A 68-year-old man with idiopathic Parkinson disease on levodopa develops well-formed visual hallucinations and paranoid delusions. Which antipsychotic is the MOST appropriate choice?
- A Haloperidol
- B Risperidone
- C Quetiapine ✓
- D Trifluoperazine
Correct answer: C. Quetiapine
Explanation
Quetiapine is preferred because it blocks D2 receptors minimally at therapeutic doses and does not worsen parkinsonian motor symptoms, unlike risperidone which reliably aggravates parkinsonism even at low doses. Typical agents such as haloperidol and trifluoperazine are strongly D2 blocking and contraindicated. Clozapine is equally safe for motor symptoms but is reserved for refractory cases because of agranulocytosis monitoring requirements.
Reference: Kaplan and Sadock's Synopsis of Psychiatry, 11th ed.
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