ACG/UEGW 2016 News in Gastroenterology: IBS-D

ACG 2016. P346. Improvements Over Time in Individual Diarrhea-Predominant Irritable Bowel Syndrome Symptoms (IBS-D) with Rifaximin Repeat Treatment
Mark Pimentel, MD1, Anthony J. Lembo, MD2, Ray Wolf, PharmD3
1. Cedars-Sinai Medical Center, Los Angeles, CA; 2. Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA; 3. Salix Pharmaceuticals, Raleigh, NC

Results: Baseline symptom scores for abdominal pain, stool consistency (Bristol Stool Scale, type 6 or 7), IBS-related bloating, fecal urgency, daily IBS symptom score, and bowel movement frequency were similar for the placebo and rifaximin groups. Symptom improvement was observed throughout the double-blind period with placebo and rifaximin. After the first rifaximin retreatment, mean changes from baseline observed over time ranged from -0.63 to -1.48 for abdominal pain, -1.30 to -1.96 for stool consistency (loose/watery stools), -0.39 to -0.97 for IBS-related bloating, -0.81 to -1.69 for fecal urgency, -0.41 to -0.97 for daily IBS symptom score, and -0.22 to -0.64 for bowel movement frequency. Overall, improvement of symptoms tended to be greater with rifaximin than placebo at most weeks throughout the double-blind period. At initiation of the second retreatment course of rifaximin, symptoms again improved in both treatment groups versus baseline. Symptoms continued to show incremental improvement versus baseline through 4 weeks after the second rifaximin repeat retreatment course: significantly larger improvements from baseline in abdominal pain (P < 0.0001), daily IBS symptoms (P=0.01), fecal urgency (P=0.005), and bowel movement frequency (P=0.01) were seen with rifaximin versus placebo 4 weeks after completion of the second rifaximin retreatment course.

Discussion: In patients with IBS-D who experienced recurrent symptoms, additional courses (up to 2 repeat treatments) of rifaximin continued to improve individual IBS symptoms over time.

CARE Faculty Perspective: Rifaximin is a non-systemic antibiotic used for patients suffering from IBS-D. This analysis evaluated the effect of up to 2 repeat rifaximin courses on individual IBS-D symptoms, and found that it continued to improve symptoms over time. However, since IBS is a chronic illness, the effect of longer-term repeat courses of antibiotic use on the durability of the treatment outcome and gut microbiome remains to be determined.  Rifaximin is currently under Health Canada review for the treatment of IBS-D.