PGP and neoplasm: Drug efflux is caused by adenosine triphosphate (ATP)‐binding cassette drug transporters especially P‐glycoprotein (P‐gp) that are overexpressed on the cancer cell membrane,11, 12, 13 which transports the chemotherapeutics to the extracellular matrix, causing the drug concentration to decrease below its therapeutic threshold and attenuate the cytotoxic drug response on tumor cells.10, 14, 15