Irritable Bowel Syndrome: Current Mainstream Healthcare Viewpoint
Irritable bowel syndrome (IBS) affects 7-10% of the worldwide population, is significantly more common in women than men, and can have detrimental impact on a person's quality of life. Significant discoveries and changes have emerged during the past few years in regards to diagnosis, classification, and treatment of IBS.
What is IBS? After systematic review of the recent literature, a panel of IBS experts met to update and revise the IBS guidelines. The diagnostic criteria for IBS underwent multiple revisions, and the Rome III criteria are the current standard and defines IBS as recurrent abdominal pain or discomfort occurring at least 3 days per month in the last 3 months associated with 2 or more of the following criteria: a) Improvement in pain/discomfort with defecation, b) Onset of pain/discomfort associated with a change in stool frequency, and c) Onset of pain/discomfort associated with a change in stool consistency. In addition, symptom onset must be at least 6 months prior to diagnosis.
Subtyping of IBS has been modified to recognize the importance of a predominant stool pattern with 4 categories: 1) IBS with predominant diarrhea (IBS-D), 2) IBS with predominant constipation (IBS-C), 3) IBS mixed subtype (IBS-M), and 4) IBS undefined (IBS-U).
Treatment for IBS includes non-pharmacologic and pharmacologic agents. Tegaserod (Zelnorm) was found to improve significantly the symptoms of IBS, but it was withdrawn from the market in 2007 after postmarketing analyses showed a small but significant increase in cardiovascular events. However, Tegaserod is still available through an investigational drug program.
Antidepressants have long been used to treat the pain component of IBS. Numerous trials showed significant improvements in global IBS symptoms for patients receiving antidepressants compared with placebo. Tricyclic antidepressants (TCAs) have anticholinergic effects, i.e. constipating, and are thus more useful in patients with IBS-D, while the prokinetic selective serotonin reuptake inhibitors (SSRIs) may work better in patients with IBS-C.
Two antibiotics have been tested in randomized controlled trials: neomycin and rifaximin. Some patients in these trials reported symptomatic improvements, but neither drug is FDA approved for treating IBS. The IBS task force stated it could not make recommendations regarding continuous or intermittent use given the risks of drug-induced side effects and bacterial resistance.
Lubiprostone (Amitiza) is the only selective chloride channel activator currently available and is a gastrointestinal motility enhancer, which provided significant clinical benefits in randomized controlled trials. Thus, the FDA subsequently approved lubiprostone for the treatment of IBS-C in women.
There is limited data that suggest peppermint oil may improve IBS symptoms by relaxing smooth muscles. Psyllium (ispaghula husk) has received a conditional recommendation, with studies reporting global symptom improvement. Most trials of antispasmodic agents have been small and of poor methodologic quality, and current efficacy data most strongly support the use of hyoscine for treating IBS symptoms. Loperamide (Imodium) is an over-the-counter antidiarrheal, which decreases stool frequency and improves stool consistency.
Nonpharmacologic treatments include psychological therapies, such as cognitive behavioral therapy, hypnotherapy, and dynamic psychotherapy, which are more effective than standard therapy in relieving global IBS symptoms. However, relaxation therapy offered no significant benefit compared with standard therapy.
Probiotics demonstrate some efficacy for improving IBS symptoms. Symptom exacerbations after eating are common in IBS, and thus there has been significant attention given to nutrition and dietary modification. However, a recent randomized controlled trial looked at the efficacy of a food elimination diet, but no differences in symptom responses were identified. In fact, there is very little evidence to support modification of a patient's diet unless there is concern for gluten or lactose intolerance. At this time, there are insufficent data to comment on the efficacy of alternative therapies of Chinese herbal mixtures and acupuncture in the treatment of IBS.
Tobey Leung, M.D.