A study by Seripa found that variants of CYP2D6 associated with decreased or absent enzymatic activity (namely, CYP2D6*41, CYP2D6*9, CYP2D6*29, CYP2D6*3, CYP2D6*4, CYP2D6*7, CYP2D6*8, CYP2D6*14, CYP2D6*6, CYP2D6*17, CYP2D6*12, and CYP2D6*10, as well as gene deletion—CYP2D6*5) were associated with response to donepezil at 6 months in Italian AD patients (Seripa et al., 2011). Here, CYP2D6 is linked to Alzheimer disease.