Two cases of delayed cyclosporin absorption leading to CsA exposure higher than that predicted by C2 monitoring alone

Cyclosporin administration designed to achievetarget peak, rather than trough, concentrations is nowroutine practice for many transplant programmes. Thepeak cyclosporin concentration exhibits some degreeof inter-subject variability. However, the concentrationattained2hfollowingtheadministrationofcyclosporinmicro-emulsion (CsA-ME), referred to as C2, is themost consistent peak [1]. Recent trial data have demon-strated the effectiveness of CsA-ME dose adjustmentaccordingtoC2targets,achievingexcellenttolerability,safety and freedom from rejection after kidney [2]and liver transplantation [3].Reliance upon C2 as the sole guide to CSA-MEdosing for an individual patient assumes that thepeak CsA concentration consistently occurs at 2hfollowing ingestion for that individual. Signicantintra-patient variability in time to CsA peak concen-tration may theoretically reduce the reliability of C2monitoring as a surrogate for overall CsA exposure,and hence for clinical outcomes. We present two illus-trativecaseswheretimetopeakCsAconcentrationwasdelayed by intercurrent clinical events, temporarilyrendering C2 an underestimate of overall CsAexposure.