On April 28, 2004, the FDA announced the addition of new risk information to the health professional labeling for Zelnorm (tegaserod maleate; Novartis Pharmaceuticals, East Hanover, NJ). This information includes a warning about diarrhea and a precaution regarding ischemic colitis.
The overall occurrence of diarrhea observed in clinical trials was 9% in the tegaserod group, compared with 4% in the control group. Diarrhea usually occurred early in treatment and resolved with continued therapy; only 1.6% of patients in clinical trials discontinued therapy because of diarrhea.Yet, a small percentage of patients (0.04%) experienced serious consequences of diarrhea, including hypovolemia, hypotension, and syncope, which very rarely led to hospitalization. Therapy should be discontinued if these events are observed.
Recent epidemiologic studies indicate that ischemic colitis, a rare condition in which blood flow to the colon is insufficient to meet its metabolic needs, occurs at a higher rate in patients with irritable bowel syndrome than in the general population. Postmarketing surveillance of patients who take tegaserod, however, has yielded rare reports of ischemic colitis. No cases of ischemic colitis were observed with tegaserod in any of the clinical trials, which involved more than 7000 patients; there is no evidence of a causal relationship between tegaserod use and ischemic colitis. Therapy should be discontinued and appropriate diagnostic tests conducted in patients who experience new or worsening abdominal pain or blood in the stool.