Significance of mycophenolate monitoring in liver transplant recipients: toward the cut-off level.

Mycophenolate mofetil blocks the "de novo" -purine synthesis to reduce the incidence and severity of acute rejection episodes. There has been an increased interest in utility of monitoring mycophenolic acid (MPA) levels, however currently the MPA monitoring is not part of the protocol following liver transplantation. We assessed whether trough MPA monitoring could be advisable in liver transplant patients or not. For this reason MPA levels of 56 liver transplants were measured on 3, 5, 10, 14, 21, 30, 60, and 180 posttransplant days. The optimal cut-off of MPA level (≥1.73 mg/L) for all (56) and ≥1.34 mg/L for ciclosporin-treated- and ≥1.98 mg/L for the tacrolimus-treated transplants were calculated by statistical analysis to reduce the incidence of acute rejection. MPA concentrations of 3 days period before the day of clinical diagnosis acute rejection were well below the cut-off value. Only 3 (16%) out 19 patients with acute rejection had higher MPA levels than the cut-off value on the day of diagnosis of acute rejection. In conclusion, our data suggests that MPA predose level monitoring, especially in the early "filling phase" after transplantation, is applicable in liver allograft recipients given adjunctive MMF, protecting them from the ineffective immunosuppression.