The present invention relates to efflux inhibitor compounds, compositions, and methods of using the same. More specifically, the instant invention comprises deuterated analogs of elacridar with superior pharmacokinetic properties such that it is now possible to facilitate accumulation and distribution of therapeutic agents to effective levels in cells or compartments protected by efflux transporter proteins such as Breast Cancer Resistance Protein (BCRP) and P-Glycoprotein (P-GP). Such transporter protected compartments include brain, spinal cord, nerves, cerebrospinal fluid, testis, eyeballs, retina, inner ear, placenta, mammary gland, liver, biliary tract, kidney, intestines, lung, adrenal cortex, endometrium, hematopoietic cells, stem cells, and solid tumors. In other embodiments, the present invention comprises methods of using the instant deuterated analogs.
