Twelve-month evaluation of the clinical pharmacokinetics of total and free mycophenolic acid and its glucuronide metabolites in renal allograft recipients on low dose tacrolimus in combination with mycophenolate mofetil.

BACKGROUND

The establishment of a rationale for therapeutic drug monitoring for mycophenolic acid (MPA) and outlining a therapeutic window remains a challenging task in renal transplantation. Furthermore, the pharmacokinetic characteristics of free and total MPA and its glucuronides depend directly or indirectly on graft function and the type of co-administered calcineurin-inhibitor.

METHODS

The authors conducted a prospective 12-month multicenter pharmacokinetic study on MPA (MPA, free MPA, free fraction MPA) and its metabolites (MPAG, Acyl-MPAG). The aim of this study was to examine the long-term pharmacokinetic characteristics of MMF when combined with tacrolimus in renal allograft recipients and to identify a possible relationship between these pharmacokinetic parameters and clinical outcome parameters.

RESULTS

They have demonstrated that in renal transplant recipients MPA, free MPA, Acyl-MPAG and MPAG have a particular pharmacokinetic profile when combined with tacrolimus which differs from the combination with CsA. They could not establish a relationship between pre-dose trough concentration of MPA and its metabolites and clinical efficacy endpoints and drug-related adverse events, except for anemia.

CONCLUSIONS

These findings suggest that trough plasma concentration monitoring of MPA and its metabolites might not provide a useful clinical tool for guiding MMF dose adjustments to avoid drug-related toxicity. More extensive pharmacokinetic measurements like area under the concentration curves might be necessary for routine therapeutic drug monitoring of MMF.