The overexpression of P- glycoprotein (P-gp) is one of the mechanisms of multidrug resistance (MDR), responsible for the failure of cancer treatment. One strategy to restore the effectiveness of the anti-cancer drugs is to co-administer compounds that are not toxic themselves, but inhibit these efflux pumps. These compounds have been called MDR inhibitors, MDR modulators, MDR reversal agents or chemosensitizers...