We evaluated the effect of memantine administration from baseline on Clinical Global Impression-Improvement scale , mini mental state examination ( MMSE ) , Clock Drawing Test ( CDT ) , Neuropsychiatric Inventory ( NPI ) , Japanese version of the Zarit Burden Interview ( J-ZBI ) and NIRS in two groups , donepezil administration memantine combination group ( combination group , n = 19 ) donepezil administration memantine non-administration group ( control group , n = 18 ) were assessed at weeks 0 , 4 , 12 , and 24 .