Patients with diarrhea-predominant irritable bowel syndrome who had a positive baseline result from a lactulose breath test were more likely to respond to Xifaxan therapy, according to results of open-label study.
Ali Rezaie, MD, medical director of the GI motility program at Cedars-Sinai Medical Center, and colleagues wrote that like other IBS therapies, Xifaxan (rifaximin, Salix) can be effective, but the ability to determine response is limited.
“One goal of therapy should be a tailored approach to the management of IBS,” they wrote. “A goal of maximizing symptom improvement would be highly valued, as this can potentially decrease direct and indirect health care costs.”
To assess the ability of the lactulose breath test (LBT) to predict response to rifaximin therapy, researchers conducted an open-label study comprising 93 patients with IBS-D. Patients received rifaximin three times a day for 2 weeks, followed by a 4-week assessment period after treatment. They underwent LBT before and after therapy.
Investigators assessed patient response — defined as at least 30% reduction in abdominal pain and at least 50% decrease in frequency of mushy or watery stool from baseline — and the relationship between clinical outcomes and LBT results.
Sixty-two patients had a positive baseline LBT result. Further, 45 patients responded to rifaximin therapy, of whom 37 had positive baseline LBT (59.7%) and 8 had a negative baseline LBT (25.8%; P = .002). Patients with a positive LBT at baseline also experienced greater improvement in several individual IBS symptoms, including abdominal pain, bloating and bowel movement frequency.
Although LBT results after therapy were not linked with clinical response, patients whose LBT results normalized after receiving rifaximin experienced the highest response rate (76.5%).
“Although breath testing is the strongest known predictor or response to rifaximin in patients with IBS-D, it did not predict response in all patients, suggesting that rifaximin may have another mechanism of action,” Rezaie and colleagues wrote. “This underscores the heterogeneity of IBS and the need to develop biomarkers that can help further stratify IBS subtypes based on the underlying pathophysiology.” – by Alex Young
Disclosures: Rezaie reports serving as a consultant for and receiving research grants from Salix and serving as a consultant for GutHub. He also reports having equity in Gemelli Biotech. Please see the full study for all other authors’ relevant financial disclosures.