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

1. Diagnosis of idiopathic PD, as defined by UK Brain Bank Criteria.

2. Age onset of PD > 35 years old

3. Adult men and women, current age > 50 years

4. English speaking

5. Any race or ethnic background.

6. Hoehn and Yahr Stage I-V, provided able to participate verbally in clinical assessments and travel to clinic.

7. Diagnosis of dementia secondary to PD, as defined by DSM-IV-TR.

8. Stable medical health

9. Taking stable doses for 2 months of non-excluded medications.

10. Outpatient status (may be residing in a long-term care facility).

11. 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.

12. Presence of an informed caregiver willing to take part in weekly phone call follow-up calls for the duration of study enrollment.

13. Provision of informed consent by patient and caregiver and/or legal guardian.

14. On stable antiparkinsonian therapy for 2 months.

15. If history of major depression or anxiety disorder, must have stable symptoms and be on stable therapy for 2 months.

16. If taking antipsychotic medication, must be on stable therapy for 2 months.

17. If taking nonsteroidal anti-inflammatory medication, selegiline, or estrogen, must be on a stable dose for 30 days before study entry.

18. If taking cholinesterase inhibitors, must be on for at least 6 months and a stable dose for 2 months before randomization

1. History or evidence of neurodegenerative disorder other than PD.

2. Meets clinical criteria for Dementia with Lewy Bodies.

3. History or current evidence of epilepsy.

4. Participation in another investigational drug trial within 2 months of screening.

5. Treatment with memantine within 60 days of screening.

6. Current symptomatic Major Depressive Disorder, as based on Hamilton Depression Rating Scale Score > 17.

7. 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.].