IBS but are not considered in its diagnostic criteria. According to the Rome II criteria, IBS is diagnosed when abdominal discomfort or pain demonstrates two of the following three features for at least 12 weeks (which need not be consecutive) in the preceding 12 months: relief with defecation, an onset associated with a change in frequency of stool, and/or an onset associated with a change in the form (appearance) of the patient's stool.[4,5] The Rome II criteria further identify the following five symptoms that cumulatively support the diagnosis of IBS: abnormal stool frequency (which may be defined as > 3 bowel movements/day or < 3 bowel movements/wk), abnormal stool form (lumpy and hard or loose and watery stool), abnormal stool passage (straining, urgency, or a feeling of incomplete evacuation), passage of mucus, or bloating or feeling of abdominal distention. The diagnosis of a functional bowel disorder is always based on the presumption that a structural or biochemical explanation for the symptoms is absent.

Some experts hypothesize that bacterial overgrowth in the small intestine and imbalance of gastrointestinal flora may lead to symptoms of IBS.[3,6] Small-intestinal bacterial overgrowth increases fermentation and gas production in the small intestine, which may create a framework for the development of symptoms of IBS, such as abdominal bloating, pain, diarrhea, and constipation. Most treatments have targeted these mechanisms.

Recently, the use of tegaserod and alosetron—drugs approved for the treatment of IBS—has been restricted because of adverse events. This has resulted in a need for additional modalities for the treatment of IBS. Recent literature suggests that probiotics have been used in the treatment of IBS.[6] Probiotics are dietary supplements that contain viable bacteria and yeast that are typically part of the body's normal microbial flora.[7] The exact mechanism of action of probiotics has not been elucidated. Experts hypothesize that the agents competitively replace depleted colonies of normal flora and allow for relief of symptoms.[7,8] Many probiotics can inhibit the growth of pathologic bacterial strains. Studies have also suggested that certain strains of probiotics may stimulate an antiinflammatory response.[9,10] The supplements may also moderate visceral afferent hypersensitivity to alleviate symptoms. These observations have led to the investigation of probiotics in the treatment of IBS.


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