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Dyskinesia refers to an impairment of voluntary movement. The resultant tics and other movements are often referred to as dyskinesias. Dyskinesia is sometimes caused by long-term use of anti-psychotic drugs or other dopamine antagonists like the antiemetic metoclopramide. The effect of these drugs can be tardive, meaning the dyskinesia continues or appears even after the drugs are no longer taken (see Tardive dyskinesia). In context of Parkinson's disease, dyskinesias are often the result of chronic levodopa (L-dopa) therapy. These motor fluctuations occur in more than half of PD patients after 5 to 10 years of levodopa therapy, with the percentage of affected patients increasing over time.Obeso JA, et al. The evolution and origin of motor complications in Parkinson's disease. ''Neurology''. 2000;55(suppl 4):S13-S20. Dyskinesias most commonly occur at the time of peak L-dopa plasma concentrations and are thus referred to as peak-dose dyskinesias. As patients advance, they may evidence diphasic dyskinesias, which occur when the drug concentration rises or falls. The use of MDMA (ecstasy) has been shown to enhance the effects of L-Dopa while reducing the associated dyskinesia in patients with Parkinson's disease .
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