A Multicenter, Randomized, Double-blind, Placebo-controlled Clinical Trial to Assess the Efficacy of Acetyl-L-carnitine in Patient With Alzheimer's Disease

Inclusion Criteria: * More than 50 Years * probable Alzheimer disease according to DSM-IV and NINCDS-ADRDA standard * 12≤K-MMSE(screening)≤26 * be able to perform examinations * Patient taking donepezil(5mg or 10mg/day) more than 3 months * be able to visit to hospital with caregiver Exclusion Criteria: * possible or probable or definite vascular dementia according to NINDS-AIREN standard * CNS disease(Cerebrovascular diseases, Epilepsy etc) to cause dementia * Illiteracy * Patient taking galantamine, memantine, rivastigmine within three months * Patient taking brain enhancer, thyroid hormone within 4 weeks * Patient taking Central nervous system stimulant, Antipsychotic agent, anticholinergic agent within 2 weeks * at screenig blood test: AST, ALT≥ 3 X upper limit of normal range or Hb≤8g/dL or platelet\<100,000/mm3 or Serum creatinine ≥ 3 X upper limit of normal range * Abnormal result of Vit.B12, Syphilis serology, TSH * Severe Depression, Schizophrenia, Alcoholism, Drug addiction * Parkinson's disease (need to drug therapy) * Angina, Myocardial infarction, ischemia within six months * Head injury with sense of loss within six months * Patient taking other IP within three months * Hypersensitivity to IP * Sever Hearing problems or Visual impairment