Mycophenolic acid (MPA), the active form of mycophenolate mofetil (MMF) and enteric-coated mycophenolate sodium (EC-MPS), is used to treat systemic lupus erythematosus (SLE). MMF and EC-MPS pharmacokinetics were examined to devise guidance for therapeutic drug monitoring (TDM) for SLE patients with normal renal function.This observational study included 21 patients receiving MMF (1000 mg twice daily) and 14 taking EC-MPS (720 mg twice daily). MPA AUC between 0 and 12 h (AUC(0-12h)), C(max), T(max), and 12-h trough concentrations (C(12h)) were determined.Means of dose-normalized MMF- or EC-MPS-MPA C(max) were 64.6 +/- 25 and 61.4 +/- 27.1 h mg/l, respectively. MPA T(max) for EC-MPS was longer and more variable than for MMF. MMF-MPA AUC(0-12h) and C(12h) were correlated (r = 0.78, p = 0.0001), but EC-MPS-MPA C(max) and single concentrations were weakly correlated. A limited-sampling strategy (LSS) combining C(max) and C(12h) gave satisfactory predictive performance to estimate MPA AUC(0-12h) after EC-MPS administration.For TDM in SLE patients with GFR > 60 ml/min/1.73 m(2), C(12h) after MMF ingestion could predict MPA AUC(0-12h), while an LSS around T(max) should be used for patients on EC-MPS.