Because IBS is a chronic disorder that may be exacerbated by a number of factors, successful treatment requires a multicomponent, long-term approach.

Non-pharmacological management

Avoidance of dietary excesses, caffeine, known food triggers, excess fruit/sorbitol intake, excess fat intake and flatulence-causing foods is widely recommended. However, the efficacy of specific diets or elimination diets is undetermined.(Mertz 2003)

Enough rest and exercise are important.
The use of bran is questionable. Bulking agents appear to be more helpful.

A variety of psychotherapy techniques appear to specifically improve the symptoms of diarrhoea and abdominal pain in some patients with IBS. Patients with co-existing anxiety or depression have a better outcome with psychotherapy than do patients without these conditions. Psychotherapy is thus considered useful for selected patients who have prominent psychosocial issues.(Mertz 2003)

However, on the basis that the underlying problem in IBS involves excess contraction of smooth muscle in the gut wall, it is rational to use drugs to relieve the spasm.

Antispasmodic agents

Antispasmodic agents relax the smooth muscle of the gut or reduce contractility, and are thought to decrease global symptoms of IBS and abdominal pain. Indeed a recent meta-analysis showed that myorelaxants, such as mebeverine, were significantly better than placebo in effecting global improvement of IBS symptoms.(Poynard, Regimbeau et al. 2001) However, another meta-analysis suggest that some antispasmodic agents may be more effective in alleviating pain than the symptoms of diarrhoea.(Jailwala, Imperiale et al. 2000)

The antispasmodics which are available – the so-called musculotropic antispasmodics - which act directly on the smooth muscle cells relieve intestinal spasms but do not have the anticholinergic side-effects. They include the Solvay products Duspatal®, Duspatalin®, Colofac® (mebeverine) and Dicetel®, Eldicet® (pinaverium bromide).

Non-specific bowel-directed therapy

Antidiarrhoeal agents are employed to minimize the inconvenience and discomfort of diarrhoea, but these agents were not specifically developed to treat IBS, are recommended for short term use, and may not be effective for pain.(Jailwala, Imperiale et al. 2000; Mertz 2003; Mach 2004)

Opiate/opioid analogues probably act both centrally and peripherally to decrease intestinal motility. The three main opioids used in the treatment of diarrhoea are codeine phosphate, diphenoxylate and loperamide.(Gattuso and Kamm 1994; Mertz 2003)All three drugs share the range of opioid adverse effects, although there are qualitative and quantitative differences. The most common are nausea, vomiting, drowsiness, and constipation.(Gattuso and Kamm 1994)

Other agents used in the treatment of IBS include: antibiotics, administered for small-bowel bacterial overgrowth; herbal remedies, which have been found to offer no relief of symptoms; and peppermint oil, believed to have antispasmodic properties but which has achieved mixed results.(Mertz 2003)

Psychotropic agents

Tricyclic antidepressants (TCAs) have been used in low doses for their pain-reducing qualities; these agents may exert an effect by reducing the sensitivity of peripheral nerves or by causing alterations in the brain.(Mertz 2003) Although these agents apparently show some efficacy in IBS with diarrhoea predominance, IBS is not an indication for TCAs, and the well-known side effects of TCAs restrict their use.

Anticholinergics are also used to relieve pain

5-HT3 receptor antagonists

5-HT3 receptor antagonists are particularly effective for the treatment of IBS with diarrhoea predominance. They are not discussed in this section.

5-HT4 receptor agonists

5-HT4 receptor agonists are effective for the treatment of IBS with constipation predominance and are not discussed in this section