Gastrointestinal malabsorption is a common complication of CF that can affect the impact of immunosuppression. It has been shown that CF patients can have sub-therapeutic calcineurin inhibitors.6,7 However, little information regarding MMF pharmacokinetics (PK) exist in this population. One small observational study of 30 stable lung-transplant recipients demonstrated that the CF patients (n=7) required at least 30% higher doses to achieve similar pre-dose levels of mycophenolic acid (MPA) to that of non-CF patients (n=6).8 The authors did not include any other PK parameters in their results. In a second study, 12-hour PK of MPA and its glucuronide metabolites were characterized in 21 stable lung transplant recipients. The authors included 5 CF patients and found no significant difference in PK parameters except for the ratio of MPA glucuronide and MPA (MPAG/MPA) between the CF and non-CF patients. However, the CF patients tended to have a lower area under the curve (AUC) than non-CF patients. Inter- or intra-patient variability of MPA AUC was not determined in this study.9 In addition, these previous studies did not distinguish tacrolimus-based regimen from cyclosporine-based regimen.