Permeabilities measured by the BLM/liposome method are typically higher than -4, likely due to the relatively large membrane area in liposomal systems. Although the BLM/liposome method also provides apparent permeabilities, the UWL, in this case, is significantly smaller than that of CACO-2, MDCK or PAMPA, and its contribution is practically negligible. The lowest experimentally measured permeability value is -13.1 log units for saccharose from Brunner et al. . Its authors say that any value lower than -10 log unit is hardly measurable.