[ SP 18 sp F]MC225 is a weaker P-gp substrate and has shown higher brain uptake than I (R)- i [ SP 11 sp C]verapamil at baseline in preclinical studies [[2]]. P-glycoprotein (P-gp) is an ATP-dependent efflux transporter located at the blood-brain barrier (BBB), involved in the transport of a variety of neurotoxic substances out of the brain. Evaluation of P-glycoprotein function at the blood-brain barrier using [18F]MC225-PET.