Random pharmacokinetic profiles of EC-MPS in children with autoimmune disease

BACKGROUND: Therapy with mycophenolate mofetil (MMF) has become a valuable therapeutic option in children with autoimmune disease. MMF prescription in children with autoimmune diseases differs from that in transplant recipients in terms of different dosing regimen, and concomitant administration of other immunosuppressive medications. Recently, another formulation of the same active compound, mycophenolic acid (MPA), has become available as enteric-coated Mycophenolate Sodium (EC-MPS). Dosing and pharmacokinetics of EC-MPS in pediatric autoimmune disease have never been studied. METHODS: We therefore performed a pilot study on 6 patients, who were treated with EC-MPS. All patients underwent 1-2 full 10-point pharmacokinetic (PK) profiles over a 12-hour dosing interval. We compared the results with that of 22 similar patients on MMF therapy. RESULTS: Median EC-MPS dose was 724 mg/m(2 )(range 179-933 mg/m(2)). The MPA Area-Under-The-(Time-Concentration)-Curves (AUCs) on MMF and EC-MPS were comparable (54.4 mg × h/L on MMF and 44.0 mg × h/L on EC-MPS, n.s., Mann Whitney). After correcting for bioequivalence, the dose-normalized AUCs were also similar on both the formulations. However, PK profiles on EC-MPS were quite random, and time to maximum concentration varied from 30 minutes to 720 minutes. The concentration at six-hour correlated best with the AUC. This was different from a homogenous PK-profile on MPA. CONCLUSIONS: EC-MPS has a different PK profile from MMF. The data suggest that patients on EC-MPS must undergo a complete PK profile to assess adequate exposure. The 6-hour concentration provides an estimate of the exposure and should be targeted between 3-4 mg/L.