Published: 1 December 2022


Microscopic colitis – could it be caused by a medicine?

Prescriber Update 43(4): 56–57
December 2022

Key messages

  • Microscopic colitis causes chronic, watery, non-bloody diarrhoea.
  • Consider medicines as a possible cause of microscopic colitis.

Microscopic colitis

Microscopic colitis is an inflammatory disease of the colon that causes chronic, watery, non-bloody diarrhoea.1 Patients often experience between 4 and 9 watery stools per day, but in rare cases, this number can exceed 15.1,2

Whilst the origin of microscopic colitis is largely unknown, it is likely to be multifactorial. Medicines, tobacco and autoimmune conditions have been identified as possible causes.2 There is evidence that a mucosal immune response occurs in genetically predisposed individuals and may contribute to the development of microscopic colitis.1 Diarrhoea associated with microscopic colitis is likely caused by mucosal inflammation.1 Microscopic colitis predominantly affects females and should be considered a possible cause of chronic diarrhoea, especially in middle-aged and older adults.1,2

There are two main subtypes of microscopic colitis, and each subtype is based on distinct histopathologic features:1–3
  • collagenous colitis – a layer of collagen develops in colon tissue
  • lymphocytic colitis – the number of lymphocytes (white blood cells) increases in colon tissue.
Collagenous colitis is diagnosed in cases where a broad subepithelial fibrous band is observed on histology.4 Lymphocytic colitis is diagnosed when an infiltration of more than 20 intraepithelial lymphocytes per 100 epithelial cells is observed.4 Diarrhoea, normal colonoscopy results and microscopic abnormalities in the colon are characteristics of both subtypes.4,5 Biopsies confirm a diagnosis.1

Medicines associated with microscopic colitis

The list below provides examples of medicines associated with microscopic colitis (list not exhaustive).
  • Non-steroidal anti-inflammatory drugs (NSAIDs): ibuprofen, diclofenac2, 6-8
  • Proton pump inhibitors: lansoprazole, omeprazole2, 6-8
  • Histamine-2 receptor antagonists: ranitidine, famotidine2,9
  • Selective serotonin reuptake inhibitors: sertraline, citalopram2, 6-8
  • Aspirin7
  • Clozapine7
  • Statins: simvastatin, atorvastatin1
  • Immune checkpoint inhibitors: pembrolizumab1,10
Concomitant use of proton pump inhibitors and NSAIDs may also increase the risk of microscopic colitis.1 Medicines associated with microscopic colitis are also associated with diarrhoea as a side effect.4 Healthcare professionals should consider such medicines as a possible cause of microscopic colitis.1


  1. Dietrich CF. 2022. Microscopic (lymphocytic and collagenous) colitis: clinical manifestations, diagnosis, and management. In: UpToDate 20 July 2022. URL: (accessed 22 September 2022).
  2. Shor J, Churrango G, Hosseini N, et al. 2019. Management of microscopic colitis: challenges and solutions. Clinical and Experimental Gastroenterology 12: 111-20. DOI: 10.2147/CEG.S165047 (accessed 14 July 2022).
  3. Mayo Clinic. 2021. Microscopic colitis 20 January 2021. URL: (accessed 12 July 2022).
  4. Lucendo AJ. 2017. Drug exposure and the risk of microscopic colitis: a critical update. Drugs in R & D 17(1): 79-89. DOI: 10.1007/s40268-016-0171-7 (accessed 20 September 2022).
  5. Zhang S-W, Xu R-H and Chen D. 2022. Drug exposure and risk of microscopic colitis: a systematic review and meta-analysis. Digestive Diseases (accepted, unedited manuscript). DOI: 10.1159/000526809 (accessed 20 September 2022).
  6. Nguyen GC, Smalley WE, Vege SS, et al. 2016. American Gastroenterological Association Institute Guideline on the Medical Management of Microscopic Colitis. Gastroenterology 150(1): 242-6. DOI: 10.1053/j.gastro.2015.11.008 (accessed 20 September 2022).
  7. American Gastroenterological Association. 2016. AGA Institute Guideline on the Management of Microscopic Colitis: Clinical Decision Support Tool. Gastroenterology 150(1): 276. DOI: 10.1053/j.gastro.2015.11.033 (accessed 22 September 2022).
  8. Hamdeh S, Micic D and Hanauer S. 2021. Drug-induced colitis. Clinical Gastroenterology Hepatology 19(9): 1759-79. DOI: 10.1016/j.cgh.2020.04.069 (accessed 29 September 2022).
  9. D'Sa FF, Fernandes EZ, Kesarkar SV, et al. 2022. Use of histamine-2 receptor antagonists and risk of inflammatory bowel diseases: a systematic review and meta-analysis of observational studies. Journal of Clinical Pharmacy and Therapeutics 47(8): 1103-11. DOI: 10.1111/jcpt.13662 (accessed 13 October 2022).
  10. Choi K, Abu-Sbeih H, Samdani R, et al. 2019. Can immune checkpoint inhibitors induce microscopic colitis or a brand new entity? Inflammatory Bowel Diseases 25(2): 385-93. DOI: 10.1093/ibd/izy240 (accessed 13 October 2022).
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