Some reports have indicated that the blood concentration of most generic drugs is difficult to maintain stableility, and it may cause the difference in graft survival or nonsurvival of transplanted organs between original drugs and generic drugs. In this article, we report two cases that could not maintain blood concentration of generic drugs of mycophenolate mofetil (MMF).
Case 1: A nineteen-year-old patient. At the day of transplantation, MMF was changed to a generic drug. We found that the serum creatinine level was increased to 1.22 mg/dl at postoperative day 24. The plasma concentrations before the conversion of MMF was subthreshold. Therefore we changed the generic drug to the original drug. After that, the plasma concentration of MMF was increased to 2.4 μg/ml, and serum creatinine level was also improved to 0.96 mg/dl.
Case 2: An eight-year-old boy. He had continued diarrhea and was admitted to a hospital for general care. At that time, MMF was changed to a generic drug. The plasma concentrations of MMF were rapidly decreased to 0.6 μg/ml on the sixth day after admission. When the generic drug was changed to the original drug, it was increased again, to 3.7 μg/ml.
Conclusion: Some reports have indicated that a failure to maintain plasma concentration of MMF leads to rejection. Therefore maintenance of effective plasma concentration and prevention of rejection are essential to long-term graft survival in kidney transplants. In both cases, we discontinued use of the generic drugs thereafter because of unstable plasma concentrations of MMF.
Conversion to the generic drug may cause differences in effects and absorption. If the generic drug should be used patients should be closely monitored.