ABCB1 and Alzheimer disease: Nowadays, R-[11C]verapamil isomer is being used for the evaluation of the blood-brain barrier function in aging and AD, since its high uptake as radiotracer indicates decreased P-glycoprotein functionality in these conditions (Luurtsema et al., 2003; van Assema et al., 2012b; Chai et al., 2019).