Irritable Bowel Syndrome: Evidence-based Treatment

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Pharmacologic Treatment
Prescription and OTC medications serve an adjunctive role in the management of IBS.1 Efficacy trials in the IBS population are limited by disease heterogeneity, lack of disease markers, and high placebo response rates.19

Antispasmodics. Prescription antispasmodics, such as dicyclomine, have been shown to offer short-term relief of IBS-related abdominal pain; however, long-term outcomes are unknown. Possible adverse effects such as dizziness, dry mouth, blurred vision, and sluggishness may limit their use. Peppermint oil is considered an alternative to prescription antispasmodics and has been found to improve global IBS symptoms (RR, 2.25).12

Probiotics. A number of trials, systematic reviews, and meta-analyses have addressed the effect of probiotics on IBS symptoms. Meta-analyses found an RR of 0.72 to 0.77 for persistent IBS symptoms in patients using probiotics.20 Because probiotics can be beneficial, with relatively low cost and minimal associated risks, it is reasonable to consider a trial of probiotics, especially the specific strains offering the most promising results, such as Bifidobacterium infantis 35624 and Escherichia coli DSM 17252. Like most IBS treatments, it is unlikely that probiotics will benefit all IBS patients.20

Antidepressants. Tricyclic antidepressants (TCAs) and selective serotonin reuptake inhibitors (SSRIs) were found to be effective in reducing the risk for persistent IBS symptoms in adults (RR, 0.66; NNT, 4).12,18 TCAs can slow gastrointestinal transit time, which may be beneficial to patients with IBS-D but a drawback to those with IBS-C. SSRIs, such as fluoxetine, are especially appropriate for patients with concurrent anxiety or depression. Note that three to four weeks of treatment with antidepressants are required to see benefits.1

Others. Loperamide has been reported to significantly improve stool frequency and consistency in patients with IBS-D and IBS-M but not global IBS symptoms.1,2 Polyethylene glycol has been shown to be effective in treating adults with isolated constipation, but it was not superior to placebo in adults with IBS-C.21

A systematic review found that the 5-HT3 receptor antagonist alosetron offered clinical benefit to patients with IBS-D and IBS-M.22 However, due to reports of ischemic colitis and severe constipation, the FDA removed the drug from the US market in 2000. Ultimately, postmarketing data and patient demand brought the drug back onto the market in 2002, but it can be prescribed only with careful regulation and only for women with severe, refractory IBS-D.23,24

A locally acting chloride channel activator, lubiprostone, offers clinical benefit to patients with IBS-C and chronic constipation.25 Because of its unknown long-term effects, high expense, and lack of comparison data to other IBS-C treatments, this drug should only be given to women with severe refractory IBS-C.26

Two large multicenter RCTs found that a two-week course of rifaximin, a nonabsorbable antibiotic, reduced global IBS symptoms, especially bloating, in patients with IBS without constipation. The benefits continued through 10 weeks of follow-up.27 Prescribing rifaximin for the treatment of IBS is an off-label use and should be limited to patients with IBS-D who have not responded to currently available symptom-directed therapies. In addition, the lack of evidence for long-term benefits as well as the potential for development of antibiotic resistance should be borne in mind when using this drug.28

Linaclotide is approved for IBS-C, based on two large RCTs with 12- and 26-week follow-up periods. Treatment group participants reported substantial improvement in IBS-C symptoms. Approximately 5% of participants discontinued treatment due to ­diarrhea.29,30

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