Plasma Mycophenolic Acid Determination by Ultra-high Performance Liquid Chromatography-tandem Mass Spectrometry and Its Application in Pediatric Patients with Nephrotic Syndrome

Objective: Mycophenolate mofetil (MMF) is frequently prescribed to pediatric patients with nephrotic syndrome (NS); however, information on the active metabolite mycophenolic acid (MPA) in this population is limited. Method: Using ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS), we validated a rapid and simple approach to measure MPA in accordance with the Bioanalytical Method Validation Guidance issued by the relevant regulatory authorities. Statistical analyses were performed on 69 pediatric patients with frequently relapsing/steroid-dependent nephrotic syndrome (FRNS/SDNS) who received corticosteroids plus MMF. Results: Forty-two patients achieved the endpoints and reported adverse events (AEs). The area under the concentration–time curve of MPA in the AE group was further distributed. Monitoring blood MPA concentrations is critical to prevent AEs during MMF administration in children with FRNS/SDNS. Conclusion: UHPLC–MS/MS offers a more accurate reference than immunoassays.