Comparison of Inosine-Monophosphate-Dehydrogenase Activity in Patients With Enteric-Coated Mycophenolate Sodium or Mycophenolate Mofetil After Renal Transplantation

Background. Mycophenolate mofetil (MMF) and enteric-coated mycophenolate sodium (EC-MPS) are well established in immunosuppressive therapy after renal transplantation. The active substance, mycophenolic acid, leads to an inhibition of inosine-monophosphate-dehydrogenase (IMPDH) activity in peripheral mononuclear cells. Therefore, we analyzed the effect of different dosing patterns of MMF and EC-MPS on IMPDH activity in stable patients after renal transplantation. Methods. IMPDH activity (pmol/s per pmol AMP) was measured in patients in the maintenance phase after renal transplantation. Besides MMF or EC-MPS, immunosuppressive therapy consisted of calcineurin inhibitor with or without steroids. We performed 260 measurements in 110 patients (82 on MMF, and 28 on EC-MPS). Results. Mean patient age range of 43 women and 67 men was 22 to 74 years. Mean serum creatinine in the MMF group was 1.7 +/- 1.3 mg/dL compared to 1.48 +/- 0.45 mg/dL in the EC-MPS group (P < .05). The median IMPDH activity in the EC-MPS patients was lower than in the MMF patients (10 vs 24 pmol/s pmol AMP; P < .005). This was especially pronounced in patients on 1440 mg/d EC-MPS compared with 2000 mg/d MMF (P < .001). Conclusion. Measurement of IMPDH activity in renal transplantation patients adds additional information on the degree of immunosuppression. The inhibition of IMPDH activity with EC-MPS seemed more pronounced than MMF despite formally equipotent doses.