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Treatments for Irritable Bowel Syndrome

Search and inclusions

Irritable bowel syndrome (IBS) is said to affect about 1 in 5 women and 1 in 10 men, and be a major reason for visits to GPs and gastroenterologists. For all this, there is a surprising lack of effective treatments, and textbooks are often surprisingly unhelpful. A new systematic review [1] may not provide all the answers, but it turns an impenetrable fog into a heavy mist, and gives some clues for patients and their carers.

Search and inclusions

Comprehensive searching of four databases, including the Cochrane Library was supplemented by manual searches of bibliographies, but only for English language reports. For inclusions a trial had to satisfy six criteria:

A qualitative assessment of the validity of trials was done, and high quality studies were assessed separately.


There were 70 studies found, of which 28 were judged to be of high quality/validity. It was not possible to combine information, and vote counting was used. For the high quality studies the results are shown in the Table.

Table: High quality trials in IBS

Treatment High quality trials (positive/total) Number of patients Comment
Bulking agents 3/7 341 Possible positive effects from ispaghula husk, but only one of the three positive studies was of sensible size
Smooth muscle relaxants 7/7 701 Consistent improvement in abdominal pain, with NNTs reported from individual trials between 1.6 and 6.7, but no overall value because five different drugs studied. Including lower quality studies, 13 of 16 were beneficial.
Prokinetic agents 1/4 266 No evidence of any benefit
Loperamide 2/2 100 Both studies had improvement in diarrhoea, including frequency of bowel movements, but not abdominal pain or distention
5HT receptor antagonists 2/2 420 Both studies showed global improvements and improvements for some symptoms. Constipation a common adverse effect in one large study of alosetron
Chinese herbal medicine 1/1 116 Global improvement
Peppermint oil 1/1 110 Improvement in symptoms of abdominal pain, distention, stool frequency
Amitriptyline 1/1 14 Trivial data

Only three interventions had a high proportion of positive trials (minimum of two studies and 100 patients). Smooth muscle relaxants were consistently effective in reducing abdominal pain associated with IBS, with NNTs for individual trials in the range of 2 to 6. Loperamide was effective in treating diarrhoea associated with IBS. 5HT receptor antagonists appeared to be effective both in terms of global improvement and some individual symptoms, though at the cost of a degree of constipation perhaps.


There does seem precious little to say about effective treatments for such a common and often distressing condition. But there are some clear indications about what doesn't work or where there is no evidence. Rumours abound about new treatments for IBS making their appearance in the next few years, and at least we know where we start from. The paper also comments on length of follow-up for high-quality trials - twelve weeks. It is interesting that there was only a single small trial for amitriptyline, and that other favoured treatments were supported by no high-quality trials. Make one think.


  1. J Jailwala, TF Imperiale, K Kroenke. Pharmacologic treatment of the irritable bowel syndrome: a systematic review of randomized, controlled trials. Annals of Internal Medicine 2000 13: 136-147.
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