Mycophenolate mofetil levels in stable kidney transplant recipients

The usefulness of mycophenolate mofetil (MMF) levels in stable kidney transplant patients is not well known. We measured MMF trough levels in 137 adult kidney recipients with more than 1 year of stable graft function. The MMF dose was adjusted according to hematological or gastrointestinal toxicity, it was 500 mg in 22 (16%) patients; 750 mg in 22 (16%); 1000 mg in 69 (50.5%); 1500 mg in 15 (11%); and 2000 mg in 9 (6.5%). We analvzed the total dose, virgule dose/kg, and MMF levels in relation to efficacy parameters (creatinine, proteinuria) and hematological toxicity (erythrocytes, leukocytes, and platelets) at the time of MMF level determinations and 3 months thereafter. Statistical analyses were performed with SSPS 12.0, including sensitivity and specificity analyses by ROC. Mean MMF levels were 3.68 mg/L (Pc25, 1.6-Pc75, 4.4 mg/L) with significant differences according to dose (P < .001). Trough MMF levels did not have discriminatory capacity in the area under the ROC for anemia, renal failure, or proteinuria at the time of determination or 3 months later. The percentage of patients without proteinuria was high among patients with MMF levels between 1.6 and 4.4 mg/L. The MMF levels were low in patients who had a major increase in creatinine (1.6 vs 3.8 mg/L, P < .05). In stable renal transplant patients the levels of MMF were related to the administered dose, and they are higher than those previously described in patients with less than a year follow-up with a functioning kidney. They did not have discriminatory value at the time of determination or 3 months later. Nevertheless, low MMF levels could help recognize patients at risk of developing chronic nephropathy.