Investigation of the Association Between Total and Free Plasma and Saliva Mycophenolic Acid Concentrations Following Administration of Enteric-Coated Mycophenolate Sodium in Adult Kidney Transplant Recipients.

Background And Objectives: Mycophenolic acid (MPA) is commonly used following renal transplant. Saliva MPA concentrations may reflect the pharmacologically active form of MPA in plasma. Therapeutic drug monitoring using saliva is convenient and non-invasive. This study examined the correlation between total and free plasma and saliva MPA concentrations following enteric-coated mycophenolate sodium (EC-MS) administration in renal transplant recipients.

Methods: Total and free plasma and saliva MPA concentrations were measured simultaneously in 20 adult renal transplant recipients 1-2 months' post-transplant. Thirteen samples were taken pre-dose and at specified time points up until 12 h post-dose.

Results: When considering all time points, correlation between total plasma and saliva MPA was r = 0.51 and between free plasma and saliva MPA concentrations r = 0.41. The correlation between total plasma MPA area under the concentration-time curve (AUC) or free plasma AUC and saliva MPA AUC was r = 0.25 and r = 0.13, respectively. The correlation between total plasma MPA AUC and total plasma MPA trough (C) concentrations was r = 0.51, and between total plasma MPA AUC and saliva MPA trough concentrations, r = 0.03.

Conclusions: Measurement of MPA concentration in saliva cannot currently replace plasma measurement for therapeutic drug monitoring of MPA following EC-MS administration. Additional studies are required to examine the relationship between MPA saliva concentrations and patient outcomes.