Abstract
<title>Abstract</title> <p>Background For mycophenolate mofetil (MMF) maintenance therapy in patients with frequently relapsing idiopathic nephrotic syndrome (INS), the targeted exposure of the active metabolite mycophenolic acid (MPA-AUC) should exceed 50 mg×h/L. Therefore, therapeutic drug monitoring has been recommended. We analyzed whether this target MPA-AUC is achieved with a standard MMF dose during initial INS treatment. Methods After achieving remission, children with an initial manifestation of steroid-sensitive INS received MMF at a dose of 1,200 mg/m² body surface area per day for a total treatment duration of 12 weeks. Pharmacokinetic MPA data were obtained from 69 patients (median age 4.00 years (IQR, 3.00–5.00), 26.1% female) at week 4 after MMF treatment initiation of and at week 12 at the end of the initial treatment period. Results Patients exhibited median MPA-AUC values of 77.9 (IQR, 53.0-107) mg×h/L and 81.6 (IQR, 54.6–102) mg×h/L at weeks 4 and 12, respectively. 81.3% (N = 52/64) of patients achieved an MPA-AUC > 50 mg×h/L at week 4 and 85% (N = 50/59) achieved this level at week 12. No association was observed between MPA-AUC at week 12 and the occurrence of treated or frequent relapses during the two-year study period. Conclusions During the initial treatment of INS with MMF, the recommended MPA exposure for long-term treatment is achieved in most patients and does not appear to influence the subsequent course of INS. Therefore, therapeutic drug monitoring of MMF during the initial treatment of INS does not appear to be necessary.</p>