Influence of renal insufficiency on pharmacokinetics of ACYL-glucuronide metabolite of mycophenolic acid in renal transplant patients.

The acyl glucuronide of mycophenolic acid (AcMPAG) is a metabolite with in vitro immunosuppressive activity. The chemical properties of acyl glucuronides have been associated with the toxicity of some drugs. The aim of our study was to analyze the influence of renal insufficiency on the pharmacokinetics of AcMPAG. Areas under the 12-hour curve (AUC(0-12h)) of MPA, glucuronide of MPA (MPAG), and AcMPAG were determined by high performance liquid chromatography performed in 20 renal transplantation patients under treatment with mycophenolate mofetil (MMF), cyclosporine, and steroids. They were divided between a group with preserved renal function (group I, mean creatinine clearance [Clcr] of 105 +/- 7 mL/min) and one with advanced renal insufficiency (group II, mean Clcr of 27 +/- 5 mL/min). There was no difference in MMF dose or MPA-AUC(0-12h) values between groups. Mean predose levels of AcMPAG-C0 and AcMPAG-AUC(0-12h) were much higher in group II than in group I (0.5 +/- 2 vs 1.6 +/- 1 microg/mL and 12 +/- 2 vs. 32 +/- 19 microg*h/mL respectively, P < .005). The present data suggested that AcMPAG, a metabolite with immunosuppressive activity that may be related to toxic effects of MPA, is renally eliminated. Its levels can significantly rise in patients with renal insufficiency. Although further studies with more patients are required to determine the role of AcMPAG in MPA toxicity, we believe that this accumulation may be of clinical relevance.