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Clozapine Side Effects — MRCPsych Paper B MCQ

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HardSchizophrenia & PsychosisClozapine Side EffectsMRCPsych Paper B

A 31-year-old man taking clozapine 450 mg daily and amitriptyline 50 mg at night has not opened his bowels for 5 days. He has progressive abdominal distension, nausea and reduced bowel sounds. Abdominal X-ray shows marked faecal loading with colonic dilatation. Which progression is the most clinically important reason for immediate escalation rather than routine outpatient management of constipation?

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Correct answer: C — Paralytic ileus with intestinal ischaemia and bowel perforation

Explanation lettering: D = shown as B · B = shown as D

Clozapine-induced gastrointestinal hypomotility can progress from constipation and faecal loading to pseudo-obstruction or paralytic ileus, intestinal ischaemia, necrosis and perforation. Abdominal distension, nausea, reduced bowel sounds and colonic dilatation indicate more than uncomplicated constipation and require urgent medical assessment. Amitriptyline adds anticholinergic burden and increases the risk. Faecal impaction (B) is itself serious and may require manual evacuation, but ileus with ischaemia or perforation is the most immediately life-threatening progression. Haemorrhoids and rectal prolapse may follow chronic straining but do not explain the hypomotility syndrome. Irritable bowel syndrome is a functional disorder and does not result from acute faecal loading or cause ileus and perforation.

Reference: Viatris Products Limited. Clozapine Viatris 100 mg Tablets: Summary of Product Characteristics, sections 4.4 and 4.8. Text revised February 2026; eMC updated 13 March 2026. https://www.medicines.org.uk/emc/product/15498/smpc