CNS Pharmacology USMLE Step 1 Practice Question
A 67-year-old man with Parkinson disease treated with levodopa/carbidopa 25/100 mg four times daily for 5 years presents with involuntary writhing movements of his extremities and trunk that worsen 2–3 hours after each dose and improve with the next medication administration. Vital signs: BP 138/82, HR 88, RR 16, Temp 37°C, SpO2 98%. Neurological examination reveals choreoathetoid movements predominantly affecting the neck and upper limbs during peak plasma drug levels. MRI brain shows no acute abnormalities. He denies recent medication changes. Which of the following best describes this complication?
Answer choices
- AChorea from excessive dopamine in the cerebellum
- BAkathisia from serotonin depletion
- CDystonia from carbidopa accumulation in the basal ganglia
- DTremor from inadequate MAO-B inhibition
- EDyskinesias from long-term levodopa exposure and dopamine receptor sensitizationCorrect answer
- FTardive dyskinesia from dopamine D2 receptor blockade
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