Which medication is commonly used to treat dyskinesia related to Parkinson's disease therapy?

• A. Tolcapone
• B. Carbidopa-levodopa
• C. Amantadine
• D. Selegiline

Answer: (C)

Dyskinesias that develop with Parkinson’s disease treatment, especially from chronic levodopa use, come from abnormal, excessive dopaminergic signaling and altered glutamatergic activity in the basal ganglia. Amantadine is commonly used because it acts as an NMDA receptor antagonist, which dampens the glutamatergic overactivity contributing to these involuntary movements. By reducing this excitatory input in the motor circuits, amantadine helps lessen levodopa-induced dyskinesias and improves motor control during episodes when dyskinesias are prominent.

Tolcapone and other options play different roles: tolcapone inhibits COMT to extend levodopa’s effect but doesn’t specifically treat dyskinesia; carbidopa-levodopa is the main therapy for PD symptoms (and can even cause dyskinesias with long-term use rather than reliably treating them); selegiline is an MAO-B inhibitor that modestly helps symptoms and wearing-off but isn’t a primary treatment for dyskinesia.