Therapeutic dose monitoring of mycophenolate mofetil in dermatologic diseases

Background Mycophenolate mofetil (MMF) is used for prevention of allograft rejection in transplantation medicine. In dermatology it is used as a corticosteroid-sparing agent. The pharmacokinetics of MMF are known to vary by individual. Therapeutic dose monitoring of mycophenolic acid (MPA), the active metabolite of MMF, is used as a guide in transplantation medicine, but limited data exist on the benefit of measuring MPA levels in the management of dermatologic disease. Objective We sought to describe the use of MPA level monitoring in the management of dermatologic disease. Methods We retrospectively searched for cases of patients who were treated with MMF for a dermatologic condition at our tertiary care center, and who had at least 1 trough level measurement of MPA from January 1, 2003, through November 30, 2009. Results Our search identified 24 patients treated with MMF for autoimmune bullous diseases, connective tissue diseases, erythema multiforme, atopic dermatitis, or pyoderma gangrenosum who had at least 1 MPA trough level measured. The range of MPA levels in patients who responded to therapy was 1.2 to 8 μg/mL at a dose range of 1 to 3.5 g/d of MMF. Four cases were analyzed in detail to highlight the use of therapeutic dose monitoring in the management of dermatologic disease. Limitations This was a retrospective study. Conclusion We recommend monitoring MPA levels only in patients not responding to the standard 2-g/d dosage of MMF. MPA levels can help the dermatologist to increase the dose in patients who have poor absorption or to detect therapeutic noncompliance.