Effect of Memantine Oral Pump on Language in Patients With Probable Alzheimer's Disease

Inclusion Criteria: * probable Alzheimer's disease in accordance with NINCDS-ADRDA criteria * MMSE score equal to or less than 20 * Brain CT or MRI scan performed within the past 12 months * living or having regular visit at least three times a week from caregiver * able to visit outpatient clinic and to perform cognitive function test * already taking stable dose of donepezil for 3 months prior to screening * subject and caregiver who signed informed consent Exclusion Criteria: * involved in another clinical trial within 4 weeks prior to screening * severe or unstable disease: acute or severe asthma, unstable or severe cardiovascular disease, acute peptic ulcer,chronic renal failure * bradycardia (pulse rate less than 50bpm), sick sinus syndrome * any laboratory finding including cognitive impairments(vitamine B12 or folic acid, syphilis, thyroid disease) * severe auditory or visual disturbance * other degenerative disease or psychosis * taken any drug used for the treatment of Alzheimer's disease or dementia