IBS: The evidence for conventional pharmacological treatment

IBS is one of the most common disorders seen in primary care and gastroenterology specialty practice. Conventional medicine approaches consist of combinations of diet advise, psychological, and drug therapies.

Current conventional medicine guidelines make a number of recommendations for treatment [i],[ii]. However most of these are consensus-based and have inadequate clinical evidence for a strong recommendation. The summary of US guidelines notes, “Despite the large number of published studies, in most cases our recommendations are weak because either (1) the quality of the available data and/or (2) the balance of risks and benefits for a particular therapy do not overwhelmingly support its use.”

Pharmacotherapy* is directed toward modifying the symptoms of IBS that ranges from IBS-C which is constipation-dominant, to IBS-D – diarrhea dominant, and IBS-M which has both. Among the suggested or recommended pharmacological interventions are antispasmodics, antidepressants, and eluxadoline (IBS-D), lubiprostone (IBS-C), and linaclotide (IBS-C).

  • Antidepressants: A 2011 Cochrane review concluded that SSRIs and tri-cyclic antidepressants have “good” evidence of effectiveness, but effectiveness may be depend on “the individual patient.”[iii]
  • Antispasmodics: Found by this same review to be effective in some patients.  About 3-7 patients need to be treated in order to produce 1 successful outcome (NNT).
  • Bulking agents: Cochrane found no evidence to support bulking agents (soluble and insoluble fiber.)
  • Psychological therapies: A recent review (2019) suggests that while the evidenced is of limited quality, psychological therapies (cognitive behavioral therapy (CBT), relaxation therapy, multi-component psychological therapy, hypnotherapy, and dynamic psychotherapy) appear to be helpful.

The website www.drugs.com lists 79 medications (Rx, OTC, off-label) used to treat IBS. Over the counter medications are used frequently. OTC bismuth and loperamide (Kayopectate, Pepto-Bismol, Imodum)have been shown to provide relief of diarrhea but have no effect on other IBS symptoms. IBS-C can be treated with a variety of drugs intended to get things moving when constipation strikes. Dietary fiber sources, osmotic laxitives, stool softeners, and stimulant laxatives have evidence of varying degrees of effectiveness and individual risk profiles for adverse events.

Our final installment covering IBS in April will look at the evidence for integrative healthcare treatment options for patients dealing with Irritable Bowel Syndrome.


[i]Canadian Assoc. of Gastroenterology. (Accessed 4/2/19 at https://www.cag-acg.org/images/publications/CAG_CPG_for_Management_of_IBS_JCAG_Jan2019.pdf)

[ii] Weinberg, David S. et al. American Gastroenterological Association Institute Guideline on the Pharmacological Management of Irritable Bowel Syndrome. Gastroenterology , Volume 147 , Issue 5 , 1146 – 1148

[iii] Ruepert  L, Quartero  AO, de Wit  NJ, van der Heijden  GJ, Rubin  G, Muris  JWM. Bulking agents, antispasmodics and antidepressants for the treatment of irritable bowel syndrome. Cochrane Database of Systematic Reviews 2011, Issue 8. Art. No.: CD003460. DOI: 10.1002/14651858.CD003460.pub3.