Introduction

A Task Force composed of 10 eminent US gastroenterologists was charged by the American College of Gastroenterology with reviewing the different treatments for irritable bowel syndrome (IBS), and reporting which ones they considered effective.¹ This is a summary of their main findings.

What they did

All the published clinical studies on IBS treatments were reviewed, and those meeting certain standards were selected for further analysis. The Task Force used several grades of evidence, which they classified into Levels I through V. Only Levels I and II (randomized controlled clinical trials - 'adequate' and 'less-adequate') were considered to provide sufficient evidence of effectiveness.

Treatment of IBS should be started if the patient and her doctor believe the symptoms lessen the patient's quality-of-life. The Task Force recommended that IBS patients be classified as either:

• IBS with abdominal discomfort and bloating, with alternating diarrhea and constipation;
• IBS associated with abdominal discomfort, bloating, and constipation;
• IBS associated with abdominal discomfort, urgency to defecate, and diarrhea.

The Task Force analyzed the available clinical information for the following treatments: antispasmodic drugs, bulking agents (like fiber), loperamide, antidepressants, tegaserod, aldosetron, and behavioral therapy.

What they recommended

Antispasmodic agents (hyoscyamine and dicyclomine are those available in the USA): Only one of three studies meeting the required standards showed a significant improvement in IBS symptoms, compared with the controls (who received placebo, or dummy pills). The other two studies showed no difference in the effectiveness of the antispasmodic drug and placebo. At high doses, antispasmodic drugs may produce side-effects like dry mouth, dizziness, blurred vision, and constipation. "Not recommended."

Bulking agents (e.g .wheat bran, corn fiber, calcium polycarbophil, psyllium): None of the 13 trials analyzed were considered 'adequate' (i.e. Level I or II evidence), and there were only slight indications of fiber's benefits on IBS symptoms. The Task Force concluded, "Fiber is appropriate for treatment of constipation, but may not be recommended for treatment of IBS".

Loperamide (an antidiarrheal drug): Three adequate studies examined the use of loperamide in IBS patients with diarrhea; in general, stool frequency and stool consistency were improved, but bloating and abdominal pain were unaffected. "Not recommended."

Antidepressants: The older tricyclic antidepressants, like amitriptyline and desipramine, were analyzed in 6 not-very-adequate studies; they were found to be no more effective than placebo at relieving all IBS symptoms, but they did improve abdominal pain. The selective serotonin reuptake inhibitors [SSRIs], such as Prozac or Zoloft, have not yet been studied adequately in IBS patients. "Not recommended."

Tegaserod This new drug was described by the Task Force as being more effective than placebo in relieving the symptoms of constipation-predominant IBS in women. This recommendation was based on 4 high-quality 12-week clinical studies. Diarrhea was the commonest side effect. Although over 80% of the people in the studies were women, and the FDA's approval of the drug is limited to women, the men in the trials reported significant benefits. "Recommended."

Alosetron (5HT3 receptor antagonist): This drug is effective in treating symptoms in women with IBS that is associated with diarrhea. As with tegaserod, it's effectiveness has been shown in 4 high-quality studies. After approval in the USA, marketing of the drug was halted in 2000 because of reports in some patients of a serious side effect called ischemic colitis. The FDA allowed marketing to resume in June 2002 for treating "women with severe, diarrhea-predominant IBS who have failed to respond to conventional IBS therapy". Constipation is the most common side event, and patients should stop taking the drug, at least temporarily, if this is severe. "Recommended."

Behavioral therapy: Behavioral approaches for treating IBS that were analyzed by the Task Force included relaxation therapy to reduce stress, biofeedback regulation of bowel habits, hypnotherapy aimed at controlling intestinal muscle contractions, cognitive therapy, and psychotherapy. The 16 studies evaluated were considered to be of intermediate quality only. In 11 of them, IBS symptoms were significantly improved, compared with those in control (untreated) patients; in 5 studies, there were no significant improvements. Most (80%) of the patients included in the studies had psychological disorders along with their IBS. "Recommended."

What does this mean?

The Task Force assessment represented a 'snapshot'- at any one time, there are some accepted, traditional therapies for which there may not be good evidence of effectiveness, some treatments with proven effectiveness, and some treatments that haven't yet been studied fully. The Task Force recognized this, but felt it could only recommend treatments for which there was good evidence.

They only found high-quality Level I evidence, for or against effectiveness, from studies sponsored by the manufacturers of the two drugs they judged effective - tegaserod and alosetron. It is unlikely that such rigorous studies will ever be done for any of the older, or non-drug treatments such as fiber supplements.

The conclusions of the Task Force were that only the two drugs in question, as well as behavioral therapy, had sufficient positive evidence to allow them to be recommended for use in treating IBS. This represents a much narrower viewpoint than that put forward in a recent Lancet review, which we recently summarized on this site (see first link below).