A 60-year-old man with Parkinson disease on levodopa/carbidopa develops involuntary writhing movements of the trunk and limbs that occur 1–2 hours after each dose. These movements are absent just before the next dose. This is classified as:

• A Wearing-off fluctuations
• B Off-period dystonia
• C Drug-induced parkinsonism
• D Peak-dose dyskinesias ✓

Explanation

Peak-dose dyskinesias (choreiform/athetoid movements) occur at the time of maximum levodopa plasma concentration (1–2 hours post-dose) and represent hypersensitivity of striatal dopamine receptors from chronic pulsatile stimulation. Wearing-off (end-of-dose deterioration) is when PD symptoms return before the next dose. Off-period dystonia typically causes painful foot/leg cramps in the early morning before the first dose. Management of peak-dose dyskinesias includes dose reduction, using controlled-release formulations, or adding amantadine (which has anti-dyskinetic properties).

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.