Ondansetron Relieves Irritable Bowel Syndrome Symptoms

Patients with irritable bowel syndrome with diarrhea (IBS-D) suffer not only the pain and discomfort of frequent loose stools, but fear of incontinence. For many patients, that results in panic and anxiety.

In an effort to address those concerns, a team at Nottingham Diseases Centre, University Hospital, Nottingham, UK, conducted a study of ondansetron vs. placebo in a group of 120 IBS-D patients. The group taking ondansetron (a widely available generic) got significant relief from their debilitating symptoms, Klara Garsed and colleagues reported in Gut .

Compared with placebo, ondansetron “significantly improved stool consistency, patients experienced fewer days with urgency, less frequent defecation, and less bloating. Pain associated with IBS-D did not change significantly.

Overall, 65% of patients reported symptom relief with ondansetron, while only 14% getting the placebo reported relief.

In the crossover study, participants received 5 weeks of oral placebo treatment and 5 weeks of ondansetron 4 mg tablets with a 2-3 week washout period in between each treatment period.

Loperamide was allowed as a rescue medication but needed to be discontinued for the final 2 weeks of the period. Patients kept track of their symptoms with daily diaries.

The team also measured gut transit times in the participants, and found ondansetron significantly slowed those times.

The only adverse event was constipation, which occurred in 9% of the patients taking ondansetron, but most of those patients found that was corrected when their dosage was reduced.

The researchers concluded that “patients with IBS-D have a clear preference for ondansetron compared with placebo, even though it did not alter the number of days with pain, suggesting that for these patients it was urgency and loose stools which were the most troublesome symptoms.”

Animal studies suggest that ondansetron taken at higher doses might also relieve pain, they wrote, though that would also likely increase the incidence of constipation.

The small size of the study did not assess safety, the authors wrote, but ondansetron has been used safely to treat nausea for 25 years.