Mycophenolate mofetil,an important immunosuppressant drug,is widely used for the prevention of rejection in organ transplants.Although there have been several studies on the effectiveness of therapeutic drug monitoring (TDM) for kidney and heart transplants,there have been few on TDM for MMF in liver transplants.In the present study,blood concentrations of mycophenolic acid (MPA),an active metabolite of MMF,were measured in 56 liver transplant patients treated with the drug at Kumamoto University Hospital since June,2004.Furthermore,a correlation between trough levels and the efficacy and/or adverse effects of MPA was investigated.MPA trough levels tended to be high in patients exhibiting clinical efficacy but intra- and inter-individual variations in trough levels appeared to be very large.The average MPA trough levels for each patient ranged from 0.2-5.8μg/mL.The coefficient of variation in trough levels among individuals was found to be 19-144%.We also investigated a relationship between cytomegalovirus (CMV) infection,a secondary adverse effect of MMF,and MPA trough levels.The anti-virus drug,ganciclovir (GCV) had been given to 19 patients but we found no significant relationship between trough levels and whether patients had been treated with this drug or not.
As the present study did not properly clarify the clinical implications of MPA trough level measurements,detailed investigation of the pharmacokinetics of MMF/MPA in liver transplants and the determinants for intra-/inter-individual variations will be necessary.