Update on the Management of Diarrhea-Predominant Irritable Bowel Syndrome: Focus on Rifaximin and Eluxadoline

Pharmacotherapy. 2016 Mar;36(3):300-16. doi: 10.1002/phar.1712. Epub 2016 Mar 11.

Abstract

Diarrhea-predominant irritable bowel syndrome (IBS-D) is one of the most common diagnoses made by gastroenterologists. Current pharmacologic treatments for IBS-D include fiber supplements, antidiarrheal over-the-counter medications, probiotics, antispasmodics, antidepressants, and a 5-hydroxytryptophan 3 receptor antagonist. All of these options have limited efficacy in managing IBS-D. Rifaximin, a nonabsorbable antibiotic, has been evaluated in patients with IBS-D. In two randomized, double-blind, placebo-controlled phase III trials evaluating rifaximin 550 mg by mouth 3 times/day for 14 days, the primary efficacy end point was achieved by 9% more patients randomized to the rifaximin group compared with placebo (40.7% vs 31.7%, p<0.001, number needed to treat ~11). The primary efficacy end point was defined as the proportion of patients having adequate relief of global IBS symptoms for at least 2 of the 4 weeks during the primary follow-up period (weeks 3-6). In the phase III trial examining the efficacy and safety of repeated courses of rifaximin in patients who responded to the initial 2-week course, rifaximin given for up to two additional courses provided a statistically significant incremental benefit (33% vs 25%, p=0.02). Eluxadoline is a gut-targeting μ and κ opioid receptor agonist and a δ opioid receptor antagonist. The dual mechanism of eluxadoline may explain the antidiarrheal and abdominal pain-modulating properties and lack of profound constipation. In two identically designed randomized, double-blind, placebo-controlled phase III studies, 10.3% more patients in an eluxadoline 100 mg by mouth twice/day group met the primary efficacy end point during the follow-up 1-12 week period compared with placebo (p<0.001). The primary efficacy end point was a composite response, defined as improvement in worst abdominal pain and stool consistency at the same time on most (50% or more) days during the follow-up period. This review evaluates evidence for the use of rifaximin and eluxadoline in patients with IBS-D. Rifaximin provides an additional modality for the management of IBS-D patients; it has mild to moderate efficacy similar to other currently available treatment options. Rifaximin is relatively safe, lacks significant drug-drug interactions, and can be used for up to two additional retreatment courses. This may make rifaximin a possible initial or second-line treatment option. Eluxadoline can also offer relief to patients with IBS-D. While effective, because of several limitations, including drug-drug interactions and drug disease contraindications, as well as current lack of clinical experience, it may be tried as a second- or third-line agent.

Keywords: diarrhea; eluxadoline; irritable bowel syndrome; rifaximin.

Publication types

  • Review

MeSH terms

  • Administration, Oral
  • Diarrhea / drug therapy*
  • Diarrhea / etiology
  • Disease Management*
  • Gastrointestinal Agents / administration & dosage
  • Gastrointestinal Agents / therapeutic use*
  • Humans
  • Imidazoles / administration & dosage
  • Imidazoles / therapeutic use*
  • Irritable Bowel Syndrome / complications
  • Irritable Bowel Syndrome / drug therapy*
  • Phenylalanine / administration & dosage
  • Phenylalanine / analogs & derivatives*
  • Phenylalanine / therapeutic use
  • Randomized Controlled Trials as Topic
  • Rifamycins / administration & dosage
  • Rifamycins / therapeutic use*
  • Rifaximin

Substances

  • Gastrointestinal Agents
  • Imidazoles
  • Rifamycins
  • eluxadoline
  • Phenylalanine
  • Rifaximin