Single-dose pharmacokinetics of mycophenolic acid following administration of immediate-release mycophenolate mofetil in healthy Beagle dogs

Mycophenolic acid (MPA) is an immunomodulating agent commonly used in human medicine for the treatment of immune-mediated diseases. There is growing evidence that the immunomodulating properties of mycophenolate mofetil (MMF), a prodrug of MPA, are therapeutically beneficial for the treatment of immune-mediated diseases in dogs. A narrow therapeutic index and high inter-and intra-patient pharmacokinetic (PK) variability complicate the use of MMF. A better characterization of MPA pharmacokinetics is needed to help establish dosing regimens and standardized treatment protocols for canine patients. The purpose of this study was to evaluate the pharmacokinetics of MPA in dogs. MMF oral suspension (10 mg/kg) was administered to five healthy beagle dogs. Serial blood samples were collected from 0 to 18 hours after administration. The simultaneous quantification of MPA, and its metabolites MPA-7-O-glucuronide (MPAG), and acyl glucuronide (AcMPAG) was determined by liquid chromatography (LC)-mass spectrometry (MS)/MS. MPA peak concentrations were achieved rapidly (median Tmax of 0.5 h). Concentrations fell through 3 hours post-dose and then plateaued around 20% of Cmax. The mean elimination half-life was rapid (5.8 hours) and notable variability was observed in all PK parameters. The PK profiles for the MPAG and AcMPAG metabolites followed a similar pattern as MPA concentration. Future repeat-dose studies will be needed to evaluate steady-state PK parameters and to define therapeutic MPA dose levels.