A 55-year-old man with Parkinson's disease on levodopa-carbidopa for 6 years develops involuntary writhing movements of his limbs and trunk approximately 1 hour after each dose. These movements are most problematic at peak medication levels. What is this phenomenon called and what is the most appropriate management?
- A Peak-dose dyskinesias; reduce individual levodopa dose and increase frequency, or add amantadine ✓
- B Wearing-off phenomenon; add COMT inhibitor
- C Early morning akinesia; add pramipexole
- D Diphasic dyskinesias; switch to immediate-release levodopa
Correct answer: A. Peak-dose dyskinesias; reduce individual levodopa dose and increase frequency, or add amantadine
Explanation
Peak-dose dyskinesias occur when levodopa plasma levels are at their highest and represent a motor complication of long-term levodopa therapy due to postsynaptic dopaminergic receptor sensitisation. Management involves reducing individual doses while increasing frequency (fractionating doses), using controlled-release preparations, or adding amantadine — which has NMDA antagonist properties that reduce dyskinesia severity. Wearing-off (end-of-dose deterioration) is different and treated by COMT inhibitors, MAO-B inhibitors, or long-acting dopamine agonists.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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