Parkinson's Disease - Levadopa (L-dopa)

Psychiatric and Mental Side Effects. The major adverse effects of the drug are psychiatric. Patients taking levodopa, especially in combination with other drugs, can experience the following:

Confusion.
Extreme emotional states, particularly anxiety.
Vivid dreams.
Visual and possibly auditory hallucinations. The drug may even unmask dementia that had not been previously noticed.
Effects on learning. L-dopa appears to have mixed effects on learning. It may actually improve working memory. However, some evidence suggests that it floods and impairs areas of the brain related to other learning functions (specifically as the ability to apply different rules of behavior in similar situations.)
Sleepiness and sleep attacks.

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Levodopa provokes fewer psychiatric side effects than other drugs used for Parkinson's disease, including anticholinergics, selegiline, amantadine, and dopamine agonists. Because psychiatric side effects often occur at night, if they are severe some physicians recommend reducing or stopping the evening dose.

The Wearing-Off Effect and Dyskinesia (Inability to Control Muscles)

Within four to six years of treatment with levodopa, the effects of the drug in many patients begin to last for shorter periods of time (called the wearing-off effect) and the following pattern may occur:

Patients may first notice slowness (bradykinesia) or tremor in the morning before the next dose is due.
Less commonly, some experience painful dystonia, muscle spasms that can cause sustained contortions of various parts of the body, particularly the neck, jaw, trunk, and eyes and possibly the feet.
Patients must increase the frequency of levodopa doses. This puts them at risk for dyskinesia (the inability to control muscles), which usually occurs when the drug level peaks. Dyskinesia can take many forms, most often uncontrolled flailing of the arms and legs or chorea, rapid and repetitive motions that can affect the limbs, face, tongue, mouth, and neck. Dyskinesia is not painful, but it is very distressing.
In some people, eventually L-dopa is effective only for one to two hours and most patients start to experience motor fluctuations. In about 15% to 20% of patients such fluctuations become extreme, a phenomenon known as the on-off effect, which consists of unpredictable, alternating periods of dyskinesia and immobility. Sometimes the symptoms switch back in forth within minutes or even seconds. (The transition may follow such symptoms as intense anxiety, sweating, and rapid heartbeats.)