Antipsychotic in PDD — MRCPsych Paper B MCQ

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ModerateOld Age PsychiatryAntipsychotic in PDDMRCPsych Paper B

A 74-year-old man with Parkinson's disease dementia has persistent, distressing visual hallucinations. Delirium and other reversible causes have been excluded, his antiparkinsonian medication has been reviewed by a specialist, and standard treatment has been ineffective. Which antipsychotic is most appropriate and has the lowest propensity to worsen his parkinsonism?

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Correct answer: A — Clozapine

Clozapine is the best answer. It has weak dopamine D2 receptor blockade and a low propensity to cause extrapyramidal adverse effects, so it is relatively unlikely to worsen parkinsonism. NICE recommends offering clozapine for hallucinations or delusions in Parkinson's disease when standard treatment has failed; lower doses are required, and mandatory haematological monitoring is essential. Haloperidol has potent D2 antagonism and can markedly exacerbate parkinsonism. Risperidone and aripiprazole can also worsen motor symptoms through clinically significant D2 receptor effects. Olanzapine should not be offered: UK guidance and its SmPC specifically report worsening of parkinsonian symptoms without established benefit. All antipsychotics require particular caution in Parkinson's disease dementia because severe sensitivity reactions can occur.

Reference: NICE. Parkinson’s disease in adults (NG71), recommendations 1.5.17–1.5.20. Published 2017; current page updated May 2026. https://www.nice.org.uk/guidance/ng71/chapter/Recommendations