• Reduction of adverse event: [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Epworth Sleepiness Scale score for those with daytime sleepiness [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Neuropsychiatric Inventory Hallucinations question and Unified Parkinson's Disease Rating Scale Part I hallucinations question for those with hallucinations [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• circumference of lower leg/foot at greatest point of swelling for pedal edema [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Barratt Impulsiveness Scale for those with impulsive behavior [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  

• Maintenance of efficacy: [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Unified Parkinson's Disease Rating Scale Parts I-IV [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• PDQ-39 quality of life assessment [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Beck Depression Inventory and Beck Anxiety Inventory [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• patient and physician global impression of change [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Fatigue Severity Scale [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  
• Mini-Mental State Examination [ Time Frame: 3 months ] [ Designated as safety issue: No ]
  

Parkinson's disease (PD) is a progressive neurodegenerative disease. Symptomatic therapy is primarily aimed at restoring dopamine function in the brain.

Levodopa is the most effective symptomatic treatment; however, long term use is associated with motor fluctuations (periods of return of PD symptoms when medication effect wears off) and dyskinesia (drug induced involuntary movements including chorea and dystonia). Once patients develop motor fluctuations treatment options include increasing the frequency of levodopa dosing, switching to sustained-release levodopa, adding other therapies including MAO-B inhibitors, dopamine agonists, COMT inhibitors and in patients with severe motor fluctuations deep brain stimulation surgery. There are no good evidence based studies indicating whether the use of one of these class of drugs is superior to the other nor are there treatment algorithms that recommend which class of drug should be initiated when the patients initially develop motor fluctuations. It is believed that the efficacy of the different drug classes is similar. However, the frequency of adverse effects may differ between drug classes, but such studies are lacking. In clinical practice when patients develop adverse effects to a drug from one class, a drug from another class is substituted in an attempt to maintain efficacy with reduced adverse effects.

Dopamine agonists often have a higher risk of adverse effects compared to MAO B inhibitors. Therefore, the rationale for this study is that the addition of orally disintegrating selegiline after the reduction or discontinuation of the offending dopamine agonist will result in comparable efficacy with reduced adverse events. This study will assess the safety and efficacy of the addition of orally disintegrating selegiline in PD patients who are having adverse effects to dopamine agonists for which a dose reduction of the dopamine agonist is being considered. All patients in the study will receive orally disintegrating selegiline 1.25 mg once a day and the dose will be increased to 2.5 mg once a day if tolerated.

Comparisons: The status of the adverse event at the end of the study while on orally disintegrating selegiline will be compared to the adverse event at the start of the study. In addition, efficacy will be compared at the start of the study while on the dopamine agonist to the end of the study with orally disintegrating selegiline.