Mycophenolic Acid Area Under The Concentration-time Curve Research Articles

Therapeutic drug monitoring of mycophenolic acid and clinical outcomes of lupus nephritis: a systematic review and meta-analysis.

Mycophenolic acid (MPA) is a primary immunosuppressive agent used in the treatment of lupus nephritis (LN). While therapeutic drug monitoring (TDM) of MPA is well established in organ transplantation, its role in LN treatment remains uncertain. Our objective was to review and summarise current knowledge on TDM of MPA in the LN treatment. A systematic search was conducted in the online databases, specifically targeted patients diagnosed with LN receiving MPA treatment. The included studies had to report both MPA pharmacokinetic parameters and renal outcomes. A random-effects model meta-analysis was conducted to assess the relationship between clinical responses and MPA pharmacokinetics. A total of 1507 studies were initially screened, resulting in the inclusion of 16 studies for meta-analysis, encompassing 433 patients. The response group exhibited significantly higher MPA area under the concentration-time curve (AUC) compared with the non-response group (51.44±21.73 mg·h/L vs 30.30±16.24 mg·h/L). The weighted mean difference (WMD) of MPA-AUC between responders and non-responders was 16.83 mg·h/L (95% CI 10.59 to 23.06; p<0.001). Similarly, trough concentration (C0) of MPA showed a strong association with renal response, evidenced by C0 values of 2.50±1.73 mg/L in the response group vs 1.51±1.33 mg/L in the non-response group (WMD 1.37 mg/L; 95% CI 0.77 to 1.97; p<0.001). There was no significant relationship identified between MPA-AUC and adverse events. This meta-analysis emphasised the meaningful correlation between MPA AUC and C0 with renal response in LN treatment. Randomised controlled trials are necessary to validate this approach and determine its superiority over fixed dosing in the context of LN treatment.

Mycophenolate Mofetil Dose Adjustment in Pediatric Kidney Transplant Recipients.

The Immunosuppressant Bayesian Dose Adjustment web site aids clinicians and pharmacologists involved in the care of transplant recipients; it proposes dose adjustments based on the estimated area under the concentration-time curve (AUCs). Three concentrations (T 20 min , T 1 h , and T 3 h ) are sufficient to estimate mycophenolic acid (MPA) AUC 0-12 h in pediatric kidney transplant recipients. This study investigates mycophenolate mofetil (MMF) doses and MPA AUC values in pediatric kidney transplant recipients, and target exposure attainment when the proposed doses were followed, through a large-scale analysis of the data set collated since the inception of the Immunosuppressant Bayesian Dose Adjustment web site. In this study, 4051 MMF dose adjustment requests, corresponding to 1051 patients aged 0-18 years, were retrospectively analyzed. AUC calculations were performed in the back office of the Immunosuppressant Bayesian Dose Adjustment using published Bayesian and population pharmacokinetic models. The first AUC request was posted >12 months posttransplantation for 41% of patients. Overall, only 50% had the first MPA AUC 0-12 h within the recommended 30-60 mg.h/L range. When the proposed dose was not followed, the proportion of patients with an AUC in the therapeutic range for MMF with cyclosporine or tacrolimus at the subsequent request was lower (40% and 45%, respectively) than when it was followed (58% and 60%, respectively): P = 0.08 and 0.006, respectively. Furthermore, 3 months posttransplantation, the dispersion of AUC values was often lower at the second visit when the proposed doses were followed, namely, P = 0.03, 0.003, and 0.07 in the 4 months-1 year, and beyond 1 year with <6-month or >6-month periods between both visits, respectively. Owing to extreme interindividual variability in MPA exposure, MMF dose adjustment is necessary; it is efficient at reducing such variability when based on MPA AUC.

Volumetric microsampling for simultaneous remote immunosuppressant and kidney function monitoring in outpatient kidney transplant recipients.

Immunosuppressant and kidney function monitoring are crucial for kidney transplant recipient follow-up. Microsamples enable remote sampling and minimise patient burden as compared to conventional venous sampling at the clinic. We developed a liquid chromatography-tandem mass spectrometry assay to quantify tacrolimus, mycophenolic acid (MPA), creatinine and iohexol in dried blood spot (DBS), and volumetric absorptive microsample (VAMS) samples. The assay was successfully validated analytically for all analytes. Clinical validation was conducted by direct comparison of paired DBS, VAMS and venous reference samples from 25 kidney transplant recipients. Patients received iohexol 5-15 minutes before immunosuppressant intake and were sampled 0, 1, 2 and 3hours thereafter, enabling tacrolimus and MPA area under the concentration-time curve (AUC) and creatinine-based and iohexol-based glomerular filtration rate (GFR) estimation. Method agreement was evaluated using Passing-Bablok regression, Bland-Altman analysis and the percentages of values within 15-30% of the reference (P15 -P30 ) with a P20 acceptance threshold of 80%. For DBS samples, method agreement was excellent for tacrolimus trough concentrations (n =25, P15 = 92.0%) and AUCs (n =25; P20 = 95.8%) and adequate for creatinine-based GFR trend monitoring (n =25; P20 = 80%). DBS-based MPA AUC assessment showed suboptimal agreement (n =16; P20 = 68.8%), but was considered acceptable given its P30 of 100%. The assay performed inadequately for DBS-based iohexol GFR determination (n =24; P20 = 75%). The VAMS technique generally showed inferior performance, but can be considered for certain situations. The assay was successfully validated for tacrolimus, MPA and creatinine quantification in DBS samples, enabling simultaneous remote kidney function trend monitoring and immunosuppressant therapeutic drug monitoring in kidney transplant recipients.

Estimation of Abbreviated Mycophenolic Acid Area Under the Concentration- Time Curve during Stable Post-transplant Period by Limited Sampling Strategy.

The Area Under the Concentration-time curve (AUC) of Mycophenolic Acid (MPA), is a valid prognosticator of the risk of rejection and the gold standard in its Therapeutic Drug Monitoring (TDM), over time post-transplantation. This study aimed to investigate MPA pharmacokinetic parameters and develop a Limited Sampling Strategy (LSS) to estimate an abbreviated MPA AUC, in the stable phase post-renal transplantation. In this study, 19 patients with normal graft function (glomerular filtration rate >70 ml/min) who fulfilled the inclusion and exclusion criteria were involved. Blood samples at various times were taken in the stable phase after transplantation. MPA plasma concentration was measured by reverse-phase high-performance liquid chromatography. MPA AUC0-12h was calculated using the linear trapezoidal rule. Multiple stepwise regression analysis was used to determine the minimal time points of MPA levels that could be used to yield model equations best fitted to MPA AUC 0-12h. The findings of this study were compared with the results of our previous study, which was done similarly in the early phase post-renal transplantation. The results demonstrated that the MPA-AUC and clearance were not affected over time, but MPA-tmax was significantly lower in the stable phase in comparison with the early phase (P=0.001). The best regression equation for AUC estimation in the stable phase was AUC=9.57*C6+27.238 (r2=0.907). The validation of the method was performed using the jackknife method. The mean prediction error of these models was not different from zero (P > 0.05) and had a high root mean square prediction error (7.91). In conclusion, the pharmacokinetics of MPA could be affected by time after transplantation, making it essential to develop a limited sampling strategy as an efficacious approach for therapeutic drug monitoring during the stable post-transplant period.

Investigation of the Association Between Total and Free Plasma and Saliva Mycophenolic Acid Concentrations Following Administration of Enteric-Coated Mycophenolate Sodium in Adult Kidney Transplant Recipients.

Mycophenolic acid (MPA) is commonly used following renal transplant. Saliva MPA concentrations may reflect the pharmacologically active form of MPA in plasma. Therapeutic drug monitoring using saliva is convenient and non-invasive. This study examined the correlation between total and free plasma and saliva MPA concentrations following enteric-coated mycophenolate sodium (EC-MS) administration in renal transplant recipients. Total and free plasma and saliva MPA concentrations were measured simultaneously in 20 adult renal transplant recipients 1-2months' post-transplant. Thirteen samples were taken pre-dose and at specified time points up until 12h post-dose. When considering all time points, correlation between total plasma and saliva MPA was r2 = 0.51 and between free plasma and saliva MPA concentrations r2 = 0.41. The correlation between total plasma MPA area under the concentration-time curve (AUC) or free plasma AUC and saliva MPA AUC was r2 = 0.25 and r2 = 0.13, respectively. The correlation between total plasma MPA AUC and total plasma MPA trough (C0) concentrations was r2 = 0.51, and between total plasma MPA AUC and saliva MPA trough concentrations, r2 = 0.03. Measurement of MPA concentration in saliva cannot currently replace plasma measurement for therapeutic drug monitoring of MPA following EC-MS administration. Additional studies are required to examine the relationship between MPA saliva concentrations and patient outcomes.

Mycophenolic acid area under the curve is associated with therapeutic response in pediatric lupus nephritis

Introduction Mycophenolic acid (MPA), the active metabolite of mycophenolate mofetil (MMF), is an effective treatment in lupus nephritis. Therapeutic drug monitoring studies of MMF suggest that area under the concentration-time curve (AUC) values of MPA of 30–45 mg.h/L may be associated with better outcome in adults with lupus but data in children is scarce. Methods In this retrospective study, 27 children were treated with MMF for biopsy proven class III–IV–V lupus nephritis between 2009 and 2016. AUC of MPA was determined on the basis of sampling times at 20, 60, and 180 minutes post-dose using a Bayesian estimator. In 25 children, AUC was performed within 6 months after kidney biopsy and MMF initiation. Treatment response at 6 months of MMF treatment was defined as follows: normal or improved GFR by 25% compared to baseline, 50% reduction of proteinuria resulting in a level Results In total, 62 AUC of MPA were analyzed [median 44 mg.h/L (IQR 33–54)] in 27 patients. The findings indicate individual dose adaptation in 32 cases (52%) to achieve an AUC target of 30–60 mg.h/L. At 6 months, 14/25 patients were defined as responders (56%) with a median AUC value of 49 [40–59] and 11/25 as non-responders (44%) with a median AUC value of 29 [24–38]. Patients with MPA AUC levels of > 45, 30–45, and 45 was significantly associated with therapeutic response (OR 3.9, 95% CI 2.4–10.5, P Conclusion Therapeutic drug monitoring leading to individualize dosing may improve the efficacy of MMF. An AUC of MPA > 45 mg.h/L is associated with a better response rate and may be considered as a target value in paediatric lupus nephritis.

Pharmacokinetics of concentration-controlled mycophenolate mofetil in proliferative lupus nephritis: an observational cohort study.

Mycophenolate mofetil (MMF) has variable pharmacokinetics. This study examines the pharmacokinetic and clinical correlations in proliferative lupus nephritis. Thirty-four patients were started on MMF, and the area under the concentration-time curve (AUC) was measured by limited sampling strategies, and dosing was adjusted to achieve an AUC of 30-60 mg·h·L. Twenty-seven patients had at least 2 measurements, and renal response was assessed within 1 year. About 61.8% of patients had mycophenolic acid (MPA) AUC <30 mg·h·L with an empiric starting dose of 30 mg/kg. About 79.4% of patients achieved renal response by 1 year, and the median time to renal response was 111 days. MMF dose per body weight had a weak correlation with the AUC and did not correlate with trough concentrations. The median dose was 1.5 g/d at entry and 2 g/d after dose modification during the induction phase. Trough concentrations had a weak correlation with AUC. Patients with serum albumin ≥35 g/L had a greater chance of having an AUC ≥30 mg·h·L. The between-patient coefficient of variability for dose-normalized AUC was 37.9% at entry and 31% within 1 year, whereas repeated measurements over time in an individual had a good intraclass correlation of 0.78. Infections occurred in 11.8% and toxicities in 5.9%. MPA exposure was not significantly associated with adverse events. Patients with an AUC ≥30 mg·h·L had greater renal response at 1 year. Lupus nephritis patients induced with concentration-controlled MMF had excellent renal response and fewer adverse events with lower than usual dosing. MPA exposure had high interpatient variability, requiring measurements for personalized dosing, and fewer adverse events. Long-term cost reduction is achievable with lower doses and good renal response in the majority of patients.

Similar MPA Exposure on Modified Release and Regular Tacrolimus

Concomitant immunosuppression may affect the mycophenolate mofetil exposure. Astellas developed a once-daily modified release formulation of tacrolimus (TacMR) with the potential to reduce the likelihood of nonadherence. It is unknown whether mycophenolic acid (MPA) area under the concentration-time curve (AUC) differs between the 2 tacrolimus (Tac) formulations. In a 2-by-2 crossover design, 20 stable renal transplant recipients on twice-daily Tac either continued their usual Tac therapy (n = 10, group 1) or switched to TacMR for a 12-week period (n = 10, group 2), after which the patients crossed over to the other formulation for another 12-week period. Pharmacokinetic profiles using limited sampling strategies were obtained before randomization (visit 1), and at 12 (visit 2) and 24 weeks (visit 3) at steady state. MPA AUC was calculated using the Pawinski formula. When analyzing visits on Tac, TacMR, and back on Tac combined, the MPA AUC for all 20 patients at baseline was 42.24 (16.98), 37.18 (13.75), and 40.09 (16.69) mg·h·L(-1), respectively, which was not statistically significant using repeated measures (P = 0.1327, R(2) = 0.1109). We conclude that MPA pharmacokinetic profiles are not altered when converting patients from Tac to TacMR.

Lower dosing of enteric-coated mycophenolate sodium (Myfortic) can achieve target mycophenolic acid exposure rapidly in most Chinese renal transplant patients: a pilot study

There are few pharmacokinetic data for enteric-coated mycophenolate sodium (EC-MPS) in Chinese kidney transplant recipients. Previously, we demonstrated that patients with 540mg EC-MPS reached target exposure on day 4 after transplantation. The aim of this study was further to confirm that mycophenolic acid (MPA) delivery with a daily total dose 1080mg EC-MPS is adequate during the early-phase posttransplantation and preliminarily assess the pharmacokinetics after a single dose and multiple doses of EC-MPS in Chinese live-donor kidney transplant recipients. Twelve patients (eight men and four women, mean age 41.3±6.78years) treated with EC-MPS, cyclosporine and corticosteroids were included in this study. Patients received a single oral dose of EC-MPS 540mg, then 540mg twice daily. MPA concentrations were measured by high-performance liquid chromatography. Twelve-hour pharmacokinetic profiles were obtained after the single oral dose and multiple doses on day 4 postoperation. The pharmacokinetic parameters were compared between a single dose and multiple doses. By using multiple stepwise regression analysis, we obtained two predictive equations of MPA systemic exposure. Bland-Altman analysis was developed to test agreement between the observed MPA area under the concentration-time curve (AUC) and the predicted MPA AUC. The mean (range) MPA AUC was 42±14.67 (29.29-75.95) mg/lh after the first dose, and 44.72±14.57 (32.06-80.79) mg/lh on day 4 after operation. MPA exposure provided by a single dose and multiple doses were similar (p>0.05). The best equations obtained were the following: 20.003+1.181C6h +7.22C8h (r=0.936) and 17.023+3.11C1h +1.245+4.988C8h (r=0.964). These equation models showed an optimal agreement between the observed MPA AUC and the predicted MPA AUC. Lower dosing of EC-MPS, compared with the standard dose (720mg twice daily), may provide enough MPA exposure for Chinese live-donor kidney transplant patients on day 4. Given that the MPA exposure by AUC correlates with the incidence of acute rejection episodes and transplant vasculopathy, the present findings may have clinical implications, and the optimum dose range of EC-MPS for patients in all ranges of body weight should also be determined.

Kidney transplant outcomes are related to tacrolimus, mycophenolic acid and prednisolone exposure in the first week

This study analysed associations between tacrolimus, mycophenolic acid (MPA) and prednisolone exposures on day 4 and month 1 post kidney transplant and clinical outcomes. Area under the concentration-time curve (AUC) for each drug was estimated using validated multiple regression-derived limited sampling strategies. Multivariate logistic regression was used to associate drug exposure with clinical outcomes. One hundred and twenty subjects were studied. Between-subject variability in dose-adjusted exposure to each medication was high. Both day 4 tacrolimus and MPA exposures were independently predictive of delayed graft function (2.6 change in odds for a standard deviation (SD) increase in tacrolimus AUC(0-12) , P = 0.02; 0.23 change in odds for a SD increase in MPA AUC(0-12) , P = 0.02). Both day 4 MPA and total prednisolone exposures were independently predictive of rejection (0.20 change in odds for a SD increase in MPA AUC(0-12) , P = 0.04; 0.40 change in odds for a SD increase in total prednisolone AUC(0-6) , P = 0.03). Lowest tertile exposure to all three immunosuppressant medications imposed significantly higher odds of rejection [adjusted odds ratio 34.2 (95% CI 4.1, 284.4), P = 0.001]. This study highlights the importance of achieving early target exposure and suggests a potential role for individualized initial dosing or early therapeutic monitoring of all three immunosuppressive agents.

Bayesian Estimation of Mycophenolate Mofetil in Lung Transplantation, Using a Population Pharmacokinetic Model Developed in Kidney and Lung Transplant Recipients

The immunosuppressive drug mycophenolate mofetil is used to prevent rejection after organ transplantation. In kidney transplant recipients, it has been demonstrated that adjustment of the mycophenolate mofetil dose on the basis of the area under the concentration-time curve (AUC) of mycophenolic acid (MPA), the active moiety of mycophenolate mofetil, improves the clinical outcome. Because of the high risks of rejections and infections in lung transplant recipients, therapeutic drug monitoring of the MPA AUC might be even more useful in these patients. The aims of this study were to characterize the pharmacokinetics of MPA in lung and kidney transplant recipients, describe the differences between the two populations and develop a Bayesian estimator of the MPA AUC in lung transplant recipients. In total, 460 MPA concentration-time profiles from 41 lung transplant recipients and 116 kidney transplant recipients were included. Nonlinear mixed-effects modelling was used to develop a population pharmacokinetic model. Patients were divided into an index dataset and a validation dataset. The pharmacokinetic model derived from the index dataset was used to develop a Bayesian estimator, which was validated using the 35 lung transplant recipients' profiles from the validation dataset. MPA pharmacokinetics were described using a two-compartment model with lag time, first-order absorption and first-order elimination. The influence of ciclosporin co-treatment and the changes over time post-transplantation were included in the model. Lung transplant recipients had, on average, a 53% slower absorption rate and 50% faster MPA apparent oral clearance than kidney transplant recipients (p < 0.001). In lung transplant recipients, the bioavailability was, on average, 31% lower in patients with cystic fibrosis than in patients without cystic fibrosis (p < 0.001). The Bayesian estimator developed using the population pharmacokinetic model--and taking into account ciclosporin co-treatment, cystic fibrosis and time post-transplantation, with concentrations measured at 0, 1 and 4 hours after mycophenolate mofetil dose administration--resulted in a non-significant bias and mean imprecision of 5.8 mg · h/L. This higher imprecision compared with those of similar estimators that have previously been developed in kidney transplantation might have been caused by the high MPA pharmacokinetic variability seen in the lung transplant recipients and by the fact that a large proportion of the patients did not receive ciclosporin, which reduces variability in the elimination phase of MPA by blocking its enterohepatic cycling. Lung transplant recipients have a slower MPA absorption rate and faster apparent oral clearance than kidney transplant recipients, while cystic fibrosis results in lower MPA bioavailability. A Bayesian estimator using MPA concentration-time samples at 0, 1 and 4 hours post-dose had the best predictive performance.

Mycophenolic Acid Exposure in High- and Low-Weight Renal Transplant Patients After Dosing With Mycophenolate Mofetil in the Opticept Trial

The Opticept trial was an open-label, randomized, multicenter trial involving 720 kidney recipients. Three immunosuppressant dosing regimens were evaluated, including both fixed and concentration-controlled dosing of mycophenolate mofetil in combination with standard and reduced calcineurin inhibitor levels. Mycophenolic acid (MPA) levels were measured, yielding one of the largest databases to assess the impact of variables on MPA exposure. The present subset analysis evaluated the effect of baseline body weight in three noncontiguous weight categories on MPA exposure at steady state (Day 90) in patients receiving tacrolimus. Multivariate linear regression models assessed the relationship between area under the concentration-time curve (AUC) and several variables. In all, 219 patients had baseline weights in the three categories and an MPA AUC at Day 90: 50 kg or less (n = 12, all female); 60 to 80 kg (n = 136); or 100 kg or greater (n = 71). In overall comparisons by weight class, clearance increased with increased weight, resulting in an inverse relationship between dose-corrected MPA AUCs and weight at Day 90 (P < 0.0001). In patients of extreme weight, wide disparities of MPA exposure were measured despite the mean mycophenolate mofetil dose, notably in those 50 kg or less who had comparatively high dose-corrected MPA AUCs. Patients at the extremes of weight might be at risk of over- or underimmunosuppression unless doses are adjusted.

Therapeutic Monitoring of Mycophenolate in Transplantation: Is It Justified?

Mycophenolate mofetil (MMF) is the preferred antimetabolite in solid organ transplantation. It is a prodrug that undergoes pre-systemic metabolism to mycophenolic acid (MPA), the active drug moiety. MMF is typically administered as a fixed dose without routine monitoring of MPA concentrations. However, a role for therapeutic drug monitoring (TDM) of MPA has been suggested based on the drug's narrow therapeutic window and considerable between-subject variability. Dose-normalized MPA area under the concentration-time curve (AUC) has been observed to vary >/=10-fold. Some of this variability may be accounted for by patient variability in renal and liver function, serum albumin and haemoglobin levels, body mass, concomitant medication exposure and genetic polymorphisms in enzymes responsible for drug metabolism and transport, but much is unexplained. Widespread adoption of MPA TDM has been limited by the impracticality of full 0 to 12 hour AUC measurement (AUC(0-12)), poor correlation between pre-dose MPA concentration and AUC(0-12), ongoing questions regarding the utility of free versus total MPA measurements and lack of evidence correlating MPA exposure with clinical outcomes. Two recent randomized studies evaluating the role of MPA TDM in renal transplant recipients have reported conflicting results. Promising areas of ongoing study include use of Bayesian forecasting to predict MPA dosage and measurement of inosine monophosphate dehydrogenase activity. This review provides an overview of the pharmacokinetics of MMF in solid organ transplantation, and discusses the benefits and limitations of MPA monitoring. Areas that require additional research are identified.

Evaluation of the Practicability of Limited Sampling Strategies for the Estimation of Mycophenolic Acid Exposure in Chinese Adult Renal Recipients

The immunosuppressive potential of mycophenolic acid (MPA) correlates well with MPA exposure [area under the concentration-time curve (AUC)]. Monitoring MPA AUC is important and helpful for maintaining the efficacy of mycophenolate mofetil while minimizing its side effects, but full MPA AUC monitoring is laborious, cost prohibitive, and impractical. Limited sampling strategies have been proposed as an alternative method for estimating MPA exposure. The objective of this study was to evaluate the practicability of different limited sampling strategies for the estimation of MPA exposure. A total of 56 pharmacokinetic profiles from 53 adult renal recipients were used to evaluate the practicability of 10 published models. Standard correlation and linear regression analysis were used to compare the estimated MPA AUCs and corresponding full MPA AUCs, and the percentage of profiles for which prediction error fell within +/-20% was also used to assess the practicability of these models. Agreement between the estimated MPA AUCs and full MPA AUCs was further tested by Bland and Altman analysis. The model, based on four sampling time points, used the formula AUC = 12.61 + 0.37 x C0.5 + 0.49 x C1 + 3.22 x C4 + 8.17 x C10, was superior to all other evaluated models, with the highest coefficient of determination (r = 0.88), a low percentage prediction error (2.79%), and good agreement according to Bland and Altman analysis. Prediction errors of 87.5% (49/56) of profiles were within 20%, which was the highest of all the models. This algorithm can be reliably used for estimating MPA exposure in adult renal transplant patients treated with cyclosporine as concomitant immunosuppressant. Another model based on the formula AUC = 8.22 + 3.16 x C0 + 0.99 x C1 + 1.33 x C2 + 4.18 x C4 also has acceptable predictive performance, and it may also be practical, especially in outpatient settings, in view of its distribution of time points.

Cyclosporine interacts with mycophenolic acid by inhibiting the multidrug resistance-associated protein 2.

In mycophenolate mofetil (MMF)-treated organ transplant recipients, lower mycophenolic acid (MPA) plasma concentrations have been found in cyclosporine (CsA) compared with tacrolimus (Tac)-based immunosuppressive regimens. We previously demonstrated that CsA decreases exposure to MPA and increases exposure to its metabolite MPA-glucuronide (MPAG), possibly by interfering with the biliary excretion of MPAG. To elucidate the role of the multidrug resistance-associated protein (Mrp)-2 in the interaction between MMF and CsA, we treated three groups of 10 Mrp2-deficient rats (TR- rat) for 6 days with either vehicle, CsA (8 mg/kg) or Tac (4 mg/kg) by oral gavage. Hereafter, co-administration with MMF (20 mg/kg) was started in all groups and continued through day 14. The 24-h MPA/MPAG area under the concentration-time curve (AUC) was determined after single (day 7) and multiple MMF doses (day 14). On both study days, there were no significant differences in the mean MPA and MPAG AUC between CsA and Tac-treated animals. We conclude that the pharmacokinetics of MMF are comparable in Mrp2-deficient rats receiving either CsA or Tac as co-medication. This finding suggests that CsA-mediated inhibition of the biliary excretion of MPAG by the Mrp2 transporter is the mechanism responsible for the interaction between CsA and MMF.

A retrospective analysis of mycophenolic acid and cyclosporin concentrations with acute rejection in renal transplant recipients

Objectives: Although monitoring of cyclosporin (CsA) is standard clinical practice postrenal transplantation, mycophenolic acid (MPA) concentrations are not routinely measured. There is evidence that a relationship exists between MPA area under the concentration-time curve (AUC) and rejection. In this study, a retrospective analysis was undertaken of 27 adult renal transplant recipients. Methods: Patients received CsA and MPA therapy and had a four-point MPA AUC investigation. The relationship between MPA AUC performed in the first week after transplantation, as well as median trough cyclosporin concentrations, and clinical outcomes in the first month posttransplant were evaluated. Results: A total of 12 patients experienced biopsy proven rejection (44.4%) and 4 patients had gastrointestinal adverse events (14.8%). A statistically significant relationship was observed between the incidence of biopsy proven rejection and both MPA AUC ( p = 0.02) and median trough CsA concentration ( p = 0.008). No relationship between trough MPA concentration and rejection was observed ( p = 0.21). Only 3 of 11 (27%) patients with an MPA AUC > 30 mg.h/L and a median trough CsA > 175 μg/L experienced acute rejection, compared with a 56% incidence of rejection for the remaining 16 patients. Patients who experienced adverse gastrointestinal events had significantly lower MPA AUC ( p = 0.04), but median trough CsA concentrations were not significantly different ( p = 0.24). Further, 3 of these 4 patients had rejection episodes. Conclusions: In addition to standard CsA monitoring, we propose further investigation of the use of a 4-point sampling strategy to predict MPA AUC in the first week posttransplant, which may facilitate optimization of mycophenolate mofetil dose at a time when patients are most vulnerable to acute rejection.

Mycophenolic acid concentrations are associated with cardiac allograft rejection

Background: Mycophenolate mofetil (MMF) therapy decreases the incidence of allograft rejection following solid-organ transplantation. Current dosing strategies of MMF are not routinely adjusted based on mycophenolic acid (MPA) area under the concentration-time curve (AUC), MPA trough, or free MPA (fMPA) AUC values. Methods To determine the clinical significance of MPA concentrations following orthotopic heart transplantation (OHT), we measured pre-dose MPA trough, MPA free fraction, an estimated MPA AUC using an abbreviated sampling schedule, and fMPA AUC in 38 consecutive patients. We measured MPA concentrations using a validated high-performance liquid chromatography method and graded endomyocardial biopsies based on the International Society for Heart and Lung Transplantation (ISHLT) grading system. Results The MPA values for the study group were as follows: MPA trough of 1.2 ± 0.6 μg/ml; MPA free fraction of 1.9 ± 0.4%; MPA AUC of 44.5 ± 16.1 μg/hour/ml; and fMPA AUC of 0.83 ± 0.30 μg/hour/ml. We compared patients with Grade 0 ( n = 22), Grade 1 ( n = 13), or Grade 2/3 ( n = 3). The MPA AUC values were lower in patients with Grade 2/3 than in patients with Grade 0 (26.1 ± 6.6 vs 42.8 ± 14.0 μg/hour/ml, p < 0.08) or Grade 1 rejection (26.1 ± 6.6 vs 51.7 ± 17.5 μg/hour/ml, p < 0.05). The fMPA AUC values were lower in patients with Grade 2/3 than with patients with Grade 0 (0.49 ± 0.11 vs 0.81 ± 0.25 μg/hour/ml, p < 0.05) or Grade 1 (0.49 ± 0.25 vs 0.95 ± 0.34 μg/hour/ml, p < 0.05) rejection. We noted a trend in MPA trough concentrations between patients with Grade 2/3 vs 0 (0.65 ± 0.15 vs 1.20 ± 0.58 μg/ml, p = 0.15) and Grade 1 (0.65 ± 0.15 vs 1.24 ± 0.72 μg/ml, p = 0.14) rejection. Conclusion These preliminary results suggest that lower MPA AUC and fMPA AUC values are associated with cardiac allograft rejection in heart transplant recipients. Individualizing MMF dosing based on MPA determinations may minimize the risk of rejection following OHT.