Trial of Xyrem for Excessive Daytime Sleepiness and Sleep Disturbance in Parkinson's Disease (PD)

Inclusion Criteria: * Male or female with a diagnosis of idiopathic PD. * Age between 30 and 75, inclusive. -Hoehn \& Yahr Stage 1.5 - 4.0 in the practically defined medication "OFF". - * History \> 2 months of excessive daytime sleepiness confirmed at baseline/screening by an Epworth Sleepiness Scale score of \> 10. * History \> 2 months of nocturnal sleep disturbances consisting of insomnia, fragmented sleep and/or non-restorative sleep. * Folstein Mini-Mental State Exam score of \> 24. * Birth control for sexually active women of childbearing potential (e.g. abstinence, hormonal contraception, barrier method, intrauterine device). * Evidence of a personally signed and dated informed consent form document indicating that the subject (or a legally acceptable representative) has been informed of all pertinent aspects of the trial. * Subjects who are willing and able to comply with scheduled visits, treatment plan, and other study procedures. * Stable dose of medications, defined as no change in dose or regimen of medications for at least 3 months prior to Screen Visit. Exclusion Criteria: * Known idiopathic sleep pathology: sleep apnea and narcolepsy. * Serious co-morbid disease --Atypical parkinsonism (e.g., Parkinson "plus" syndrome, secondary Parkinson's syndrome). --Significant neurological symptoms not accounted for by PD. --Significant psychiatric symptoms or dementia. * Sexually active women of childbearing potential without adequate form of birth control. * Pregnancy or lactation. * Mini-mental status examination of \< 25. * Participation in another clinical trial of another investigational agent or device within the previous 60 days. * Current abuse of alcohol or drugs. * Active or prior malignancy other than cutaneous basal cell carcinoma or in situ carcinoma of the uterine cervix. * Known hypersensitivity to sodium oxybate or other constituents of the product. * Any medical conditions that are contraindications to the use of sodium oxybate or significant hepatic impairment. * Patients being treated with sedative hypnotic agents or other central nervous system (CNS) depressants. * Subjects taking warfarin. * Patients with succinic semialdehyde dehydrogenase deficiency. * Subjects who, in the opinion of the investigator, are not able to comply with the requirements of the study. * Any other condition that, in the investigator's opinion, would cause a significant hazard to the subject.