Within-patient variability in immunosuppressive drug exposure as a predictor for poor outcome after transplantation

Within-patient variability in immunosuppressive drug exposure is easily identified by measurement of drug concentrations at the outpatient clinic. Fluctuating levels despite a stable drug dose can be observed in a substantial proportion of patients. It has now been shown that this within-patient variability is a predictor for poor long-term outcome after transplantation. Nonadherence most likely is an important determinant of variability, and strategies to tackle nonadherence are being developed.