Effects of a 5-HT(3) antagonist, ondansetron, on fasting and postprandial small bowel water content assessed by magnetic resonance imaging

Aliment Pharmacol Ther. 2010 Sep;32(5):655-63. doi: 10.1111/j.1365-2036.2010.04395.x.


Background: 5-HT(3) antagonists have been shown to be effective in relieving the symptoms of irritable bowel syndrome with diarrhoea (IBS-D). Using a recently validated magnetic resonance imaging (MRI) method, we have demonstrated reduced fasting small bowel water content (SBWC) in IBS-D associated with accelerated small bowel transit. We hypothesized that slowing of transit with ondansetron would lead to an increase in SBWC by inhibiting fasting motility.

Aim: To assess the effects of ondansetron compared with placebo in healthy volunteers on SBWC and motility in two different groups of subjects, one studied using MRI and another using manometry.

Methods: Healthy volunteers were given either a placebo or ondansetron on the day prior to and on the study day. Sixteen volunteers underwent baseline fasting and postprandial MRI scans for 270 min. In a second study, a separate group of n = 18 volunteers were intubated and overnight migrating motor complex (MMC) recorded. Baseline MRI scans were carried out after the tube was removed.

Results: Fasting SBWC was markedly increased by ondansetron (P < 0.0007). Ondansetron reduced the overall antroduodenal Motility Index (P < 0.04). The subjects who were intubated had significantly lower fasting SBWC (P < 0.0002) compared with the group of subjects who were not intubated.

Conclusions: The 5-HT(3) receptor antagonism increased fasting small bowel water. This was associated with reduced fasting antroduodenal Motility Index which may explain the clinical benefit of such drugs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Diarrhea / drug therapy*
  • Fasting
  • Female
  • Humans
  • Irritable Bowel Syndrome / drug therapy*
  • Magnetic Resonance Imaging
  • Male
  • Manometry
  • Middle Aged
  • Ondansetron / therapeutic use*
  • Postprandial Period
  • Serotonin Antagonists / therapeutic use*
  • Treatment Outcome
  • Young Adult


  • Serotonin Antagonists
  • Ondansetron