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 microg h/mL). Nine patients (26%) were overexposed while 12 (34%) were underexposed. A Cmax> or =10 microg/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.

Bioequivalence of a new cyclosporine a formulation to Neoral.

New cyclosporine A (CsA) formulations must prove their bioequivalence to Neoral, the reference CsA formulation, to allow free prescription for the patients. The aim of this study was to compare the pharmacokinetics (PK) of a new CsA formulation (Zinograf-ME), produced by Strides-Arcolab, to Neoral and to demonstrate their interchangeability in stable renal transplant recipients. Twelve-hour PK studies were obtained from 18 (13 M/5 F) adult patients (mean age 44.7 +/- 12 years). They received their renal allografts from 13 cadaver and 5 living donors. Before enrollment, all patients were receiving a third generic CsA for a mean of 48 months. Nine patients were also under azathioprine and 9 under mycophenolate mofetil; 17 received prednisone. A single oral dose of either Zinograf or Neoral was administered. The first PK study was performed with one formulation, and 1 week later, a second PK was done with the other formulation. During the washout period, patients continued taking the third CsA formulation. The drug substitution was done milligram-for-milligram. The CsA whole-blood level was measured by TDx immunoassay. Mean +/- SD of area under the curve (AUC), maximum concentration (C(max)), and concentration at the second hour (C2) of Zinograf were not statistically different from those with Neoral (4019 +/- 1466 vs 3971 +/- 1325 ng x h/mL, 998 +/- 376 vs 1021 +/- 356 ng/mL, and 707 +/- 254 vs 734 +/- 229 ng/mL, respectively). In the same way, the Zinograf 90% confidence interval for either C(max) (-123, +77 ng/mL) or AUC (-214, +311 ng.mL/h) were within the Neoral bioequivalence interval for the same parameters (+/-204 ng/mL and +/-794 ng x mL/h, respectively). These data demonstrate that the ZinografME CsA formulation is bioequivalent to Neoral.

Mycophenolic acid pharmacokinetics in stable pediatric renal transplantation.

Mycophenolate mofetil (MMF) is given to children in fixed doses based either on body weight or body surface area. There are data indicating mycophenolic acid (MPA) blood levels should be monitored in the early period of transplantation. However, there is little information regarding MPA pharmacokinetics (PK) in stable pediatric recipients. We evaluated MPA-PK in 20 stable renal transplant children (11.7+/-1.9 years) under long-term (46+/-31 months) MMF (26.1+/-7 mg/kg per day or 785+/-183 mg/m(2) per day) therapy plus prednisone and cyclosporin A (n=16), tacrolimus (n=3), or MMF/prednisone (n=1). Total MPA levels were measured using the EMIT-MPA assay at 0, 1, 2, 3, 4, 6, and 8 h after an oral dose of MMF. The level at 12 h was considered equal to the trough level for AUC(0-12) calculation. Mean C(0), C(max), AUC (0-12), and T(max )were 3.46+/-1.32, 13.5+/-0.58 microg/ml, 63.2+/-24.4 microg x h/ml, and 1.3+/-0.6 h, respectively. Six (30%) children were considered to have an adequate exposure (36-54 microg x h/ml) to MPA, 11 (55%) showed an AUC(0-12 )>54 microg.h/ml, and 3 (15%) showed an AUC(0-12 )<36 microg x h/ml. A C(max )>/=10 microg/ml was seen in 13 (65%) children. MMF dose did not correlate with AUC(0-12) or C(max). The combination of variables C(0), C(1), and C(4 )provided an equation to predict exposure (r(2)=0.75) where AUC(0-12)=12.62+(7.78 x C(0))+(0.90 x C(1))+(1.30 x C(2)) (P<0.001). The use of MMF without monitoring MPA blood levels may cause unnecessary overexposure to the drug in stable pediatric recipients.