Cisapride: a potential model substrate to assess cytochrome P4503A4 activity in vivo.

Objectives: Cisapride was compared with midazolam in vivo to determine its potential applicability as a cytochrome P450 (CYP) 3A4 "probe." As well, we evaluated whether cisapride was transported by P-glycoprotein.

Methods: Bidirectional transport assays were conducted in LLC-PK1 cells and the derivative cell line L-MDR1 to determine whether cisapride was a substrate for P-glycoprotein.