Data from the PAMPA experimental assay (Fig. PAMPA) has a visible peak around logPerm = -4, though higher permeation rates were also measured. This phenomenon is again caused by the abovementioned mixture of apparent and intrinsic PAMPA permeabilities in the literature. Some publications (e.g. refs. ) report the apparent permeability as a direct experimental value of permeation, which is related to CACO-2 permeability. On the other hand, other publications of PAMPA permeation data (e.g. refs. ) report the intrinsic permeability, thus mixing permeability values. As can be seen from the figure, the apparent permeability (light blue) peaks between the values -8 and -4, while the intrinsic permeability (navy blue) is shifted to higher values. However, some values of apparent permeability are over -4 threshold. This phenomenon can be explained by e.g. effort to reduce the UWL layer in permeability assay by increasing of stirring speed . Fujikawa et al present e.g. for Desipramine logPerm = -4.77 (0 rpm), logPerm = -4.00 (200 rpm), and logPerm = -3.81 (250 rpm) .