Rifaximin-Alpha Increases Lactase Activity in Patients with Irritable Bowel Syndrome Without Constipation and Small Intestinal Bacterial Overgrowth.

Background: Irritable bowel syndrome symptoms are associated with diverse pathophysiological mechanisms including small intestinal bacterial overgrowth and food intolerance. Small intestinal bacterial overgrowth leads to the decreased activity of several digestive enzymes, including lactase.

Aims: To assess the efficacy of rifaximin-alpha on the symptoms and lactase activity of patients with irritable bowel syndrome without constipation.

Methods: This was a prospective, pilot study. The recruited patients had irritable bowel syndrome without constipation (Rome IV criteria), a positive lactulose-Hydrogen Breath Test for small intestinal bacterial overgrowth, low urinary D-Xylose levels measured using the Lactest® test, and self-reported lactose intolerance. In addition, lactose HBT was performed. All patients received 400 mg rifaximin-alpha every 8 h for 2 weeks. Four weeks after the intervention, lactose and lactulose HBT were performed, and the symptoms and urinary D-Xylose levels were evaluated.

Results: After treatment with rifaximin-alpha, 60% of the patients reported improvement in abdominal pain, 44% in bloating, 36% in flatulence, 60% in borborygmi, and 72% in stool consistency. A negative lactulose-Hydrogen Breath Test result for SIBO was documented in 32% of patients, and lactose maldigestion by lactose-Hydrogen Breath Test was reduced from 88 to 52% of the studied subjects. The median D-Xylose levels before and after treatment were 7.6 (IQR 4.34-13.7) mg/dL vs. 10.4 (IQR 7.1-17.3) mg/dL, p = 0.002.

Conclusions: Rifaximin-alpha caused symptomatic improvement, reduced lactose maldigestion, and reduced positive Hydrogen Breath Test results for small intestinal bacterial overgrowth in patients with irritable bowel syndrome without constipation.