Nephrotic state substantially enhances apparent mycophenolic acid clearance


Area of Science:

• Pharmacokinetics
• Nephrology
• Immunosuppression

Background:

• Several factors can decrease mycophenolic acid (MPA) plasma protein binding and increase its clearance.
• Dose adjustments for mycophenolate mofetil (MMF) in steroid-resistant nephrotic syndrome (SRNS) are not well-established.
• Therapeutic drug monitoring of MPA is not routinely used for SRNS.

Purpose of the Study:

• To investigate the relationship between MPA apparent clearance and various clinical parameters in pediatric SRNS patients.
• To determine if MPA underexposure contributes to MMF unresponsiveness in SRNS.

Main Methods:

• Retrospective cohort study of 10 pediatric SRNS patients treated with MMF.
• Measured 182 MPA predose trough levels using HPLC/MS/MS.
• Calculated apparent MPA clearances (CL/F) and analyzed correlations with albumin, proteinuria, triglycerides, and eGFR.

Main Results:

• Median apparent MPA clearance was 22.63 L/h.
• Significant correlations found between MPA CL/F and serum albumin (negative), microalbuminuria (positive), triglycerides (positive), and cholesterol (positive).
• MPA CL/F increased substantially with lower albumin levels (< 25 g/L) and higher triglycerides.

Conclusions:

• Increased MPA clearance in SRNS is significantly associated with low albumin, proteinuria, and high triglycerides.
• A 20-fold increase in apparent MPA clearance suggests MPA underexposure may cause MMF unresponsiveness in nephrotic states.
• Further investigation into MMF dosing and therapeutic drug monitoring in SRNS is warranted.