A 50-year-old man with advanced Parkinson's disease on levodopa/carbidopa 250/25 mg four times daily develops involuntary writhing movements of the face, trunk, and limbs appearing 60-90 minutes after each dose. These are absent at trough. What is this phenomenon and how should it be managed?
- A Diphasic dyskinesia — reduce levodopa dose and add amantadine
- B Peak-dose dyskinesia — reduce individual levodopa dose (while maintaining total daily dose) and add amantadine ✓
- C Off-period dystonia — increase levodopa dose frequency
- D Wearing-off phenomenon — switch to sustained-release levodopa
Explanation
Peak-dose dyskinesias appear at the time of maximum plasma levodopa concentration (60-90 min post-dose) when striatal dopamine is highest. Management involves fractionating the total daily levodopa dose into smaller, more frequent doses (to reduce peak plasma concentration) without reducing the total daily dose, combined with amantadine — the only drug with proven anti-dyskinetic efficacy via NMDA antagonism. Diphasic dyskinesia occurs at both onset and offset of the dose. Off-period dystonia is painful cramping at trough. Wearing-off is predictable early-off before the next dose.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.