Memantine for Treatment of Cognitive Impairment in Patients With Parkinson's Disease and Dementia

Inclusion Criteria: Diagnosis of idiopathic PD, as defined by UK Brain Bank Criteria. Age onset of PD > 35 years old Adult men and women, current age > 50 years English speaking Any race or ethnic background. Hoehn and Yahr Stage I-V, provided able to participate verbally in clinical assessments and travel to clinic. Diagnosis of dementia secondary to PD, as defined by DSM-IV-TR. Stable medical health Taking stable doses for 2 months of non-excluded medications. Outpatient status (may be residing in a long-term care facility). Able to attend all study visits with an informed caregiver/partner who is willing to provide information on the patient's clinical status and response to treatment. Presence of an informed caregiver willing to take part in weekly phone call follow-up calls for the duration of study enrollment. Provision of informed consent by patient and caregiver and/or legal guardian. On stable antiparkinsonian therapy for 2 months. If history of major depression or anxiety disorder, must have stable symptoms and be on stable therapy for 2 months. If taking antipsychotic medication, must be on stable therapy for 2 months. If taking nonsteroidal anti-inflammatory medication, selegiline, or estrogen, must be on a stable dose for 30 days before study entry. If taking cholinesterase inhibitors, must be on for at least 6 months and a stable dose for 2 months before randomization. Exclusion Criteria: History or evidence of neurodegenerative disorder other than PD. Meets clinical criteria for Dementia with Lewy Bodies. History or current evidence of epilepsy. Participation in another investigational drug trial within 2 months of screening. Treatment with memantine within 60 days of screening. Current symptomatic Major Depressive Disorder, as based on Hamilton Depression Rating Scale Score > 17. Current clinically significant hepatic, kidney disease, gastrointestinal, endocrine, or cardiovascular disease, including evidence of second or third degree heart block. [Note, patients with controlled hypertension (supine diastolic BP<95 mm Hg), complete or partial right bundle branch block, pacemakers, or deep brain stimulators may be included.].