Tegaserod (Zelnorm) for irritable bowel syndrome: reports of serious diarrhea and intestinal ischemia

Reason for posting: The serotonin 5-HT₄ receptor partial tegaserod (Zelnorm) is sometimes prescribed for patients who have irritable bowel syndrome with constipation.1 However, a recent letter to health care professionals from the drug's manufacturer warns of serious adverse events in some cases.2 Although 1 in 10 patients taking the drug will experience mild diarrhea, about 1 in 250 will have very serious diarrhea complicated by hypovolemia, hypotension and syncope that sometimes necessitates admission to hospital and intravenous therapy.2 As well, ischemic colitis and other forms of intestinal ischemia have occurred in some patients taking the drug; although the exact incidence of this adverse event is unknown, it probably occurs in fewer than 1 in 11 000 patients.2

The drug: The pathophysiology of irritable bowel syndrome is not well understood, but serotonin 5-HT₄ receptors appear to mediate peristalsis in the enteric nervous system.3 Tegaserod is a serotonin 5-HT₄ receptor antagonist that reduces symptoms of abdominal pain, discomfort, bloating and constipation. A recent Cochrane review concluded that the number needed to treat to reduce these gastrointestinal symptoms (relative to placebo) is 17.1

What to do: Irritable bowel syndrome is a common, chronic, painful and frustrating condition for many patients4 but is itself not life-threatening. Most patients do not require drug treatment but instead benefit from “listening, validating, educating, and identifying and reinforcing coping strategies in a long-term therapeutic alliance.”4 For affected patients with constipation, fibre supplementation or periodic use of osmotic laxatives is often the best treatment.3 Tegaserod therapy should be reserved for specific patients (women with irritable bowel syndrome and constipation) who have more moderate to severe symptoms.3 The duration of treatment should not exceed 12 weeks, and therapy should be stopped after 4 weeks if there has been no response.2 Patients should be warned that they may experience potentially serious diarrhea or, rarely, intestinal ischemia. They should be advised to seek prompt medical attention if serious diarrhea, lightheadedness or postural symptoms develop during treatment. The drug should be immediately stopped if rectal bleeding or new or worsening abdominal pain develops.

Eric Wooltorton CMAJ