Pilot trial: Pregabalin on colonic sensorimotor functions in irritable bowel syndrome

Abstract

In prior studies, pregabalin reduced rectal or colonic pain in patients with irritable bowel syndrome and healthy adults, suggesting reduction of afferent function. To assess effects of pregabalin on colonic compliance, sensory and motor functions in patients with constipation-predominant irritable bowel syndrome. In a pilot, double-blind, placebo-controlled, parallel-group study, we tested oral pregabalin, 200mg, in 18 patients with constipation-predominant irritable bowel syndrome. With a barostatically controlled polyethylene balloon in the left colon, we assessed sensation thresholds and colonic compliance using ascending method of limits, sensation ratings over 4 levels of distension, fasting and postprandial colonic tone and phasic motility. Analysis of covariance (adjusted for the corresponding pre-drug response) was used to compare placebo and pregabalin. After 45% participants completed studies, we conducted an interim analysis to assess the conditional power to detect pre-specified treatment effects given the observed variation and treatment group differences based on the planned sample size for the trial. Pregabalin did not significantly affect colonic compliance, sensation thresholds, sensation ratings, fasting or postprandial tone or motility index. The study was stopped for futility to detect an effect on visceral pain with the planned design and sample size. Pregabalin, 200mg, might not reduce distension-related colonic pain in constipation-predominant irritable bowel syndrome patients.