A 70-year-old man with idiopathic Parkinson's disease on levodopa develops vivid visual hallucinations requiring an antipsychotic. His orthostatic blood pressure drop is mild and cognition shows mild impairment. Which antipsychotic is the preferred choice?
- A Haloperidol
- B Quetiapine ✓
- C Risperidone
- D Amisulpride
Correct answer: B. Quetiapine
Explanation
Quetiapine is the usual first-choice antipsychotic in Parkinson's disease because it has negligible D2 receptor blockade at clinical doses and does not worsen motor symptoms. Clozapine is equally motor-safe but requires mandatory weekly hematologic monitoring for agranulocytosis, limiting its use to refractory cases. Haloperidol and risperidone are potent D2 blockers and reliably exacerbate parkinsonism, while amisulpride is also a strong D2 antagonist.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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