A large proportion of patients with abdominal pain related to irritable bowel syndrome with diarrhea (IBS-D) who were treated with rifaximin experienced clinically meaningful improvement in pain, regardless of baseline pain severity and whether this was their first treatment course or a repeat treatment, according to a study published in Gastroenterology. Furthermore, baseline pain levels before repeat treatment courses were significantly reduced compared with baseline pain before initial treatment course.

In adults, Rifaximin is indicated for the treatment of IBS-D. This post hoc analysis of a phase 3 clinical trial assessed the response of adult participants with IBSD (≥3 mean daily abdominal pain score) to rifaximin 550 mg 3 times daily. Participants were given a 2-week treatment course, with daily abdominal pain assessments (score range, 0-10), followed by a 4-week evaluation period after completion of treatment. Participants who responded to rifaximin treatment and then had symptoms recur up to 22 weeks post-treatment were given a repeat 2-week course rifaximin followed by another 4-week evaluation period. Treatment response was defined as a ≥30% decrease from mean baseline weekly abdominal pain score and a composite endpoint of ≥50% decrease from baseline days per week with mushy/watery stool (Bristol Stool Scale type 6/7) for ≥2 of the first 4 weeks post-treatment. Participants (N=2579) were divided into subgroups according to baseline pain level scores: <5.0 (group A), ≥5.0 to <8.0 (group B), and ≥8.0 (group C).

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Of the 2438 participants available for efficacy analysis (group A, n=962; group B, n=1260; group C, n=216), rifaximin response (composite endpoint) was seen in 40.4% of group A, 47.0% of group B, and 43.1% of group C, and treatment response for individual pain improvement was seen in 57.0% of group A, 57.9% of group B, and 49.5% of group C. Among the 328 participants whose symptoms recurred (group A, n=114; group B, n=178; group C, n=36), median abdominal pain scores at the repeat treatment baseline was 4.4 points (mean, 4.6) lower than scores at the initial baseline. When repeat treatment participants were subgrouped by new baseline pain scores, treatment response to the second 2-week rifaximin treatment course for abdominal pain was 57.9% for group A, 50.6% for group B, and 50.0% for group C, and composite end point treatment response was 38.6%, 34.8%, and 27.8%, respectively.


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Study investigators conclude that rifaximin treatment resulted in meaningful pain improvements of abdominal pain in a high percentage of patients, irrespective of baseline severity category and treatment course. This supports the efficacy of this medication for the treatment of IBSD-related abdominal pain.

Reference

Lembo A, Heimanson Z, Cash BD. Characterization of abdominal pain response to rifaximin in patients with irritable bowel syndrome with diarrhea (IBSD), by baseline pain severity. Gastroenterology. 2019;156(6): S0016-5085(19)38889-4.