Substituting for and replacing the older and more primitive, 2-well subtractive sandwich culture model, the Hµrelflux™ biliary efflux assay method is additive, separately measuring the amount of sample that is taken up and retained by the hepatocyte, that is secreted directly to the plasma, and that is excreted to the biliary system.  Conducting the entire assay in a single microtiter well dramatically reduces assay costs and minimizes the signal-to-noise liabilities of the two-well sandwich culture method, precluding the possibility of generating negative biliary excretion indices (BEI’s).  IVIVC of Hµrelflux™ has been measured as superior to that of published literature data on the sandwich culture method. Hµrelflux™ biliary efflux assays kits include all necessary media including canalicular tight junction disruption media.