Class act is a feature of Clinical Correlations written by NYU 3rd and 4th year medical students. These posts focus on evidenced based answers to clinical questions related to patients seen by our students in the clinics or on the wards. Prior to publication, each commentary is thoroughly reviewed for content by a faculty member.
Commentary by Alexander Jow, MSIII
Irritable bowel syndrome (IBS) is a poorly understood disorder, commonly encountered in clinical practice; IBS accounts for more than one-third of all referrals to gastroenterologists (1). IBS is characterized by abdominal discomfort or pain occurring with changes in bowel habits (diarrhea, constipation, or mixed diarrhea and constipation) that are not explained by an established organic or biochemical abnormality (2). While management of IBS is now largely focused on treatment of the diarrhea or constipation component of IBS symptomatology, the disease’s complex pathophysiology has hindered development of optimal therapeutics. Those agents that have been marketed, Alosetron (Lotronex) and Tegaserod (Zelnorm), have since been withdrawn from the market or have seen their usage severely limited by the FDA. Further, use of a medication that controls diarrhea can precipitate constipation and vice versa. New approaches are sorely needed given the ubiquity of the disease and the significant cost, in terms of dollars and quality of life.
Many mechanisms have been proposed to explain the pathogenesis of IBS, though the most feasible invokes aberrant transmission of pain signals from the enteric to the central nervous system. Local bowel factors likely also play an important role by modulating the patients’ perception of abdominal symptoms. One such local factor, the colonic flora, has been implicated in IBS pathogenesis. This hypothesis proposes that ‘unfavorable’ gut flora, such as gas-producing bacteria, may predispose patients to gastrointestinal symptoms, such as abdominal bloating and flatulence. In order to counter-balance the effects from potentially symptom-inducing bacteria, oral administration of probiotic bacteria as live microbial food supplements, has been proposed. Probiotic bacteria, such as Bifidobacterium, Lactobacillus, and Streptocccus genera as well as yeasts of the Saccharomyces genus are believed to compete with, and replace “pathogenic” bacteria in the gut lumen (3). As therapeutics, probiotics would provide ease of administration with very low risk of adverse events, especially compared to those medications already marketed for IBS treatment (4).
Thus far, studies on probiotic efficacy in the treatment of IBS have yielded conflicting results. In a study done in 2000, administration of Lactobaccillus casei was not shown to improve disease symptoms (5). However, oral supplementation with Lactobaccillus plantarum was found to be effective in reducing flatulence and abdominal pain in two double-blind, placebo-controlled studies (6,7). A more recent study using a probiotic formulation, VSL#3, which contains a mixture of probiotic bacterial species, showed no significant differences in mean gastrointestinal transit measurements, bowel function scores, or global symptom relief, though it was effective at reducing bloating (8).
In conclusion, there is no definitive evidence showing that administration of probiotics is effective for treatment of IBS. Our understanding of IBS pathophyisology is limited, so perhaps future studies may provide the rationale for using probiotics in a subset of IBS patients.
References
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Drossman D et al. AGA Technical Review on Irritable Bowel Syndrome. Gastroenterology. 2002; 123:2108-2131.
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Cremonini, F., Talley, N. Irritable Bowel Syndrome: Epidemiology, Natural History, Health Care Seeking and Emerging Risk Factors. Gastroenterol Clin N Am. 2005 Jun; 34(2):189-204.
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Kolida, S., Saulnier D.M., Gibson, G.R. Gastrointestinal Microflora: Probiotics. Adv Appl Microbiol. 2006;59:187-219.
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Cremonini, F., Talley, N. Treatments targeting putative mechanisms in irritable bowel syndrome. Nat Clin Pract Gastroenterol Hepatol. 2005 Feb;2(2):82-8.
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O’Sullivan, M., O’Morain, C. Bacterial supplementation in the irritable bowel syndrome. A randomized double-blind placebo-controlled crossover study. Dig Liver Dis. 2000; 32:294-301.
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Niedzielin, K., Kordecki, H., and Birkenfeld, B. A controlled, double blind randomized study on the efficacy of Lactobacillus plantarum 299V in patients with irritable bowel syndrome. J. Gastroenterol Hepato. 2001; 13:1143-48.
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Nobaeck, S., Johansson, M.L., et al. Alteration of intestinal microflora is associated with reduction in abdominal bloating and pain in patients with irritable bowel syndrome. Am J Gastroenterol. 2000; 95: 1231-1238.
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Kim, H.J., Camilleri, M., et al. A randomized controlled trial of a probiotic, VSL#3, on gut transit and symptoms in diarrhea-predominant irritable blowel syndrome. Ailment Pharmacol Ther. 2003; 17:895-904.