Usefulness of cyclosporine levels one to six months posttransplant.

CsA levels are definitely useful for monitoring patients one to six months post-renal transplantation. They help to document that individuals are complying with their medication therapy and taking the medication. They may identify patients who are not absorbing the drug due to associated gastrointestinal problems. There is a correlation, although weak, with both rejection and nephrotoxicity. A variety of other factors may limit the usefulness of this correlation, but serial measurements of the CsA trough level will help when making clinical decisions for these patients. Finally, monitoring of CsA levels will help to identify drug interactions and to determine quantitatively the impact of these interactions. Thus, a more appropriate dosage modification of CsA can be determined because of the availability of specific drug levels. Pharmacokinetic modeling may be useful to assess variability in absorption and metabolism of the drug in individual patients. The practical usefulness of this technique, however, remains less clear due to its expense and inconvenience.