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Mycophenolic acid pharmacokinetics in stable pediatric renal transplantation
Elias David-Neto1, Lilian Monteiro Pereira Araujo, Nairo Massakazu Sumita
1Renal Transplant Unit, Division of Urology and Nephrology, Hospital das Clínicas da Faculdade de Medicina, University of São Paulo, São Paulo, Brazil. elias.david.neto@attglobal.net
Abstract:
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.
Insights
Monitoring mycophenolic acid (MPA) blood levels in stable pediatric renal transplant patients on mycophenolate mofetil (MMF) therapy is crucial. Many children experience suboptimal or excessive drug exposure, highlighting the need for personalized dosing strategies.
Area of Science:
- Pharmacology
- Pediatric Nephrology
- Transplantation Medicine
Background:
- Mycophenolate mofetil (MMF) is commonly prescribed for pediatric renal transplant recipients.
- Current dosing relies on weight or body surface area, with limited data on pharmacokinetics in stable pediatric patients.
- Monitoring mycophenolic acid (MPA) levels is recommended early post-transplant, but less is known about stable long-term recipients.
Purpose of the Study:
- To evaluate the pharmacokinetics (PK) of MPA in stable pediatric renal transplant recipients.
- To assess MPA exposure levels and identify factors influencing them.
- To determine if fixed-dose MMF therapy leads to adequate MPA exposure in this population.
Main Methods:
- Prospective evaluation of MPA pharmacokinetics in 20 stable pediatric renal transplant patients.
- Patients received long-term MMF therapy with standard immunosuppressants.
- Total MPA levels were measured at multiple time points (0, 1, 2, 3, 4, 6, 8, 12 h) post-dose using the EMIT-MPA assay.
Main Results:
- Mean MPA AUC(0-12) was 63.2 μg*h/mL, with significant variability.
- Only 30% of patients had adequate MPA exposure (36-54 μg*h/mL); 55% were overexposed (>54 μg*h/mL), and 15% were underexposed (<36 μg*h/mL).
- MMF dose did not correlate with MPA exposure; a predictive equation using early concentration measurements (C(0), C(1), C(4)) was developed (r²=0.75).
Conclusions:
- Fixed-dose MMF therapy in stable pediatric renal transplant recipients often results in suboptimal or excessive MPA exposure.
- Routine monitoring of MPA blood levels is essential to optimize dosing and prevent adverse events.
- A predictive model using early MPA concentrations may aid in individualizing MMF therapy.