Therapeutic monitoring of mycophenolic acid in renal transplanted patients by a validated HPLC method

Introduction: Mycophenolate mofetil and its active metabolite mycophenolic acid are routinely used as immunosuppressant drugs in solid organ transplantation in a fixed daily dose regimen in association with cyclosporine, tacrolimus and steroids. Therapeutic drug monitoring for mycophenolic acid concentration has been suggested to optimize outcomes by reducing rejection and drug related toxicities in clinical renal transplantation.Aim: To determine the predose concentration of mycophenolic acid in renal transplanted patients by a validated proposed high-performance liquid chromatography (HPLC) method and to estimate the interindividual variability based on the therapeutic target.Materials and methods: An HPLC method combined with protein precipitation has been validated for mycophenolic acid determination in the human plasma obtained from 21 renal transplant recipients. HPLC analysis was carried out using the chromatographic system Agilent Technologies 1200 DAD. Samples were injected manually, and the compounds were separated on a LiChrosphere® select B C18 analytical column. The mobile phase was 45:55 (v/v) acetonitrile-buffer phosphate, pH 2.5, flow rate of 1.0 mL/min and column temperature of 30°C. Detection was performed at 215 nm. Whole blood samples were collected into vacutainers containing EDTA and separated at 6000 g for 10 minutes. A 200-μL aliquot of patient plasma was transferred to a tube, followed by addition of 10 μL of naproxen as internal standard and 400 μL of acetonitrile (v/v) as a protein precipitating agent. Each tube was vortex-mixed for 30 sec and then centrifuged for 10 min at 10000 rpm. 20 μL of the supernatant was injected into the HPLC system for analysis.Results: The method showed appropriate linearity for MPA with correlation coefficient greater than 0.999. High inter-patient variability is observed with 18% of patients within the target trough concentration range, 27% of patients below the target trough concentration range and 54% over the range with risk of toxicity.Conclusions: Therapeutic monitoring of MPA might contribute to a better management of renal transplant recipient with the goal of optimizing therapeutic regimens in order to reduce the risk of rejection and MPA‐related toxicity