Compound mixtures in Caco-2 cell permeability screens as a means to increase screening capacity

The purpose of this investigation was a study of simultaneous permeability measurement using compound mixtures (cassette dosing) as an alternative to single compound evaluation in order to increase the capacity of screens for intestinal drug permeability. Drug transport across Caco-2 monolayers was studied, both in the apical to basolateral and the basolateral to apical di rection. The apparent permeability coefficients for ten compounds displayin g different intestinal transport mechanisms were determined. first as singl e compounds and then as components of a mixture. Seven e-adrenoceptor antag onists and baclofen were analysed simultaneously using reversed phase HPLC with UV detection, D-glucose and mannitol were measured by scintillation co unting. The results indicated that the P-app from the mixture as donor phas e correlated well with that of the single compounds and merely small change s in the P-app of each compound were observed between the single compound a nd mixture experiments. This minor variation resulted in a change in rank-o rder of the poorly permeable compounds in the mixture, however, without aff ecting their association with the permeability class according to the bio-p harmaceutics classification system (BCS). It can be concluded that the use of compound mixtures is a suitable method for improving the capacity in per meability screens. Further improvement of the throughput may be expected up on automatisation of permeability measurements using robotics combined with increased selectivity using LC-MS analysis.