Determine the effect of dimebon (latrepirdine) on cognition and memory

Determine the effect of dimebon on self-care and daily function

Determine the effect of dimebon (latrepirdine) on global function

Determine the effect of dimebon on behavior

Determine the effect of dimebon on quality of life

Determine the safety and tolerability of treatment with dimebon

Randomized, placebo-controlled, double-blind safety and efficacy trial of oral dimebon (latrepirdine) in patients with mild to moderate Alzheimer's disease who are stable on donepezil

1050 patients randomized into 3 equal groups

—Dimebon 5 mg TID

—Dimebon 10 mg TID for 7 days, then 20 mg TID for remainder

—Placebo

66% of patients will receive dimebon

Patients are required to participate in the study with a caregiver who can assist at least 5 days a week for 3 hours a day

Efficacy assessments to be performed at baseline and weeks 13, 26, 39, and 52

Patients will receive 52 weeks of treatment; those who complete the 52-week study (placebo and treatment groups) may then choose to participate in an open-label extension study (all patients receive dimebon [latrepirdine])

Male or female ≥ 50 years of age

Diagnosis of probable Alzheimer's disease according to the following criteria:

Stable on donepezil for at least 6 months

At least 8 years of education, with pre-Alzheimer's capability of reading, writing, and communicating effectively

Ability to give informed consent, or to have a legally authorized representative provide consent

A guardian or caregiver who: provides assistance at least 5 days per week for at least 3 hours per day; can accompany the participant to all study visits; and can supervise administration of the study drug (guardian must be able to read, write, and be capable of providing responses to the ADCS-ADL, CIBIC-plus, NPI, and RUD-Lite and EQ-5D assessment tools)

Participants may be living in an assisted-care facility, if living independently (not requiring 24-hour care and supervision)

Any major medical illness or unstable medical condition within 6 months of screening that may interfere with the patient's ability to comply with study procedures and abide by study restrictions

Residence in a nursing home or assisted-living facility with a need for 24-hour care and supervision

A history of hypersensitivity to dimebon (latrepirdine) or other antihistamines

Certain laboratory abnormalities apparent at screening visit

Use of non-donepezil cholinesterase inhibitors 6 months prior to enrollment

Use of memantine within 90 days of enrollment

Use of prescription medical food or prescription nutraceuticals marketed for AD or cognitive impairment within 30 days of screening and throughout the study

Participation in an Alzheimer's disease investigational drug study within 90 days of enrollment