Impact of Fasting Status and Circadian Variation on the Pharmacokinetics of Mycophenolate Mofetil and the Glucuronide Metabolite in Renal Transplant Recipients

Mycophenolate mofetil (MMF) is an immunosuppressive prodrug often used to prevent allograft rejection following solid organ transplantation. After oral administration, MMF is rapidly hydrolyzed to the active metabolite mycophenolate acid (MPA), which is inactivated by glucuronosyltransferase to the mycophenolic acid glucuronide metabolite (MPAG). The aim was 2-fold: to investigate the impact of circadian variation and fasting versus nonfasting status on MPA and MPAG pharmacokinetics in renal transplant recipients (RTRs). METHODS. RTRs with stable graft function treated with tacrolimus, prednisolone, and MMF (750 mg BID) were included in this open, nonrandomized study. Two 12-h pharmacokinetic investigations were conducted in succession following morning and evening doses, both in a fasting and in a real-life nonfasting condition. RESULTS. A total of 30 (22 men) RTRs performed one 24-h investigation, and 16 repeated the investigation within 1 mo. In a real-life nonfasting state, MPA area under the curve (AUC)(0–12) and C(0) failed to meet the bioequivalence criteria. Following the evening dose, mean MPA AUC(12–24) was 16% lower (P < 0.001) compared with AUC(0–12), and a shorter T(max) was observed (P = 0.09). Under fasting conditions, MPA AUC(12–24) was 13% lower than AUC(0–12), and the absorption rate was slower after the evening dose (P < 0.05). MPAG displayed circadian variation only under real-life conditions with lower AUC(0–12) following the evening dose (P < 0.001). CONCLUSIONS. Both MPA and MPAG showed circadian variation with somewhat lower systemic exposures following the evening dose with limited clinical relevance in the dosing of MMF in RTRs. Fasting status affects MMF absorption rate differently, but with similar results in systemic exposure.