Imaging P‐Glycoprotein Function at the Blood–Brain Barrier as a Determinant of the Variability in Response to Central Nervous System Drugs

P-glycoprotein (P-gp) is an efflux transporter expressed at the blood-brain barrier (BBB), which restricts the brain distribution of many drugs.Variability in P-gp function at the BBB may lead to variability in response to central nervous system (CNS)-acting drugs and/or CNS adverse effects.Positron emission tomography (PET) with radiolabeled P-gp substrates has opened up the possibility to directly study P-gp function at the human BBB.Yet, the role of P-gp in governing the response to CNS drugs has remained elusive so far.