P-glycoprotein (permeability glycoprotein, P-gp, Pgp, ABCB1, ATP-binding cassette sub-family B member 1, MDR1, and PGY1) is belongs to a subfamily of ABC-transporter called MDR (Classical multidrug resistance). P-glycoprotein functions as a transporter in the blood-brain barrier with a 170 kDa polypeptide. P-gp plays a role in the elimination of drugs and metabolites in kidney and liver, and these cumulative systemic effects would eventuate in lower plasma concentrations of these drugs. P-gp inhibitors can be a kind of anti-cancer drug through reducing multidrug resistance because P-glycoprotein (Pgp), the membrane-associated protein, is overexpressed in tumor cells resulting in an enhanced ability to export drugs from the cell and multidrug resistance.