Cyclosporine pharmacokinetics and blood level monitoring

Although monitoring plasma or whole blood concentrations of cyclosporine has been promoted as a means of limiting toxicity while ensuring adequate immunosuppression, no consensus has been reached with regard to the assay, the specimen to be assayed, the frequency of monitoring, the therapeutic range, or even the necessity of monitoring cyclosporine concentrations. The failure to reach such a consensus can be attributed to a great extent to the complex pharmacokinetic profile of cyclosporine and the inconsistencies in the assay methodology and results used to generate is pharmacokinetic profile. This article places the subject of monitoring cyclosporine concentrations in perspective by reviewing the pharmacokinetics of cyclosporine, the assay methodology, and the published clinical experience with blood level monitoring.