Dihydro Donepezil, also known as Dihydro E2020, is a metabolite derived from Donepezil. Donepezil is a highly specific and potent inhibitor of acetylcholinesterase (AChE) with IC50 values of 8.12 nM and 11.6 nM for butyrylcholinesterase (bAChE) and human acetylcholinesterase (hAChE), respectively [1].