title: Intraindividual and interindividual variations in the pharmacokinetics of mycophenolic acid in liver transplant patients.
abstract: The authors evaluated the intraindividual and interindividual variations in the pharmacokinetics of mycophenolic acid after oral administration of mycophenolate mofetil in 10 liver transplant patients. Mycophenolic acid and its metabolite, mycophenolic acid glucuronide, were measured in plasma and urine by high-pressure liquid chromatography. The plasma protein binding of mycophenolic acid was determined by ultrafiltration. The maximum concentration of mycophenolic acid in plasma increased significantly (P < or = .05) with time from 9.1 +/- 7.2 microg/mL (<1 week) to 36.7 +/- 15.6 microg/mL (1 month). The area under the plasma concentration versus time curve of mycophenolic acid also increased significantly with time, from 50.8 +/- 42.1 microg x h/mL to 118.0 +/- 57.6 microg x h/mL (P < or = .05). The plasma protein binding of mycophenolic acid increased from 92% to 98%, and the apparent oral clearance [CL/F] decreased from 32.9 +/- 21.4 L/h during the first study period to 9.0 +/- 4.4 L/h (P < or = .05) during the third study period. The apparent intrinsic clearance of mycophenolic acid did not change significantly over time. The ratio of the area under the curve of mycophenolic acid glucluronide to mycophenolic acid in plasma decreased with time (25.5 +/- 21.2 vs 8.0 +/- 3.3) but did not reach statistical significance. The increased binding of mycophenolic acid to plasma proteins with time after transplantation appeared to contribute to the intraindividual variation, whereas differences in the ability of the liver to metabolize mycophenolic acid between patients appear to contribute to the large interindividual variation in the pharmacokinetics of mycophenolic acid. The observations in this study support the concept of measuring the unbound concentration of mycophenolic acid to optimize immunosuppressive drug therapy with mycophenolic acid.
authors.affiliation: Department of Pharmaceutical Sciences and Pharmacy and Therapeutics, University of Pittsburgh School of Pharmacy, Pittsburgh, PA 15261, USA.
authors.forename: Jaya
authors.initials: J
authors.lastname: Pisupati
authors.forename: Ashok
authors.initials: A
authors.lastname: Jain
authors.forename: Gilbert
authors.initials: G
authors.lastname: Burckart
authors.forename: Imad
authors.initials: I
authors.lastname: Hamad
authors.forename: Sheila
authors.initials: S
authors.lastname: Zuckerman
authors.forename: John
authors.initials: J
authors.lastname: Fung
authors.forename: Raman
authors.initials: R
authors.lastname: Venkataramanan
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D019540:Area Under Curve; D005260:Female; D005965:Glucuronates / Q000493:pharmacokinetics; D020719:Glucuronides; D006084:Graft Rejection / Q000188:drug therapy / Q000378:metabolism*; D006801:Humans; D016031:Liver Transplantation; D008297:Male; D008875:Middle Aged; D009173:Mycophenolic Acid / Q000031:analogs & derivatives* / Q000378:metabolism / Q000493:pharmacokinetics* / Q000627:therapeutic use
chemical_list: D005965:Glucuronates; D020719:Glucuronides; C113145:mycophenolic acid glucuronide; D009173:Mycophenolic Acid