We show here in a multidrug resistant cancer cell line that over-expresses P-gp, that the continued presence of an inhibitor of P-glycoprotein after a short exposure of the cells to chemotherapeutic in the presence of the inhibitor, and the subsequent removal of the chemotherapeutic from the medium in the presence of the inhibitor, significantly increases the effectiveness of the therapy. Here, ABCB1 is linked to cancer.