Immunosupressant drug monitoring - recent innovations with emphasis on cyclosporine

Abstract

Despite some 20 years of therapeutic drug monitoring (TDM) of cyclosporine (CsA), there are new directions in both the clinic and laboratory that require a critical review of practices to optimise the clinical care of our organ transplant recipients. These changes include alternatives to pre-dose (C 0) blood sampling, in favour of abbreviated area under the curve strategies, or alternative single-point sampling such as 2-hours after the dose (C2). These new monitoring practices have necessitated a review of existing assay methods as they are associated with CsA concentrations which exceed the calibration limits for many commercial CsA immunoassays, necessitating dilution in the TDM laboratory that have proved problematic. The most widely used methods have poor specificity in terms of measuring the target analyte, parent CsA, without clinically significant cross-reactivity with CsA metabolites. This raises questions about the method selection criteria of many TDM laboratories. Monitoring the newer immunosuppressant drugs (tacrolimus, mycophenolate, sirolimus) is also reviewed.