This study will evaluate the motor and cognitive benefits of low-dose zolpidem in Parkinson's.

Zolpidem is a hypnotic drug which at sub-sedative doses has been shown to improve both motor and cognitive deficits in stroke, dementia and Parkinson's. This has led to the hypothesis that low-dose zolpidem will be effective in early-stage Parkinson's, delaying the need for dopamine-replacement interventions, as an adjunct therapy, and in late-stage Parkinson's where current interventions are ineffective for motor and cognitive decline. At present, the symptoms of late-stage Parkinson's are the most debilitating and the least well-controlled. Here, the investigators propose a placebo controlled double-blinded proof-of-concept study in order to determine the benefits of taking low-dose zolpidem in late-stage Parkinson's. The study will take place over 12 months. 28 participants, diagnosed with Parkinson's for at least 5 years will be recruited; 14 participants will take zolpidem (5 mg) and 14 placebo, each morning for 4 days. In the clinic (day 1) clinical assessments will include the motor III of the Unified Parkinson's Disease Rating Scale (UPDRS) and cognitive verbal fluency tasks which will be conducted at baseline and 1 hour following drug administration. Each participant will then be issued with a smartphone with application to objectively test their motor performance 4 times a day, over the next six days (3 days on drug, 3 days off drug). This study will provide the necessary data on drug efficacy in order to design a phase II clinical trial for the use of low-dose zolpidem in late-stage Parkinson's.

Inclusion Criteria:

Diagnosis of idiopathic Parkinson's and Hoehn and Yahr score of 2.5 or more; Willing to participate and refrain from driving whist taking zolpidem/placebo; Within age range 40 to 80 years.

Exclusion Criteria:

Any contraindications as stated in Summary of Product Characteristics (SmPC) for zolpidem:- Hypersensitivity to zolpidem tartrate; Obstructive sleep apnoea; Myasthenia gravis; Severe hepatic insufficiency; Acute and/or severe respiratory depression; Psychotic illness.

and in addition: - Unable or unwilling to give informed consent ; Current therapy with central nervous system (CNS) depressants; Current therapy with Cytochrome P450 (CPY450) inhibitors or inducers (specifically CYP3A4); Pregnancy and breast feeding women; History of alcohol or substance abuse; Employed in a role that involves driving or operating heavy machinery; Participation in another interventional clinical trial.