Irritable bowel syndrome guidance

There is only limited evidence on which to base treatment decisions in irritable bowel syndrome (IBS). For more information see NICE CG61

Diagnosis and Referral

Irritable Bowel Syndrome symptoms may vary

  1. Alternating bowel habit – most common
  2. Pain predominant
  3. Constipation predominant
  4. Diarrhoea predominant - least common

Note, the above may also be alarm symptoms of gastrointestinal cancers and inflammatory bowel disease.

No diagnostic test for IBS exists as yet. NICE provide guidance on making a diagnosis.

Please see Irritable Bowel Syndrome (IBS) CRG for further details

Refer to secondary care for further investigation if any of the following 'red flag' indicators are present:

  • unintentional and unexplained weight loss
  • rectal bleeding
  • a family history of bowel or ovarian cancer
  • a change in bowel habit to looser and/or more frequent stools persisting for more than 6 weeks in persons aged over 60 years
  • anaemia
  • abdominal or rectal mass
  • inflammatory markers for inflammatory bowel disease

General Management Advice

Explanation and reassurance

  • Explanation of the nature of IBS thereby addressing specific concerns.

Recognising possible causal factors / differential diagnosis

  • Post infective, e.g. after gastroenteritis.
  • 'Stress', e.g. bereavement, interpersonal relationships.
  • Inflammatory bowel disease.

Dietary and lifestyle adjustments (for more information see NICE CG61)

  • Patients with IBS should be discouraged from eating insoluble fibre (e.g. bran). If an increase in dietary fibre is advised, it should be soluble fibre (e.g. ispaghula powder) or foods high in soluble fibre (e.g. oats).
  • An individual approach to diet is required. Dietary advice is provided with NICE guidance on IBS.
  • Some food may exacerbate symptoms in some patients, e.g. beer and coffee, citrus fruit, high fat food and wheat products.
  • Some food may help symptoms, e.g. mint tea.
  • Consider referral for a trial low FODMAP diet (specialist dietetic input)

Aloe vera

  • The use of Aloe vera in treatment of IBS should be discouraged. Aloe vera has been shown to be of no benefit in IBS compared to placebo. Potentially serious adverse effects are associated with Aloe vera preparations including an increase in risk of dehydration and electrolyte imbalance when taken with laxative drugs, lowering of potassium levels and possible lowering of blood sugar.

Symptom management

Pain and spasm


Avoid lactulose in patients with IBS.

  • Ispaghula husk sachet, For people who cannot tolerate bulk laxatives or require an additional laxatives consider:
  • Macrogol Compound oral powder sachets, Usually 1 sachet once or twice daily in 125ml water
  • Senna, 2-4 tablets at night (short-term use only)

See section 1.6 Laxatives


People with IBS should be advised how to adjust their doses of laxative or antimotility agent according to the clinical response. The dose should be titrated according to stool consistency, with the aim of achieving a soft, well-formed stool (corresponding to Bristol Stool Form Scale type 4).


Antidepressants are not licensed for use in IBS and should only be used if laxatives, loperamide or antispasmodics have not helped.

  • Amitriptyline (unlicensed indication), Should be considered the first choice TCA due to its low acquisition cost
  • Imipramine (unlicensed indication), less sedating than amitriptyline and should be considered if sedation proves a problem with amitriptyline
  • Fluoxetine (unlicensed indication), Should be considered if TCAs prove ineffective

See section 4.3 Antidepressant drugs


  1. Tricyclic antidepressants – treatment should start at a low dose, 5-10mg of amitriptyline to be taken once at night. The dose may be increased to a maximum of 30mg.
  2. SSRIs should be considered for patients with IBS only if tricyclics antidepressants have been shown to be ineffective. SSRIs are particularly useful for patients with IBS with constipation. The maximum dose of fluoxetine is 20mg once daily.
  3. Prescribers should take into account the possible adverse effects when prescribing tricyclic antidepressants or SSRIs. Patients taking tricyclics antidepressants or SSRIs should be followed-up after 4 weeks and then at 6-12 monthly intervals. Prescribers should be aware that adverse effects may occur sooner than efficacy is observed.


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