An Antiemetic for Irritable Bowel Syndrome?

A drug used for cancer patients may provide some relief to patients with IBS.

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Consider prescribing ondansetron (up to 24 mg/d) for patients who have irritable bowel syndrome with diarrhea (IBS-D).1

B: Based on a well-done double-blind, placebo-controlled randomized controlled trial (RCT).1

A 23-year-old woman who was ­diagnosed with irritable bowel syndrome (IBS) comes to your clinic with complaints of increased frequency of defecation with watery stools and generalized, cramping abdominal pain. She also notes increased passage of mucus and a sensation of incomplete evacuation.

She says the only thing that relieves her pain is defecation. She has tried loperamide, acetaminophen, and ibuprofen without relief. She does not have Crohn disease or ulcerative colitis. What else can you offer her that is safe and effective?

IBS is a chronic, episodic functional gastrointestinal disorder characterized by abdominal pain or discomfort and altered bowel habits: constipation (IBS-C), diarrhea (IBS-D), or alternating periods of both—mixed (IBS-M).2 The diagnosis is based on Rome III criteria, which include recurrent abdominal pain or discomfort on at least three days per month in the past three months associated with two or more of the following: improvement with defecation, onset associated with a change in frequency of stool, and onset associated with a change in form (appearance) of stool.3 IBS often is unrecognized or untreated, and as few as 25% of patients with IBS seek care.4

IBS-D affects approximately 5% of the general population in North America.5,6 IBS-D is associated with a considerably decreased quality of life and is a common cause of work absenteeism.7,8 Because many conditions can cause diarrhea, patients typically undergo numerous tests before receiving an accurate diagnosis, which creates a financial burden.9

For many patients, current IBS treatments—including fiber supplements, laxatives, antidiarrheal medications, antispasmodics, and antidepressants such as tricyclics and selective serotonin reuptake inhibitors—are unsatisfactory.10 Alosetron, a 5-hydroxytryptamine 3 (5-HT3) receptor antagonist, has been used to treat IBS-D,11 but this medication was voluntarily withdrawn from the US market in 2000 due to concerns about ischemic colitis and severe constipation.12 It was reintroduced in 2002 but can be prescribed only by clinicians who enroll in a prescribing program provided by the manufacturer, and there are restrictions on its use.

Ondansetron—another 5-HT3 receptor antagonist used to treat nausea and vomiting caused by chemotherapy—may be another option for treating IBS-D. Garsed et al1 recently conducted an RCT to evaluate the efficacy of ondansetron for patients with IBS-D.

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