Long-term use of amphetamines may increase the risk of Parkinsons disease (PD):  in one retrospective study with over 40,000 participants it was concluded that amphetamine abusers generally had a 200% higher chance of developing PD versus those with no history of abuse; the risk was much higher in women, almost 400%. There remains some controversy as of 2017.Levodopa-induced dyskinesia (LID) is evident in patients with Parkinsons disease who have been on levodopa (L‑DOPA) for prolonged periods of time. LID commonly first appears in the foot, on the most affected side of the body. There are three main types that can be classified on the basis of their course and clinical presentation following an oral dose of L‑DOPA:
Off-period dystonia – correlated to the akinesia that occurs before the full effect of L‑DOPA sets in, when the plasma levels of L‑DOPA are low. In general, it occurs as painful spasms in the foot. Patients respond to L‑DOPA therapy. Diphasic dyskinesia – occurs when plasma L-DOPA levels are rising or falling. This form occurs primarily in the lower limbs (though they can happen elsewhere) and is usually dystonic (characterized by apparent rigidity within muscles or groups thereof) or ballistic (characterized by involuntary movement of muscles) and will not respond to L‑DOPA dosage reductions. Peak-dose dyskinesia – the most common form of levodopa-induced dyskinesia; it correlates with the plateau L‑DOPA plasma level. This type usually involves the upper limbs more (but could also affect the head, trunk and respiratory muscles), is choreic (of chorea), and less disabling.
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