Mycophenolic Acid Trough Research Articles

Comparison of mycophenolic acid pharmacokinetic parameters in kidney transplant patients within the first 3 months post-transplant

The aim of this study was to investigate the effect of time on pharmacokinetic (PK) parameters of mycophenolic acid (MPA) in the early post-transplant period in kidney recipients. MPA is the active metabolite of mycophenolate mofetil (MMF), which was introduced into clinical practice ten years ago. Mycophenolate mofetil was co-administered with cyclosporin (CsA) in a subgroup of 23 patients and with tacrolimus (Tac) in a subgroup of 10 patients. MPA plasma concentration profiles were measured by a validated high performance liquid chromatography method 1 week, 2 and 3 months after transplantation. Despite a comparable MMF dose, a large inter-patient variability in both MPA area under the curve (AUC) from 0 to 12 h (range 10.03-135.4 microg h/mL) and in predose concentrations (0.31-6.09 microg/mL) was observed. Patients with AUC > 35 microg h/mL showed better (P < 0.1) renal function than patients with AUC < 20 microg h/mL (mean creatinine concentration 1.48 +/- 0.12 vs. 3.35 +/- 0.4 mg/dL respectively). The total MPA trough and AUC did not correlate with biochemical parameters: leucocyte cell count and haematocrit. A higher trough level of the metabolite MPA glucuronide (MPAG) in the 1 week after transplantation was found when compared with the 3-month level (mean 150.1 +/- 146.7; range 17.1 to 560 vs. 75.8 +/- 40.0; range 27.3 to 174.2 microg/mL). The concentration of MPA, and MPA AUC values were significantly lower in patients receiving MMF and CsA than those receiving MMF and Tac during all three periods studied (P < 0.02). The influence of C(0) and MPA AUC values on the risk of graft rejection was investigated using receiver operating characteristic (ROC) curve analysis. The area under the ROC curve for AUC was 0.847, whereas that of C(0) was 0.632. The MPA AUC(0-12h) appeared to be the more effective PK parameter for predicting acute rejection. We recommend that routine MPA and MPAG therapeutic drug level monitoring should be an important part of MMF therapy.

Inosine monophosphate dehydrogenase activity in renal allograft recipients during mycophenolate treatment

Objective. Mycophenolic acid (MPA) exerts its immunosuppression by inhibiting inosine 5′‐monophosphate dehydrogenase (IMPDH), depleting activated lymphocytes of guanine nucleotides and retarding their proliferation. An optimal strategy for monitoring has not been established for mycophenolate mofetil (MMF) in renal transplantation, and clinical investigations of the pharmacokinetic‐pharmacodynamic relationship are warranted. Material and methods. Mycophenolic acid pharmacokinetics and whole blood cell IMPDH activity were investigated in two separate groups of renal allograft recipients. One group was studied within the 12‐h dose interval, while the second group was examined by pre‐dose samples pre‐transplant and then repeatedly during 8 weeks post‐transplant. Results. An inverse relationship between plasma MPA and IMPDH activity within the dose interval was demonstrated. Minimum IMPDH activity was a median 8 % of values pre‐MMF dose, coinciding with the MPA peak. Six hours post‐dose, IMPDH activity had returned to pre‐dose values. Patients receiving MMF had a 4.5‐fold higher pre‐dose enzyme activity than transplanted patients without MMF. During the 8 weeks post‐transplant, the median MPA trough concentration was fairly stable. Following an initial decrease during the first 4 days post‐transplant, IMPDH activity gradually increased during the 40 days post‐transplant, reaching 5‐fold the pre‐transplant values. Conclusions. Provided that the changes in IMPDH activity in whole blood cells predict the clinical effect, these pharmacokinetic‐pharmacodynamic findings may prove useful in the attempts to identify optimal timing and range for the monitoring of mycophenolate in renal transplantation. The question of whether MPA concentrations or measurements of IMPDH activity per se will be the optimal way of monitoring this immunosuppressant remains open and will only be answered by prospective clinical testing.

Mycophenolic Acid 12-h Trough Level Monitoring in Renal Transplantation: Association with Acute Rejection and Toxicity

Studies of renal transplantation utilizing trough plasma level monitoring of mycophenolic acid (MPA) have shown inconsistent associations with toxicity and rejection. In this study, 5600 12-h trough MPA samples from 121 renal transplant recipients immunosuppressed with mycophenolate mofetil (MMF) and tacrolimus in a steroid sparing protocol (steroids for 7 days only) were sequentially analyzed. Higher MPA levels were associated with lower hemoglobin concentrations and anemia (hemoglobin <10 g/dL). Similarly, higher MPA levels were associated with lower total white cell counts and an increased incidence of leucopenia (total white cell count <4.0 x 10(9)/L). Hypoalbuminemia and renal impairment were also associated with hemotoxicity. MMF-associated diarrhea and viral infection were associated with higher MPA levels. Conversely, biopsy-proven acute rejection within the first month post-transplantation was associated with lower MPA levels. Anti-CD25 antibody induction was also associated with reduced rejection rates. No association was seen between MPA levels and platelet count, thrombocytopenia or bacterial infection. An MPA level of 1.60 mg/L early post-transplantation best discriminated patients with and without rejection, and an MPA level of 2.75 mg/L best discriminated patients with and without toxicity later post-transplantation.

Influence of Co‐Medication with Sirolimus or Cyclosporine on Mycophenolic Acid Pharmacokinetics in Kidney Transplantation

The pharmacokinetics of mycophenolic acid (MPA)--the active metabolite of mycophenolate mofetil (MMF)--is significantly influenced by co-medications. The impact of sirolimus on daily MPA exposure, however, has not been investigated so far. As a part of the study aimed at investigating the efficacy of Campath-1H induction therapy in a steroid-free regimen in kidney transplantation, MPA plasma levels were serially measured in 21 patients treated with low-dose sirolimus (SRL) or low-dose CsA both in addition to low-dose MMF over 12 months post-operatively. Full pharmacokinetic profiles were compared at month 6 and 12 post-surgery. Mean dose-adjusted MPA trough levels were 4.4-fold higher in patients on combined SRL and MMF than in those given CsA and MMF. Pharmacokinetic studies demonstrated that mean MPA C(max) and T(max) were comparable in the two groups, while mean MPA AUC(0-12) was higher in SRL than CsA treated patients. The pharmacokinetic profile of SRL- but not of CsA-group showed a second peak consistent with the enterohepatic recirculation of MPA. These findings suggest that SRL and CsA have different effects on MPA metabolism and/or excretion eventually affecting its immunosuppressive property and/or toxicity. CsA, but not SRL, inhibits MPA enterohepatic recirculation, reducing MPA daily exposure.

Mycophenolic acid clinical pharmacokinetics influenced by a cyclosporine C2 based immunosuppressive regimen in renal allograft recipients

Therapeutic drug monitoring of mycophenolic acid (MPA) in combination with cyclosporine 2-h concentration (CsA C2, n = 68) or tacrolimus trough concentration (n = 10) was investigated by repeated measurements of MPA and MPA-glucuronide (MPAG) trough concentrations in renal allograft recipients during the first 3 months post-transplant. The acute rejection rate was lower (19% vs. 43%; P < 0.05) in patients achieving CsA C2 target range during the first week (1600-2000 microg/l), n = 26, compared with those who did not, n = 42. Median MPA concentration was 0.9 and 1.2 microg/ml in patients within or below C2 range, respectively (P = 0.19). CsA C2 correlated with MPAG-to-MPA ratio (P < 0.01, r = 0.91) and gamma-glutamyl-transpeptidase (GGT, P < 0.01, r = 0.86). Total MPA concentration increased during the 3 months, but not in patients on tacrolimus. High CsA C2 lowered the acute rejection rate and plasma MPA. High CsA C2 is associated with elevated GGT, probably because of cholestatic effects, which explain the increased MPAG-to-MPA ratio. Increasing MPA concentration is ascribed to per-protocol CsA C2 reductions. In conclusion, CsA may confound the relationship between MPA and the incidence of rejection, and contribute to the difficulty of obtaining a therapeutic range for MPA in clinical practice.

Relationship of mycophenolic acid exposure to clinical outcome after hematopoietic cell transplantation

Mycophenolate mofetil is used increasingly to provide immunosuppression after nonmyeloablative allogeneic hematopoietic cell transplantation. There is wide variability in the pharmacokinetics of mycophenolic acid (MPA), the active metabolite, and low concentrations are associated with rejection after organ transplantation. We hypothesized that low MPA was associated with poorer engraftment and a higher incidence of acute graft versus host disease. We evaluated the pharmacokinetics in 87 adult subjects undergoing nonmyeloablative-related and nonmyeloablative-unrelated hematopoietic cell transplantation who were receiving 1 g mycophenolate mofetil orally or intravenously every 12 hours plus cyclosporine (INN, ciclosporin). Subjects with an unbound MPA area under the curve (AUC) from 0 to 6 hours of less than 150 ng . h/mL had a higher cumulative incidence of grade II-IV acute graft versus host disease than subjects with a greater AUC (68% versus 40%, P = .02). An unbound AUC from 0 to 12 hours of less than 300 ng . h/mL was also associated with more frequent acute graft versus host disease (58% versus 35%, P = .05). There was no association between graft versus host disease and trough concentrations (P < or = .62). A higher cumulative incidence of engraftment was associated with total MPA trough concentrations greater than 1 microg/mL (P < .01). All engraftment failures occurred in the cord blood recipients. About one half of subjects were below the unbound AUC target after oral dosing with nearly a 5-fold variability in AUC. Intravenous dosing achieved unbound targets better than oral dosing. The current practice of dosing with 1 g twice daily provides inadequate plasma concentrations in many patients, and doses of at least 3 g/d are likely necessary. Therapeutic monitoring of MPA concentrations with dose adjustment into the therapeutic target appears to be necessary for the most effective use of mycophenolate mofetil.

Trough levels of mycophenolic acid and its glucuronidated metabolite in renal transplant recipients

The prophylactic use of the immunosuppressant prodrug, mycophenolate mofetil (MMF) to prevent graft rejection in renal transplant patients is continuing to increase. We measured trough levels of the active metabolite, mycophenolic acid (MPA) and its inactive glucuronide (MPAG) in renal recipients with the aim of characterizing individual variability and of ascertaining factors influencing trough levels, in particular the effect of differences in renal function and the effect of drugs given concurrently. Laboratory and clinical data obtained in 35 renal recipients treated with triple therapy (MMF, cyclosporin A (CsA), steroids) were included in this retrospective study. Trough levels of MPA and MPAG were obtained after transplantation and up to 16 months post transplantation where the mean observation period was 5.7 months. Plasma levels were measured using a validated HPLC assay. A total of 212 plasma concentrations of MPA and 209 of MPAG were measured. There was considerable intra- and interindividual variability in MPA and MPAG trough levels especially in the early post-transplantation phase. At a fixed dose of 2 g/d MMF, the mean MPA level during the first 30 days averaged 1.46 +/- 1.31 microg/ml vs. 1.87 +/- 0.89 microg/ml after 30 days and later (p = 0.130) and the mean MPAG concentration averaged 188.1 = 142.8 [microg/ml vs. 98.09 +/- 52.4 microlg/ml (p 0.003). The MPAG levels were positively correlated with the serum creatinine concentrations (r = 0.815, p < 0.001), and in the case of MPA there was a correlation with the serum protein concentrations (r = 0.258, p = 0.001). Concomitant drug treatment using CsA, steroids and furosemide were without effect of the measured plasma concentrations, but in the case of xipamide (+) and diltiazem (-) an effect on MPA and MPAG levels and a co-effect depending on the serum creatinine could not be excluded. Neither CsA trough levels nor hemoglobin levels were related to MPA and MPAG trough levels. The data of this study demonstrate that there is substantial individual variability in the trough levels of MPA and MPAG after renal transplantation which may be associated with the functional status of the graft and the serum protein level. Whether comedication with xipamide and diltiazem affects the plasma levels of MPA and MPAG remains to be clarified in further investigations.

Mycophenolate Mofetil in Islet Cell Transplant: Variable Pharmacokinetics but Good Correlation Between Total and Unbound Concentrations

The authors investigated the pharmacokinetics of mycophenolic acid over 1 year in 8 Caucasian women undergoing islet cell transplantation. Total mycophenolic acid AUC(0-12) mcg x h/mL before day 60 was 62.1-67.8, declining to 33.6-64.7 thereafter (P = .61). Median total trough concentrations were 1.16-2.90 mcg/mL. Unbound AUC(0-12) was 412-673 ng x h/mL and did not change over time (P = .30). Median percent unbound mycophenolic acid was 0.95% of total concentrations. Individual unbound and total mycophenolic acid concentrations were highly correlated (r2 = 0.94). Total mycophenolic acid trough concentration and total AUC(0-12) were modestly correlated (r2 = 0.65). Intra- and interpatient variability of systemic mycophenolic acid exposure was high. Six patients required dose reductions prior to day 60 due to adverse effects. All subjects achieved insulin independence; 3 later lost graft function. The trend toward higher exposure in the early periods followed by dose reductions suggests that lower initial doses and therapeutic drug monitoring may be necessary.

Determinants of Mycophenolic Acid Levels After Renal Transplantation

There are data suggesting an association between mycophenolic acid (MPA) levels and acute rejection and toxicity in renal transplant recipients treated with mycophenolate mofetil (MMF), and therefore, knowledge of factors determining MPA levels may aid in accurate adjustment of MMF dosage. A total of 4970 samples taken 12 hours postdose were analyzed for MPA by immunoassay at regular intervals from the first week posttransplantation in 117 renal transplant patients immunosuppressed with MMF and tacrolimus in a steroid-sparing regimen (prednisolone for the first 7 days only). MPA levels rose in the first 3 months and stabilized thereafter; dose-normalized MPA levels rose throughout the first 12 months and subsequently stabilized. Multivariate analysis by means of a population-averaged linear regression showed positive associations between MPA level and total daily dose (P < 0.001) but not individual dose or total daily dose corrected for body weight. Positive associations were also seen with serum albumin (P = 0.01), tacrolimus trough level (P = 0.01), and female gender (P = 0.002). The association with tacrolimus levels diminished with time. Negative associations were seen between MPA level and higher estimated creatinine clearance (P < 0.001), and also with increasing alanine transaminase levels (P = 0.002), the use of oral antibiotics (P < 0.001), and infective diarrhea (P < 0.001). The latter findings may be related to changes in enterohepatic recirculation of MPA. Many clinical variables show associations with trough MPA levels. An understanding of these factors may aid therapeutic monitoring of MMF.

Long-term follow-up of pediatric transplant recipients: mycophenolic acid trough levels are not a good indicator for long-term graft function.

Mycophenolate mofetil (MMF) has the potential of decreasing acute rejection episodes early following renal transplantation. Pharmocokinetic monitoring of mycophenolic acid (MPA) trough levels is performed by many centers. MMF has also proved successful in improving long-term graft function in patients with chronic allograft nephropathy (CAN). However, no data for long-term monitoring of MPA in children have yet been published. MMF therapy with a dose of 600 mg/m2 twice daily was initiated in 42 children (median age 9.4 yr, range 1.4-15.1) after a median period of 3.8 yr (range 1.0-10.6) post-transplantation-- according to significant increases in serum creatinine. CAN was diagnosed by renal biopsy and the amount of fibrosis was quantified with PicroSiriusRed staining. MMF therapy was combined with ciclosporin A and prednisolone. MPA-C0-levels, measured by high-pressure liquid chromatography, were tested every 3 months. In 12 children a full MPA area under the curve concentration (AUC) was measured. The glomerular filtration rate (GFR) was calculated at the start of MMF therapy and 2 yr later. After initiation of MMF, the calculated GFR did not decrease further in 22 children and mean GFR remained stable for 2 yr in the whole study group. There was a significant correlation between MPA levels 75 min after administration and the full AUC (r = 0.94, p < 0.001) but no correlation between trough levels and AUC (r = -0.07, p > 0.05). The mean MPA trough level was 2.8 +/- 1.3 ng/mL. The intra-individual coefficient of variation was 2.6 +/- 1.4. There was no correlation between mean MPA trough levels and GFR development after 2 yr (r = 0.03, p > 0.05). In children with an MPA level below 1.2 mg/L (n = 5), the mean GFR decline was no different to those with a higher level (p > 0.05). Drug monitoring of MPA trough levels had no impact on long-term graft function in kidney recipients. MPA levels taken 75 min after administration showed a high correlation with MPA-AUC whereas C0-levels did not correlate. The value of C75 drug measurements for monitoring renal allograft survival will have to be judged in future studies.

Lack of Correlation Between MMF Dose and MPA Level in Pediatric and Young Adult Cardiac Transplant Patients: Does the MPA Level Matter?

To determine the correlation between mycophenolate mofetil (MMF) dose and mycophenolic acid (MPA) level as well as its impact on rejection among young cardiac transplant recipients (OHT), trough concentrations of MPA and its metabolite, mycophenolic acid glucuronide (MPAG), were measured following MMF doses of 1200 mg/m2/d (max 3000 mg/d). Corresponding endomyocardial biopsy (EMB) grades and calcineurin inhibitor levels were recorded with simultaneous MPA/MPAG levels. Correlation coefficients were derived between MMF dose and MPA/MPAG levels. Contingency analysis evaluated the relation between MPA level and EMB score.Twenty-six patients (median age 15.4 years) had 120 MPA/MPAG levels measured. Average MMF dose was 1208.8 mg/m2/d with median MPA and MPAG concentrations: 2.1 (therapeutic: 1.0–3.5 μg/mL) and 48 μg/mL (reference range: 35–100 μg/mL), respectively. Only 50% of patients consistently achieved therapeutic levels with standard dosing. No correlation was found between MMF dose and MPA/MPAG levels. In the presence of therapeutic calcineurin inhibition, EMB grade ≥ 2 occurred more with MPA concentrations <2.5 μg/mL (p = 0.01).In young OHT patients, MMF dose does not correlate with MPA/MPAG levels, and standard MMF dosing fails to consistently achieve ‘therapeutic’ MPA concentrations. An MPA trough level <2.5 μg/mL was more frequently associated with EMB grade ≥ 2. Concentration rather than dose-driven management is a more prudent strategy when using MMF.

STANDARD DOSE ENTERIC COATED MYCOPHENOLATE SODIUM (E-MPS) DELIVER RAPID THERAPEUTIC MPA EXPOSURE IN KIDNEY TRANSPLANT RECIPIENTS.

P738 Aims: Previous studies showed that prescription of mycophenolate mofetil and E-MPS can deliver adequate therapeutic exposure of mycophenolic acid (MPA) in only 15 % and 55 % of kidney transplant recipients at two weeks post transplantation (target AUC0-12h of MPA = 30-60 ug.h/ml). However, it is unknown whether this information can be extrapolated to patients with all range of body weight. For therapeutic purpose, it is considered important to reach MPA exposure target as soon as possible. To further clarify the success rate of adequate MPA delivery at the early post kidney transplant period, we studied the pharmacokinetics of MPA from patients who were prescribed standard dose of E-MPS (MyforticR). Methods: Pharmacokinetic studies of E-MPS was done after the first dose of 720 mg E-MPS. This was given within 24-48 hour after operation. Blood were drawn at 0, 0.5, 1, 2, 3, 4, 8 and 12 hours for measurement of MPA and MPA glucoronide (MPAG) in plasma after E-MPS administration. MPA and MPAG concentrations were measured by high performance liquid chromatography. The pharmacokinetics of MPA and MPAG were analyzed based on model-independent approach. The AUC 0-12h of MPA and MPAG were calculated using trapezoidal rule. Later on, 720 mg bid of E-MPS was prescribed daily. The pharmacokinetic investigation of MPA and MPAG was repeated at 2 weeks post transplantation. Concomitant immunosuppression included cyclosporin and prednisolone. Demographic datas were expressed as mean ± SD. The clinical outcomes were examined and correlated. Results: A total of 12 kidney transplant recipients were studied. Mean ± SD values for age, HLA mismatch and body weight were 39 ± 9 years, 2.6 ± 2.1and 48.1 ± 8.8 Kg respectively. Mean ± SD trough cyclosporin level at day 14 was 270 ± 55 ug/dl. After the first dose of E-MPS, mean (range) values of AUC0-12h for MPA and MPAG were 73.9 ± 49.5 ug.h/ml (31.9-190) and 406 ± 133 (243-646) ug.h/ml respectively. Mean ± SD ratio of MPAG / MPA AUC 0-12h was 7.2 (2.4-12.3). The mean ± SD of MPA AUC0-12h attained on day 14 was 74.3 ± 44.3 ug.h/ml. Mean ± SD value of trough MPA after the first dose on day 1 and day 14 were 2.9 ± 0.7 and 3.1 ± 0.8 ug/ml. Mean (range) C2 of cyclosporin on day 30 was 1254 ± 399 (808-2136) ug/dl. Mean ± SD of cyclosporin dosage was 4.6 ± 1.8 mg/kg/day at day 30. Mean achieved serum creatinine was 1.1 ± 0.4 mg/dl. Patient and graft survival rate was 100%. No episode of biopsy proven acute rejection was observed after a minimum observation time of 3 months. All patients tolerate initial dose of E-MPS well. Two patients (AUC0-12h of MPA = 31 and 125 respectively) developed significant diarrhea and need E-MPS dose reduction. Other complications that occurred included urinary tract infection (n = 2), CMV syndrome (n = 1) and reversible cyclosporin nephrotoxicity (n = 3). Conclusions: Standard dose E-MPS leads to immediate delivery of adequate therapeutic systemic MPA exposure in 100 % of patients from the first dose. This rapid rate of delivery is higher than that described previously.

Monitoring trough plasma concentrations of mycophenolate mofetil in patients with uveitis.

Mycophenolate mofetil (MMF) has been used successfully in patients with various forms of uveitis not responsive to other immunosuppressants. Nevertheless, for these patients neither recommendations for optimal dosage of MMF nor data concerning drug exposure of MMF are available. To describe the results of the therapeutic drug monitoring (TDM) of MMF trough concentrations in a cohort of patients with uveitis, with the aim of optimizing the dosage of this drug, by maintaining a target concentration to achieve adequate immunosuppression with a minimal risk of therapeutic failure or toxicity. This study describes the results of monitoring trough plasma concentrations of MMF in 12 patients with uveitis during a mean period of 21.4 months. Patients included one with Stevens-Johnson syndrome, one with Graves-Basedow's disease, one with Behcet's disease, one with idiopathic thrombocytopenic purpura and the rest with idiopathic uveitis. All patients were treated with steroids and additional therapy prior to treatment with MMF. Pharmacokinetic monitoring of mycophenolic acid (MPA) was performed with 108 trough plasma samples using an EMIT assay. Mean daily MMF dose was 24.5 +/- 6.3 mg/kg and mean trough MPA concentration was 2.9 +/- 1.9 microg/mL. Therapy was effective in 10 patients (83%). There were few side-effects: diarrhoea, excitement, agitation and cough that disappeared with daily dose reduction of MMF. MMF was effective in the majority of patients with uveitis with an acceptable profile of side-effects. TDM of MMF in patients with uveitis is clinically practicable and may help to optimize individual immunosuppressive therapy. We estimated that MMF dosages in the range of 0.5-1.5 g/day might be sufficient for treating uveitis and we recommend an initial target range of 2-4 microg/mL, which included 50% of our results. Randomized controlled trials are essential to confirm the efficacy of MMF in uveitis.

Plasma trough levels of mycophenolic acid do not correlate with efficacy and safety of mycophenolate mofetil in psoriasis

Mycophenolate mofetil (MMF) has been shown to be effective for systemic treatment of psoriasis. MMF is the prodrug of mycophenolic acid (MPA), the pharmacologically active compound. The measurement of plasma MPA levels could be useful for optimizing therapeutic management using MMF. To investigate whether plasma trough levels of MPA correlate with the efficacy and safety of oral MMF in the treatment of patients with psoriasis. Six patients (four women and two men, mean age 58 years) with severe chronic plaque-type psoriasis were treated with oral MMF 1 g twice daily. The Psoriasis Area and Severity Index (PASI), routine laboratory examinations and plasma MPA trough levels, measured by an enzyme-multiplied immunoassay (EMIT), were determined at 2 weeks and 1, 3, 5 and 7 months. All the patients experienced a marked improvement within the first 15 days and continued to do so for 5-7 months. Two patients achieved complete remission. MMF was well tolerated. MPA levels showed a wide intra- and interindividual variability. There was no significant correlation between MPA trough levels and the reduction of the PASI or the presence of adverse effects, but a good correlation with therapeutic compliance. The monitoring of MPA trough levels with EMIT appears to be a poor predictor of efficacy or toxicity. In contrast, it is a useful tool to evaluate the degree of therapeutic compliance.

Long-term changes in mycophenolic acid exposure in combination with tacrolimus and corticosteroids are dose dependent and not reflected by trough plasma concentration: a prospective study in 100 de novo renal allograft recipients.

Tacrolimus and cyclosporine A have different effects on exposure to concomitantly administered mycophenolate mofetil (MMF), measured as the mycophenolic acid (MPA) dose interval area under the plasma concentration versus time curve (AUC0-12 h) or the plasma MPA predose concentration (C0). This has led to recommendations in using a 50% lower dose of MMF in combination with tacrolimus compared to cyclosporin A. At present, no long-term data are available regarding the pharmacokinetics (PK) of different dosages of MMF in combination with tacrolimus and the clinical variables that influence the dose-exposure relationship of MPA. A prospective 12-month pharmacokinetic study was performed in 100 de novo renal transplant recipients treated with two different MMF dosages (1 g/day vs. 2 g/day) in combination with tacrolimus and corticosteroids. MPA AUC data were collected 7 days, 6 weeks, and 3 and 12 months posttransplantation, and model-independent PK parameters were calculated. Clinical variables that could possibly influence MPA PK were evaluated. The MPA AUC0-12 h significantly increased toward 6 weeks (p < 0.05) but only in the 2-g MMF dosing group. The MPA AUC0-12 h in the 1-g MMF group reached its nadir at 3 months, while in the 2-g MMF group, it remained elevated until 3 months, returning to baseline values by 12 months. This differential evolution in exposure was not only inadequately reflected by the corresponding MPA C0 concentrations, but the MPA C0 concentrations also were not significantly different between the two dosing groups at early postgrafting (day 7) and at 12 months. Using multiple stepwise regression analysis, C0 (r = 0.51, p < 0.0001) and end-of-dose interval MPA plasma concentration (C12: r2 = 0.61, p < 0.0001) were found to poorly predict MPA AUC0-12 h, while MPA plasma concentrations at 4 hours (C4: r2 = 0.85, p < 0.0001) and 6 hours postdosing (C6: r2 = 0.83, p < 0.0001) were superior but hampered by a large prediction bias and imprecision. An abbreviated 2-hour AUC measurement (r2 = 0.78), using three sampling points (C0, C40 [MPA plasma concentration 40 min postdosing], C2), provided the best compromise between a monitoring tool that is theoretically ideal and practically feasible. MPA pharmacokinetics were not influenced by recipient age, gender, and body weight or by serum albumin concentrations, allograft function, or corticosteroid or tacrolimus dose. Mild hepatic dysfunction early after grafting did result in significantly reduced MPA exposure (MPA AUC0-12 h, p = 0.01 and C0, p = 0.03). In this study, it was demonstrated for the first time that the dynamics of long-term MPA pharmacokinetics in combination with tacrolimus differ according to the daily MMF dose and that this effect is not adequately reflected by MPA trough concentrations. Using the latter as a routine measure for therapeutic drug monitoring might mislead clinicians into drawing wrong conclusions in terms of relating questions of efficacy or toxicity to MPA exposure.

Glucocorticoids interfere with mycophenolate mofetil bioavailability in kidney transplantation

Steroids have been shown to induce the hepatic glucuronyltransferase (GT) expression enhancing the activity of uridine diphosphate-GT, the enzyme responsible for mycophenolic acid (MPA) metabolism. The impact of steroids on MPA pharmacokinetics, however, has not been investigated to date. As a part of a steroid-sparing clinical trial, we studied the effect of steroids on MPA bioavailability in 26 kidney transplant recipients. Despite that the MMF dose did not change significantly with time, dose-normalized MPA AUC0-12h was lower during the first month (triple therapy, high doses of steroids) than at month 6 post-surgery (triple therapy, low maintenance dose of steroids (32.94 +/- 10.98 vs. 50.87 +/- 22.37 microg/mL. h; P < 0.01). During the steroid tapering and withdrawal phase (from month 6 to 21 post-Tx), plasma MPA trough and peak concentration as well as AUC0-12h progressively increased, while plasma MPA clearance and MPAG (the major MPA metabolite) trough levels declined. Renal function was stable throughout. Since cyclosporine A (CsA) may interfere with MPA pharmacokinetics, MPA and CsA also were measured in an additional control group of 12 kidney transplant patients at month 21 post-Tx who were still on triple therapy (MMF, CsA and steroids). Despite a similar CsA exposure, the control group had a significantly lower MPA AUC0-12h and higher MPAG trough concentration than patients on dual therapy at month 21 post-Tx. These findings indicate that steroids interfere with MPA bioavailability, and that discontinuation of the drug results in higher MPA exposure, which may compensate at least in part for the lower immunosuppressive level achieved with the remaining dual therapy with CsA and MMF.

Value of mycophenolic acid trough level monitoring after lung transplantation

Value of mycophenolic acid trough level monitoring after lung transplantation

Mycophenolic acid levels in pediatric heart transplant recipients receiving mycophenolate mofetil

Background Mycophenolate mofetil (MMF) is an immunosuppressive agent that has shown promise in adult patients who have undergone heart transplantation. There have been a number of studies of the pharmacokinetics of MMF in adult solid organ transplant recipients, but there is very little information in the pediatric population. The purpose of this study was to review our experience with MMF dosing and the role of mycophenolic acid (MPA) levels for therapeutic drug monitoring in a population of pediatric heart transplant recipients. Methods Data were obtained by review of the pediatric heart transplant database between November 1, 1997 and October 15, 1998. The data included all serum trough MPA levels, patient age, weight, height, indication for and dose of MMF, other medications, and details of all episodes of graft rejection. Results Forty-four patients (27 males) had a total of 128 serum trough MPA levels. Median age at transplant was 2.7 years (7 days to 18.4 years), and at time of review was 6.3 years (29 days to 23.5 years). MMF treatment was used for induction in 18 patients, induction and rejection in 23 patients and graft vasculopathy in 3 patients. Dosing by body surface area (mg/m 2), age and interval from transplantation were all independently associated with MPA level. There was a trend toward requiring higher doses to achieve desired levels (>3 ng/ml) in younger patients. The average dose to achieve desired levels was higher in the immediate post-transplant period. There was a trend that MPA levels for a given dose were higher in patients on concurrent tacrolimus therapy. Conclusions (1) There is marked individual variation in pharmacokinetics of MMF in pediatric patients; (2) dosing by body surface area may be advantageous; (3) higher MMF doses may be required at younger ages and in the early period after transplantation; (4) lower MMF doses may be required with concurrent tacrolimus therapy; and (5) serum trough MPA levels may relate to efficacy. Therefore, therapeutic drug monitoring of serum trough MPA levels may be required for individualized MMF dosing in pediatric cases.

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.

Correlation of Mycophenolic Acid Pharmacokinetic Parameters with Side Effects in Kidney Transplant Patients Treated with Mycophenolate Mofetil

Mycophenolate mofetil (MMF) is widely used in organ transplantation to prevent acute rejection. Because MMF can produce hematologic and/or gastrointestinal toxicity, therapeutic monitoring is becoming mandatory. This study was designed to investigate the relationship between the clinical events and the pharmacokinetics of mycophenolic acid (MPA) in adult renal transplantation. Thirty-one adult kidney recipients were prospectively included in the study. MPA pharmacokinetic profiles (blood sampling at 0, 0.5, 1, 2, 4, 6, and 12 h after MMF oral dose) were obtained after transplantation (desired creatinine clearance, 40 mL/min), at 3 months after grafting, and at every clinical event (e.g., side effect or rejection). All patients received a 10-day course of anti-thymocyte globulin, cyclosporine, MMF (1 g twice daily), and steroids. We divided the 31 patients into two groups (groups 1 and 2). Ten patients (32%; group 1) had uneventful outcomes, and 21 patients (68%; group 2) presented with MPA-related side effects. For groups 1 and 2, the MPA trough concentrations (C(min)) were 1.63 +/- 1.07 and 2.29 +/- 1.16 mg/L, respectively (P = 0.06), and the areas under the curve (AUCs) for MPA from t(0) to t(12 h) (MPA-AUC(0-12h)) were 39.80 +/- 15.29 and 62.10 +/- 21.07 mg. h/L, respectively (P = 0.0005, two-sample t-test). Three patients experienced acute graft rejection after the oral MMF dose was reduced because of side effects. In this group, the MPA-C(min) and MPA-AUC were significantly lower by the time acute rejection occurred (1.00 +/- 0.45 mg/L and 25.00 +/- 6.20 mg. h/L, respectively). At a fixed dose (1 g twice per day), we compared the pharmacokinetic parameters of MPA [C(min), the MPA concentration 30 min after the oral dose of MMF (C(30)), and AUC] according to the presence or absence of side effects in the two groups. C:(min) and AUC did not differ between the two groups [C(min) = 2.22 +/- 1.13 vs 2.17 +/- 1.13 mg/L (P = 0.9); AUC = 66.82 +/- 29.87 vs 55.70 +/- 11.74 mg. h/L (P = 0.11)]; and C(30) was significantly higher in group 2 than in group 1 (C(30) = 32.99 +/- 12.59 vs 7.45 +/- 5.40 mg/L; P <0.0001). Our results demonstrate a pharmacokinetic/pharmacodynamic relationship between MPA and clinical events. At a fixed dose of 2 g/day, a high C(30) is associated with increased risk for side effects. This study suggests that dividing the MMF daily oral dose into more than two divided doses might prevent early MPA toxicity.