The purpose of this study is to find out if a medication that increases levels of a brain chemical called acetylcholine will improve balance and reduce falls in patients with parkinson's disease who have the problem of very poor balance and are frequently falling or nearly falling on a daily basis. Donepezil, a drug approved for the treatment of Alzheimer's dementia, will reduce falls in subjects with Parkinson's disease and balance impairment.

This trial is a double-blinded cross-over design comparing donepezil with placebo in 40 subjects with idiopathic Parkinson's disease who report frequent falls or near falls (>2/week). The purpose of this study is to find out if a medication that increases levels of a brain chemical called acetylcholine will improve balance and reduce falls in patients with parkinson's disease who have the problem of very poor balance and are frequently falling or nearly falling on a daily basis. Donepezil, a drug approved for the treatment of Alzheimer's dementia, will reduce falls in subjects with Parkinson's disease and balance impairment.

Inclusion Criteria:

• Age over 21
• Diagnosis of Parkinson's disease
• Treated with dopaminergic medication for at least 1 year

Exclusion Criteria:

• Must be ambulatory (can use walker or cane)
• No obvious remediable cause of falls
• Falls are on basis of non-CNS etiologies (cardiogenic, orthopedic, peripheral neuropathy, etc)
• Dementia present (MMSE < 25)
• Not taking cholinergic or anticholinergic medications 10 days prior to screening visit
• No Warfarin use

23 participants were enrolled into the study. 3 participants screen failed.

Small number of subjects and lack of objective measurement to quantify falls. The most difficult condition to exclude was co-existing freezing of gait.