Serum albumin level is associated with mycophenolic acid concentration in children with idiopathic nephrotic syndrome.

Mycophenolate mofetil is effective for the treatment of pediatric idiopathic nephrotic syndrome (INS). The dosage of mycophenolate mofetil is adjusted according to the serum concentration of mycophenolic acid (MPA). Kidney function or cyclosporine (CsA) concentrations affect serum MPA levels. However, few studies have focused on the association between serum concentrations of MPA and albumin. This retrospective observational study aimed to evaluate the relationship between the serum concentrations of MPA and albumin in INS children. Subjects were children with INS who underwent the therapeutic drug monitoring of CsA and MPA. We obtained the serum albumin (sAlb) concentration, estimated glomerular filtration rate (eGFR), age, and MPA and CsA areas under concentration–time curves from 0 to 12 h (AUC0–12). Multiple linear regression analysis and generalized estimating equations were performed to predict values for MPA AUC0–12. We obtained information for 51 INS children with 261 MPA AUC0–12 measurements. The standardized regression coefficients of sAlb, eGFR, CsA AUC0–12, and age were 0.54, − 0.21, − 0.07, and 0.04, respectively. Furthermore, MPA AUC0–12 levels positively correlated with sAlb concentrations (p < 0.001) and were inversely correlated with eGFR values (p = 0.005) but not with CsA AUC0–12 (p = 0.24) and age (p = 0.65). Conclusion: Serum albumin concentration was strongly associated with total MPA concentration compared with kidney function or CsA values. Although patients with INS may have a low serum concentration of total MPA in the presence of low sAlb concentration, close attention should be paid to the interpretation of the low MPA values.