To estimate the absorption, safety, and tolerability of a dimebon transdermal solution relative to the dimebon immediate release oral formulation.

Inclusion Criteria:

• Caucasian, male or females, 50 to 85 years inclusive.
• Subjects must have adequate space available on each side of the upper or middle back that is free from excessive hair, broken or irritated skin, tattoos, scars, moles, acne, and sunburn.

Exclusion Criteria:

• Evidence or history of any major medical or psychiatric illness or unstable medical condition within six months of Screening that may increase the risk associated with study participation.
• Subjects with any central nervous system disease including Alzheimer's disease, Parkinson's disease, Huntington disease, or any form of dementia.
• Subjects with any history of stroke, known cerebrovascular disease or subjects with any history of structural brain disease.
• Any history of epilepsy, seizure disorder (i.e., including febrile seizures) or convulsion.
• Subjects with any skin disorders that might prevent application of the dimebon solution including, but not limited to, any known sensitivity to adhesives.