No Influence of Everolimus on Mycophenolic Acid Area Under the Concentration-Time Curve: Limited Sampling Strategy for Mycophenolic Acid in Japanese Kidney Transplant Recipients Treated With Tacrolimus, Mycophenolate Mofetil, Steroid, and Everolimus

Background. Despite a growing need for everolimus (EVR) to reduce calcineurin inhibitor toxicity in kidney transplantation (KTx), the influence of EVR on the pharmacokinetics of mycophenolic acid (MPA), a mycophenolate mofetil (MMF) active metabolite, is obscure, and no suitable limited sampling strategy (LSS) for MPA when EVR is concomitantly present exists. We aimed to investigate the influence of EVR on MPA pharmacokinetics in KTx.Materials and Methods. This study complied with all principles of the Declaration of Helsinki. Twenty patients were initially administered tacrolimus, MMF, and methylprednisolone and then received EVR 4 months after KTx. Approximately 4 weeks before and after EVR administration, the estimated value of the area under the concentration-time curve for MPA from 0 to 12 hours (MPA-AUC0-12) was calculated using MPA blood concentration just before and 1, 2, 4, and 6 hours after MMF administration. We compared several MPA pharmacokinetics parameters before and after EVR addition and determined the best estimation equation for LSS of MPA-AUC0-12.Results. Although MPA-C6 per dose (MPA-C6/D) significantly decreased after EVR addition (from 3.4 [+/- 2.2] ng/mL/g to 2.5 [+/- 0.9] ng/mL/g), MPA-C0/D,-C1/D,-C2/D,-C4/D, and MPAAUC0-12/D showed no significant change. MPA-AUC0-12/D did not correlate with EVRAUC0-12/D. The best estimation equation for LSS of MPA-AUC0-12 by 2 time points was [(2.94 x C2) + (5.09 x C4) + 5.32] (R-2 = 0.73) and [(5.70 x C0) + (1.39 x C1) + 22.45] (R-2 = 0.72) before and after EVR addition, respectively.Conclusions. EVR can be safely combined with MMF after KTx once our results have been reevaluated.