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. The gene discussed is ABCB1; the disease is Alzheimer disease.