In vitro permeability of eight beta-blockers through Caco-2 monolayers utilizing liquid chromatography/electrospray ionization mass spectrometry.

It is demonstrated that the apparent permeability (P(app)) coefficients of beta-adrenoceptor antagonist drugs can easily be determined for Caco-2 cell culture intestinal models utilizing liquid chromatography/mass spectrometry (LC/MS). The LC/MS method with electrospray ionization in the single ion monitoring mode showed an increased sensitivity of 1000-fold compared with LC/UV detection and enhanced selectivity with respect to both LC/UV and radioactivity assays. The P(app) coefficients of beta-adrenoceptor antagonists determined by LC/MS have the same ranking order as those determined by LC/UV and radioactivity assays. However, the P(app) coefficients determined in this study showed significant discrepancies from those determined in other laboratories. There are several experimental factors that directly affect the absolute value of the P(app) coefficients, including pH gradients, additional diffusion barriers (i.e. unstirred water layer and type of filter support), analyte concentration, detection method and possibly cell culture variations. These parameters should be controlled when generating Caco-2 P(app) coefficients for different compounds.