Background: The calcineurin inhibitor tacrolimus (Tac) is an integral part of the standard immunosuppressive
regimen after renal transplantation (RTx). However, clinical management of Tac therapy can be challenging
because of its narrow therapeutic window and because many factors interfere with its metabolism. Therefore, therapeutic
drug monitoring is used to adjust the dosage.
Method: Recently, we were able to classify patients receiving tacrolimus into two major metabolism groups by simple
calculation of the C/D ratio (expressed as the blood concentration normalized by the dose).
Results: We showed that the C/D ratio is significantly associated with the (renal) outcome of recipients after kidney
and liver transplantation.
Conclusion: These findings are interesting and relevant to transplant physicians and physicians interested in immunosuppressive
therapy. We therefore review current state of the art aspects of tacrolimus pharmacokinetics including
genetics or different tacrolimus formulations (twice-daily immediate-release tacrolimus capsules, once-daily extended-
release tacrolimus capsules; novel once-daily tacrolimus tablets) and their possible clinical impact including
practical considerations for clinicians.