Placebo-Controlled Crossover Study to Evaluate Donepezil and MK-3134 for Reversal of Cognitive Impairment Associated With Scopolamine Administration (3134-005)(COMPLETED)

The drug, scopolamine, can result in short-term impairments of cognitive function, attention, and memory that resemble those seen in aging and Alzheimer\'s disease. This study tested the capability of both individual and combined doses of MK-3134 and the current standard treatment: donepezil (Aricept), to reverse such impairments, following a single dose of scopolamine. Participants were evaluated after each of 5 different treatment periods (in a cross-over, double-dummy design): A: placebo to match both donepezil (oral \[PO\]) and MK-3134 (PO) followed by placebo scopolamine (subcutaneous \[SQ\]); B: placebo to match both donepezil (PO) and MK-3134 (PO), followed by scopolamine SQ; C: MK-3134 (PO) followed by scopolamine SQ; D: donepezil (PO) followed by scopolamine SQ; E: MK-3134 (PO) and donepezil (PO) followed by scopolamine SQ. The doses of MK3134, donepezil, and scopolamine were the same over all treatment arms in which the specified drug was administered. There were 8 total visits for each treatment period, including 5 Treatment Visits requiring 14-day intervals between visits for study-drug washout. Participants were assessed for cognitive function before and after each treatment period during the Treatment Visits.