An Isocratic High Performance Liquid Chromatographic Method for Quantification of Mycophenolic Acid and Its Glucuronide Metabolite in Human Serum Using Liquid-liquid Extraction: Application to Human Pharmacokinetic Studies

Background: Mycophenolate mofetil (MMF) is a morpholinoethyl ester of mycophenolic acid (MPA), which is widely used as an immunosuppressive agent in renal transplant patients for the prophylaxis of acute rejection. We describe a fast and sensitive isocratic HPLC method for simultaneous quantification of the immunosuppressant mycophenolic acid, and its major metabolites in human serum.

Methods: The analytes were extracted from serum using ethyl acetate/2 propanol (4-1, v/v) and subjected to an isocratic HPLC method using a phenyl analytical column. A mobile phase consisted of methanol-0.05 mol/l sodium phosphate buffer (46/54 v/v; pH 2.5) containing hexadecyl trimethylammonium bromide (100mg/l w/v) and triethylamine (0.25% v/v) was used.

Results: The standard curve was linear from 0.050 to 51.2 microg/ml and 0.125 to 64 microg/ml, for mycophenolic acid and its metabolite, respectively. The method showed excellent selectivity, specificity, sensitivity, precision and accuracy. The respective limits of quantification for the drug and its metabolite were 0.050 and 0.125 microg/ml. This method was applied in a bioequivalence study following single dose administration of 2 different mycophenolate mofetil preparations in 24 healthy volunteers. Blood samples were analyzed and pharmacokinetic parameters of mycophenolic acid and its metabolite were compared.

Conclusion: This procedure is simple, and comparing to the previously published methods, more sensitivity is obtained and less time is needed for sample preparation. Less time was needed for the liquid-liquid extraction. Although, suitability of the method has been demonstrated in pharmacokinetic studies of MMF in normal subjects, its specificity in renal and hepatic transplant patients has not been established and the stated upper linearity of MPAG may not be sufficient for use in transplant patients.