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Clozapine-associated faecal impaction with colonic dilatation — MRCEM SBA MCQ

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HardMental health and behavioural emergenciesClozapine-associated faecal impaction with colonic dilatationMRCEM SBA

A 47-year-old man with treatment-resistant schizophrenia attends the emergency department with worsening abdominal pain and vomiting. He takes clozapine; oxybutynin was added two weeks ago for urinary urgency. He has passed no formed stool for five days, although he passed a small amount of watery stool this morning. His abdomen is markedly distended and tender without guarding. His pulse is 118/min and blood pressure 96/60 mmHg. CT shows a rectosigmoid faecaloma with proximal colonic dilatation and no perforation. Which immediate management and disposition plan is most appropriate?

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Correct answer: D — Withhold both drugs; give intravenous fluids and refer urgently to surgery.

The watery stool does not exclude constipation: it may represent overflow around the faecaloma. Distension, vomiting and CT-confirmed proximal dilatation establish a serious bowel complication rather than uncomplicated clozapine-associated constipation. Oxybutynin adds an anticholinergic risk. Withhold both drugs, address his circulatory compromise with intravenous fluids, and obtain urgent surgical assessment. Clozapine-associated faecal impaction or obstruction warrants immediate specialist treatment; the mental health team should also be informed about the interruption to clozapine. ([sps.nhs.uk](https://sps.nhs.uk/articles/managing-constipation-in-people-taking-clozapine/)) A resembles treatment for uncomplicated constipation, but neither a psychiatric ward nor routine oral laxatives address the established complication. B correctly withholds the drugs, yet substitutes oral laxatives and medical observation for urgent assessment of the dilated bowel. Oral laxative treatment is advised after intestinal obstruction has been excluded, which it has not been here. C recognises the need for fluids and surgical review but continues clozapine despite faecal impaction. E addresses the drugs and circulation but sends a patient with an acute bowel emergency to an unsuitable admitting service. ([sps.nhs.uk](https://sps.nhs.uk/articles/managing-constipation-in-people-taking-clozapine/))

Reference: Clozapine: reminder of potentially fatal risk of intestinal obstruction, faecal impaction, and paralytic ileus (26 October 2017) — https://www.gov.uk/drug-safety-update/clozapine-reminder-of-potentially-fatal-risk-of-intestinal-obstruction-faecal-impaction-and-paralytic-ileus Managing constipation in people taking clozapine (14 October 2022) — https://sps.nhs.uk/articles/managing-constipation-in-people-taking-clozapine/ Clozapine clinic protocols (Approved 5 March 2024; webpage last updated 16 June 2025) — https://www.rdash.nhs.uk/policies/clozapine-clinic-protocols/