Mycophenolic acid trough level assessment in patients with lupus nephritis; does it make a difference?

Mycophenolate Mofetil (MMF) has become one of the cornerstone treatments of lupus nephritis (LN). It is converted into mycophenolic acid (MPA), an active metabolite, that displays high inter- and intra-individual pharmacokinetic variability. However, the routine monitoring of MPA trough level is still debatable.

The present study aims to evaluate the relationship between MPA trough levels and both clinical outcomes and drug-related adverse effects during the maintenance phase of LN in Egyptian patients.

We included thirty-five adults and twenty-nine children with biopsy-proven class III and IV LN, who had been maintained on steroid and MMF as maintenance therapy for more than six months. Clinical and laboratory markers of lupus activity as well as MMF adverse events were reported. MPA trough levels were measured by High-Performance Liquid Chromatography (HPLC).

There was a significant association between low MPA trough levels and both flares and SLEDAI scores in the adult group (P = 0.027 and 0.019, respectively). Moreover, high MPA trough levels were associated with higher risk of gastritis in the same age group (P = 0.007). There was no significant association with any of the parameters studied in the pediatric group. Gastritis was the most frequent side effect in both age groups.

MPA trough levels correlated with disease activity and gastritis in adult LN patients, and this may help to optimize MMF dosage in these patients. However, MPA concentration-effect relationships were not observed in pediatric patients.