TCAs in Elderly — MRCPsych Paper B MCQ

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EasyOld Age PsychiatryTCAs in ElderlyMRCPsych Paper B

An 80-year-old man with major depressive disorder has symptomatic benign prostatic hyperplasia, including hesitancy, a weak urinary stream and a sensation of incomplete bladder emptying. His GP prescribes amitriptyline. Which adverse effect is of greatest concern specifically because of his prostatic enlargement?

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Correct answer: C — Acute urinary retention

Amitriptyline has substantial antimuscarinic activity. Reduced muscarinic stimulation of the detrusor impairs bladder contraction and can precipitate acute urinary retention in a man who already has bladder-outflow obstruction from benign prostatic hyperplasia. The UK SmPC therefore advises caution in patients with prostatic hypertrophy or urinary retention. Somnolence and postural hypotension are also important adverse effects of amitriptyline in older adults, but they are not specifically related to prostatic enlargement. Weight gain is a recognised longer-term effect but is not the principal urological hazard. Serotonin syndrome is primarily a concern when amitriptyline is combined with other serotonergic medicines; no such combination is described here.

Reference: Electronic Medicines Compendium. Amitriptyline 50 mg Film-Coated Tablets, Summary of Product Characteristics, sections 4.4 and 4.8. Updated 9 April 2025. https://www.medicines.org.uk/emc/product/10851/smpc