Mycophenolate mofetil in patients with anti‐neutrophil cytoplasmic antibody‐associated vasculitis: a prospective pharmacokinetics and clinical study

Summary Anti‐neutrophil cytoplasmic antibody‐associated vasculitis ( AAV ) treatment strategy is based on immunosuppressive agents. Little information is available concerning mycophenolic acid ( MPA ) and the area under the curve ( AUC ) in patients treated for AAV . We evaluated the variations in pharmacokinetics for MPA in patients with AAV and the relationship between MPA–AUC and markers of the disease. MPA blood concentrations were measured through the enzyme‐multiplied immunotechnique ( C 0, C 30 , C 1 , C 2 , C 3 , C 4 , C 6 and C 9 ) to determine the AUC . Eighteen patients were included in the study. The median (range) MPA AUC 0–12 was 50·55 (30·9–105·4) mg/h/l. The highest coefficient of determination between MPA AUC and single concentrations was observed with C 3 ( P  < 0·0001) and C 2 ( P  < 0·0001) and with C 4 ( P  < 0·0005) or C 0 ( P  < 0·001). Using linear regression, the best estimation of MPA AUC was provided by a model including C 30 , C 2 and C 4 : AUC  = 8·5 + 0·77 C 30  + 4·0 C 2  + 1·7 C 4 ( P  < 0·0001). Moreover, there was a significant relationship between MPA AUC 0‐12 and lymphocyte count ( P  < 0·01), especially CD 19 ( P  < 0·005), CD 8 ( P  < 0·05) and CD 56 ( P  < 0·05). Our results confirm the interindividual variability of MPA AUC in patients treated with MMF in AAV and support a personalized therapy according to blood levels of MPA .