As PD progresses, it becomes increasingly difficult to adequately control symptoms with medications. The most common problems that arise are motor complications, which include motor fluctuations and dyskinesias.
Motor fluctuations refer to unanticipated loss of effect of a given dose of levodopa-instead of a smooth, predictable symptomatic benefit, the patient may lose benefit earlier than usual (termed "wearing off") or may suddenly switch from "on" (symptoms controlled) to "off" (symptoms return).
Dyskinesias are involuntary movements that occur when dopamine levels are too high. Motor complications are discussed in more detail in the section "Complications of Treatment."