CYP2D6 and Alzheimer disease: Among the CYP variants, CYP2D6 normal metabolizers (NM) tend to be the best responders to treatment, CYP2D6 intermediate metabolizers (IM) show an intermediate response, and CYP2D6 poor metabolizers (PM) and ultra-rapid metabolizers (UM) tend to behave as the worst responders to conventional anti-AD treatments [2,4,6,18,34,35,36,37].