A transdermal delivery system for systemic delivery of donepezil is described, where the system comprises an adhesive matrix drug reservoir layer comprised of a copolymer of acrylic acid/vinyl acetate, triethyl citrate, and donepezil base generated in situ by reaction of donepezil HCl and an alkaline salt. The system is provided for treatment of Alzheimer's disease, and achieves transdermal delivery of the therapeutic agent at steady state that is bioequivalent to administration of the therapeutic agent orally.