Therapeutic drug monitoring for mycophenolic acid in patients with autoimmune diseases.

Mycophenolate mofetil (MMF, CellCept R © ) has become the most frequently used immunosuppressive drug in kidney transplant recipients [1]. Since its approval for the prevention of acute rejection after kidney transplantation in 1995 in the USA and in 1996 in Europe, the use of azathioprine has been rapidly diminishing, giving way to the use of MMF. A second formulation of mycophenolic acid (MPA), the active metabolite of MMF, has become available as enteric-coated mycophenolate sodium (EC-MPS, Myfortic R ©). Randomized clinical trials have shown that EC-MPS 720 mg b.i.d. is therapeutically equivalent to MMF 1000 mg b.i.d. with a comparable safety profile [2,3]. These equimolar doses of EC-MPS and MMF produce equivalent MPA exposure. The delayed release formulation, EC-MPS, exhibits more variable pre-dose MPA concentrations and more variable peak concentrations [4]. Because of the favourable experience with MMF in transplant recipients, combining good efficacy with relatively few side effects, its use has also been tried in patients with autoimmune diseases [5]. Following case reports and case series of the successful use of MMF, controlled trials have been started [6]. Increasing evidence suggests that MMF can be used not only for the prevention of rejection in solid organ transplant recipients, but also for the treatment of several immunologically mediated (renal) diseases [7].