title: An in vitro method for predicting in vivo oral bioavailability of novel immunosuppressive drugs.
abstract: OBJECTIVE
  To evaluate an in vitro method for predicting oral availability of novel immunosuppressive drugs, cyclosporine A (CsA) and rapamycin (RAPA).
  
  
  METHODS
  In this study, we report the development and characterization of an in vitro method to study the influence of vehicle composition on cyclosporine A (CsA) and rapamycin (RAPA) drug efflux across 12 days postconfluent, absorptive human Caco-2 intestinal epithelial cell monolayers. The apical-to-basal (Jab) and the basal-to-apical (Jba) fluxes of 0.5 muCi 3H-CsA or 0.05 muCi 14C-RAPA solubilized in a 10 mg/L final drug concentration in vehicle were measured.
  
  
  RESULTS
  The Jab CsA flux was found to be dose dependent, temperature sensitive, and highly polarized (Jab > Jba). For CsA the vehicles were Neoral, Sandimmune, 95% (v/v) ethanol/fetal bovine serum (ethanol/FBS); and for RAPA these were polyethylene glycol/dimethylacetamide (PEG/DMA), polysorbate/Phosal PEG, ethanol/FBS. When Neoral-CsA was tested, the Jab flux of 3H-CsA was the highest and increased almost linearly even after an incubate time of 240 min. The Jab flux of 3H-CsA when Sandimmune-CsA or ethanol/FBS-CsA were used as vehicle was lower and reached a maximal rate by 120 min. In contrast the Jab flux of 14C-RAPA using either PEG/DMA-RAPA or ethanol/FBS-RAPA as vehicle was highest and reached a maximal rate by 120 min, in contrast to the polysorbate/Phosal PEG-RAPA vehicle, which was significantly lower.
  
  
  CONCLUSIONS
  These data are consistent with the pharmacokinetics of these ISD reported in vivo in human patients or in rabbits, using the same vehicles in the oral formulation. As an integral part of drug development, the data presented that an in vitro system as described may be useful in predicting the effect of drug vehicle on absorption in vivo.
authors.affiliation: Department of Laboratory Medicine and Pathology, Faculty of Medicine, The University of Alberta, Edmonton, Canada.
authors.forename: V C
authors.initials: VC
authors.lastname: Dias
authors.forename: R W
authors.initials: RW
authors.lastname: Yatscoff
mesh_terms: D000284:Administration, Oral; D001682:Biological Availability; D001692:Biological Transport; D018938:Caco-2 Cells; D003470:Culture Media; D016572:Cyclosporine / Q000493:pharmacokinetics*; D006801:Humans; D007166:Immunosuppressive Agents / Q000493:pharmacokinetics*; D007408:Intestinal Absorption; D010539:Permeability; D014677:Pharmaceutical Vehicles; D011090:Polyenes / Q000493:pharmacokinetics*; D020123:Sirolimus; D013696:Temperature
chemical_list: D003470:Culture Media; D007166:Immunosuppressive Agents; D014677:Pharmaceutical Vehicles; D011090:Polyenes; D016572:Cyclosporine; D020123:Sirolimus