It is interesting, however, to compare the pharmacokinetics of a known P-glycoprotein inhibitor, tariquidar, in human plasma after an intravenous injection of a 150 mg dose in a Phase I study [43] with the pharmacokinetics of doxorubicin in an unrelated study in women undergoing chemotherapy for breast cancer [44]. This evidence concerns the gene ABCB1 and breast cancer.