Levodopa-induced dyskinesia

Levodopa-induced dyskinesia (LID) is a form of dyskinesia associated with levodopa (l-DOPA), used to treat Parkinson's disease. It often involves hyperkinetic movements, including chorea, dystonia, and athetosis.^[1]

In the context of Parkinson's disease (PD), dyskinesia is often the result of long-term dopamine therapy. These motor fluctuations occur in up to 80% of PD patients after 5–10 years of l-DOPA treatment,^[2] with the percentage of affected patients increasing over time.^[3] Based on the relationship with levodopa dosing, dyskinesia most commonly occurs at the time of peak l-DOPA plasma concentrations and is thus referred to as peak-dose dyskinesia (PDD). As patients advance, they may present with symptoms of diphasic dyskinesia (DD), which occurs when the drug concentration rises or falls. If dyskinesia becomes too severe or impairs the patient's quality of life, a reduction in l-Dopa might be necessary, however this may be accompanied by a worsening of motor performance. Therefore, once established, LID is difficult to treat.^[4] Amongst pharmacological treatments, N-methyl-D-aspartate (NMDA) antagonist, (a glutamate receptor), amantadine, has been proven to be clinically effective in a small number of placebo controlled randomized controlled trials, while many others have only shown promise in animal models.^[5][6] Attempts to moderate dyskinesia by the use of other treatments such as bromocriptine (Parlodel), a dopamine agonist, appears to be ineffective.^[7] In order to avoid dyskinesia, patients with the young-onset form of the disease or young-onset Parkinson's disease (YOPD) are often hesitant to commence l-DOPA therapy until absolutely necessary for fear of suffering severe dyskinesia later on.^{[citation needed]} Alternatives include the use of DA agonists (i.e. ropinirole or pramipexole) in lieu of early l-DOPA treatment which delays the use of l-DOPA. Additionally, a review ^[8] shows that highly soluble l-DOPA prodrugs may be effective in avoiding the in vivo blood concentration swings that potentially lead to motor fluctuations and dyskinesia.