Over 70% of AD patients are deficient metabolizers for the CYP2D6/2C19/2C9 trigenic cluster; and for the CYP2D6/2C19/2C9/3A4 tetragenic cluster, more than 80% of the patients exhibit a deficient metabolizer geno-phenotype [3,17]. This evidence concerns the gene CYP2D6 and Alzheimer disease.