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First drug to treat irritable bowel syndrome approved

The Food & Drug Administration recently approved tegaserod (Zelnorm, Novartis), the first drug for the short-term treatment of women with irritable bowel syndrome (IBS) whose primary bowel symptom is constipation. It is also the first agent in a new class of drugs.

Tegaserod is a 5-HT₄ receptor partial agonist, explained Walter Peterson, M.D., professor of medicine, University of Texas-Southwestern Medical Center, Dallas. It binds to the 5-HT₄ receptors in the gastrointestinal tract, triggering a peristaltic reflex in the gut and increasing bowel motility. In addition, he continued, tegaserod appears to have an effect on the afferent nerve pathway from the gut to the brain. "It is believed that patients with IBS have a hypersensitive gut, so to speak," he said. "This drug tends to blunt any stimuli going from the gut back to the brain."

The FDA originally wanted further analysis of safety data before approving tegaserod, according to Mark Pimentel, M.D., director, GI Motility Lab, Cedars-Sinai Medical Center, Los Angeles. Specifically, the agency was concerned about the increased number of cholecystectomies among patients treated with tegaserod compared with those treated with placebo. These concerns have been alleviated by revisiting the data, he said.

The safety and efficacy of tegaserod in men have not been established, cautioned Pimentel and Peterson, because the drug has not been studied in enough men to make any recommendations. The safety and efficacy of tegaserod have not been established in children either, and it should not be used in pediatric patients until further studies are available, Peterson said. Tegaserod appears safe to use in geriatric patients, however, said Peterson and Pimentel. No dosage adjustment appears necessary for use in older patients, according to the package insert (PI).

Tegaserod is classified as a pregnancy category B and should not be used in pregnant or lactating women until further data are available, Peterson said. Patients with diarrhea should not take tegaserod either, both Peterson and Pimentel added.

In clinical trials, said Peterson, diarrhea and headache occurred more frequently in those receiving tegaserod than in those receiving placebo. Diarrhea usually occurred within the first week or so of treatment and was usually transient, he said. The recommended dosage is 6 mg b.i.d. p.o. before meals. According to the PI, the recommended duration of therapy is four to six weeks. An additional four- to six-week course of treatment can be considered for patients who respond to therapy.

Peterson feels that R.Ph.s can play an important role by ensuring the appropriate patients are treated with tegaserod. "Pharmacists are best able to know, based on any other medications the patient is taking, what the diagnosis actually is," he explained. "Patients taking corticosteroids for inflammatory bowel disease, for example, should not be taking tegaserod." Pharmacists can also alert physicians regarding persons who seek frequent refills or who have their dose of tegaserod increased, yet claim their constipation has not improved.

Charlotte LoBuono

TIPS TO REMEMBER: Zelnorm

• Zelnorm has no known drug-drug interactions.

• Diarrhea, the most frequently occurring adverse effect, occurred within the first week of treatment during studies and typically resolved with continued therapy. Most patients experienced a single episode.

• Zelnorm is contraindicated in patients with severe renal impairment, moderate or severe hepatic impairment, a history of bowel obstruction, symptomatic gallbladder disease, suspected sphincter of Oddi dysfunction, or abdominal adhesions.

• Zelnorm should not be initiated in patients who are experiencing or frequently experience diarrhea. Zelnorm should be discontinued immediately in patients with new or sudden worsening of abdominal pain.

 

Charlotte LoBuono. First drug to treat irritable bowel syndrome approved. Drug Topics 2002;16:10.