Changes in AD regarding this aspect are determined by the properties of the BBB, CSF reabsorption, brain blood flow, and P-glycoprotein 1 (P-gp) permeability, known as the multidrug-resistance protein 1-P-gp, also known as multi-drug resistance-associated protein 1-P-gp; these changes are the most studied, and some of these effects will continue to increase while others decrease the balance of medication inside the brain. Here, PGP is linked to Alzheimer disease.