The need of mycophenolic acid monitoring in long-term renal transplants.

:  Background:  There is little information regarding the 12-h mycophenolic acid (MPA) pharmacokinetics (PK), a way to monitor the drug and the need of frequent monitoring, in stable patients. Methods:  A cohort of 35 adults, under long-term mycophenolate mofetil (MMF) therapy plus cyclosporin A (n = 12), TACimus (n = 12) or MMF only (n = 11); all with prednisone had a 12-h MPA-PK performed to ascertain the percentage of them within a defined therapeutic window. In 13 other patients, two PK studies undergone 1 wk apart were performed to evaluate the need for frequent measurements. Results:  Fourteen (40%) patients were within the defined therapeutic window (36–60 μg h/mL). Nine patients (26%) were overexposed while 12 (34%) were underexposed. A Cmax≥10 μg/mL was seen in 20 (57%) of the patients. These percentages were equally distributed between the treatment groups both for AUC0−12 and Cmax. The equations using C0, C2 or both predict exposure, although the use of C2 seems to be more adequate in clinical practice. There were no differences in MPA exposure in patients with a repeated PK evaluated 1 wk later. Conclusion:  The use of MMF without monitoring MPA blood levels may cause over-/underexposure to the drug in stable recipients. However, in patients under MMF for more than 1 yr, MPA levels are stable and there is no need for frequent measurements.