Pharmacokinetic basis for the efficient and safe use of low-dose mycophenolate mofetil in combination with tacrolimus in kidney transplantation.
BACKGROUND
Mycophenolate mofetil (MMF) is an effective posttransplantation immunosuppressive agent used in combination with cyclosporin A (CsA) or tacrolimus (Tc). An increase in plasma mycophenolic acid (MPA) has been shown in patients receiving Tc-MMF combination therapy compared with CsA-MMF combination therapy at the same dose of MMF. The aim of this prospective study was to assess the pharmacokinetic/pharmacodynamic (PK/PD) relationship for MPA in kidney transplant patients receiving low-dose MMF (500 mg twice a day) in combination with Tc.


METHODS
Adult kidney transplant recipients (n = 51) were included. MPA-PK profiles (blood sampling at 0, 0.5, 1, 2, 4, 6, and 12 h after MMF oral dose) were obtained within the first 2 weeks after transplantation, 3 months after grafting, and at every adverse clinical event [side effect or acute rejection (AR)]. All patients received Tc, MMF (500 mg twice a day), and steroids.


RESULTS
Thirty patients (59%) had uneventful outcomes, and 21 patients had 33 episodes of MPA-related side effects; only 3 patients had AR. A total of 78 MPA-PK profiles were obtained. The following PK parameters were increased in the side-effects group compared with the non-side effects group: mean MPA c(min), 2.63 +/- 1.58 vs 1.75 +/- 0.82 mg/L (P = 0.016); mean c(30), 10.47 +/- 6.27 vs 7.66 +/- 8.95 mg/L (P = 0.009); mean c(60), 9.67 +/- 5.42 vs 5.83 +/- 2.6 mg/L (P = 0.0002); mean area under the MPA time-concentration curve from 0 to 12 h [MPA-AUC((0-12))], 48.38 +/- 18.5 vs 36.04 +/- 10.82 mg. h/L (P = 0.0006); mean dose-normalized MPA-AUC, 0.16 +/- 0.05 vs 0.12 +/- 0.04 (mg. h/L)/(mg/m(2)) (P = 0.0015). For the three AR patients, MPA concentrations obtained at the time of AR revealed MPA c(min) values of 1.86, 1.76, and 3.83 mg/L, respectively, and MPA-AUC((0-12)) values of 37.7, 24.9, and 104.9 mg. h/L. The threshold of toxicity was 3 mg/L (sensitivity, 38.7%; specificity, 91.5%) for c(min), 8.09 mg/L for maximum MPA concentration during the first hour (sensitivity, 77.8%; specificity, 67.4%), and 37.6 mg. h/L for MPA-AUC((0-12)) (sensitivity, 83.3%; specificity, 59.6%).


CONCLUSIONS
These results demonstrate the relationship between plasma MPA concentrations and toxicity. High c(min), c(30), and c(60) values as well as AUC((0-12)) are associated with increased risk for side effects. These values may have an importance in a routine monitoring program.
Mourad
M
M
Department of Kidney and Pancreas Transplantation, University Hospital Saint Luc, Université Catholique de Louvain, Avenue Hippocrate 10, 1200 Brussels, Belgium. Michel.Mourad@chir.ucl.ac.be
Malaise
J
J
Chaib Eddour
D
D
De Meyer
M
M
König
J
J
Schepers
R
R
Squifflet
J P
JP
Wallemacq
P
P
D000328:Adult; D004334:Drug Administration Schedule; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D007166:Immunosuppressive Agents / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D009173:Mycophenolic Acid / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives / Q000493:pharmacokinetics* / Q000494:pharmacology; D011446:Prospective Studies; D012372:ROC Curve; D016559:Tacrolimus / Q000008:administration & dosage / Q000009:adverse effects / Q000493:pharmacokinetics* / Q000494:pharmacology
D007166:Immunosuppressive Agents; D009173:Mycophenolic Acid; D016559:Tacrolimus