Gelder, T. van

Doubt about the feasibility of preemptive genotyping (Article)

2013-03-01T00:00:00Z

Individualization of tamoxifen treatment for breast carcinoma (Article)

2012-10-01T00:00:00Z

Traditionally, all patients treated with tamoxifen receive a standard dose. A number of studies claimed a clinically relevant impact of cytochrome P450 2D6 (CYP2D6) genotype on outcome, and therefore genotyping before tamoxifen therapy was advocated. Recent data showed that adequate exposure to the active metabolite endoxifen is important and that genotype only partially explains interindividual differences in endoxifen concentrations. Phenotyping approaches, as well as therapeutic drug monitoring (TDM) strategies, are now being tested to individualize tamoxifen treatment.

Quantification of tamoxifen and three of its phase-I metabolites in human plasma by liquid chromatography/triple-quadrupole mass spectrometry (Article)

2011-12-15T00:00:00Z

In view of future pharmacokinetic studies, a highly sensitive ultra performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method has been developed for the simultaneous quantification of tamoxifen and three of its main phase I metabolites in human lithium heparinized plasma. The analytical method has been thoroughly validated in agreement with FDA recommendations. Plasma samples of 200μl were purified by liquid-liquid extraction with 1ml n-hexane/isopropanol, after deproteination through addition of 50μl acetone and 50μl deuterated internal standards in acetonitrile. Tamoxifen, N-desmethyl-tamoxifen, 4-hydroxy-tamoxifen and endoxifen were chromatographically separated on an Acquity UPLC®BEH C18 1.7μm 2.1mm×100mm column eluted at a flow-rate of 0.300ml/min on a gradient of 0.2mM ammonium formate and acetonitrile, both acidified with 0.1% formic acid. The overall run time of the method was 10min, with elution times of 2.9, 3.0, 4.1 and 4.2min for endoxifen, 4-hydroxy-tamoxifen, N-desmethyl-tamoxifen and tamoxifen, respectively. Tamoxifen and its metabolites were quantified by triple-quadrupole mass spectrometry in the positive ion electrospray ionization mode. The multiple reaction monitoring transitions were set at 372>72 (m/z) for tamoxifen, 358>58 (m/z) for N-desmethyl-tamoxifen, 388>72 (m/z) for 4-hydroxy-tamoxifen and 374>58 (m/z) for endoxifen. The analytical method was highly sensitive with the lower limit of quantification validated at 5.00nM for tamoxifen and N-desmethyl-tamoxifen and 0.500nM for 4-hydroxy-tamoxifen and endoxifen, which is equivalent to 1.86, 1.78, 0.194 and 0.187ng/ml for tamoxifen, N-desmethyl-tamoxifen, 4-hydroxy-tamoxifen and endoxifen, respectively. The method was also precise and accurate, with within-run and between-run precisions within 12.0% and accuracy ranging from 89.5 to 105.3%. The method has been applied to samples from a clinical study and cross-validated with a validated LC-MS/MS method in serum.

Measurement of cyclosporine A in rat tissues and human kidney transplant biopsies - A method suitable for small (<1 mg) samples (Article)

2011-12-01T00:00:00Z

Therapeutic drug monitoring is used to individualize cyclosporine A (CsA) dosing after transplantation. However, immunosuppressant concentrations within the graft may better predict clinical outcomes, including toxicity. This study aimed to develop a method suitable for CsA measurement using routine fineneedle biopsy samples. CsA was quantified retrospectively in kidney and liver tissues from 10 rats administered CsA, and 21 core needle kidney biopsies taken from renal transplant patients with suspected graft dysfunction. Dried biopsies were weighed (mean ± SD weights of 0.22 ± 0.18 mg), enzymatically solubilized, and then CsA was extracted and quantified using online 2-dimensional liquid chromatography-tandem mass spectrometry. The method was linear (r2> 0.997, n = 10), accurate, and precise (quality control and calibrator coefficient of variation and bias <15%), with minimal matrix effects (coefficient of variation and bias < 15%). Reproducibility of tissue weight measurements was confirmed by retrospective DNA quantitation, with a significant linear correlation between weight and total DNA concentration (r2= 0.988). In rats, there was a significant linear correlation between CsA concentrations in liver and kidney tissues (r2= 0.996) but there was no correlation between blood (C0) and tissue CsA concentrations (Spearman r = 0.430 and 0.503, P > 0.05). Similarly, in 16 transplant patients, for whom blood CsA concentrations (C2) were available within 1 day of the renal biopsy being performed, there was no significant correlation between CsA concentrations in blood and kidney tissue (Spearman r = 0.168, P > 0.05). In situ CsA measurements acquired using this method could make an easy transition into clinical use due to their retrospective nature and minimal disruption to current clinical protocols and could provide an additional tool for optimizing clinical outcomes in the future. Copyright

De patient bestaat niet (Inaugural Lecture)

2011-09-16T00:00:00Z

Rede, Uitgesproken bij aanvaarding van van het ambt van bijzonder hoogleraar met als leeropdracht klinische farmacologie aan het Erasmus MC, faculteit van de Erasmus Universiteit Rotterdam op 16 september 2011. De klinische farmacologie is de wetenschap die zich bezighoudt met het bestuderen van de toepassing van geneesmiddelen bij de mens. De basis wordt gevormd door kennis over de werkingsmechanismen van geneesmiddelen en de pathofysiologie van ziektebeelden. De klinische farmacologie verbindt als het ware de basale farmacologische principes met de klinische praktijk. Het uiteindelijke doel is het beter inzetten van geneesmiddelen bij de behandeling van patiënten, waarbij gestreefd wordt naar optimale effectiviteit en naar het beperken van bijwerkingen. De veronderstelling dat geneeskunde en farmacie hierbij gecombineerd worden is dus ook niet zo gek. Sterker nog, om de klinische farmacologie optimaal te benutten is een nauwe samenwerking tussen artsen en apothekers van groot belang.

Imatinib treatment duration is related to decreased estimated glomerular filtration rate in chronic myeloid leukemia patients (Article)

2011-09-01T00:00:00Z

Background: We analyzed the incidence of acute kidney injury and chronic renal failure in chronic myeloid leukemia (CML) patients using imatinib and investigated whether there is a relation between duration of imatinib therapy and decrease in estimated glomerular filtration rate (GFR). Patients and methods: One hundred five CML patients on imatinib therapy were enrolled. Creatinine, urea, uric acid, and potassium measurements from imatinib treatment onset until the end of follow-up (median 4.5 years) were included in the analysis. GFR was estimated using the Chronic Kidney Disease Epidemiology Collaboration equation. Results: During follow-up,7%of patients developed acute kidney injury; creatinine levels returned to baseline in only one of them. According to the regression equation, the mean baseline value of the estimated GFR was 88.9 ml/min/1.73m2. Estimated GFR decreased significantly with imatinib treatment duration; the mean decrease per year was 2.77 ml/min/1.73 m2(P < 0.001); 12% of patients developed chronic renal failure. Age, hypertension, and a history of chronic renal failure or interferon usage were not significantly related to the mean decrease in the estimated GFR over time. Conclusion: The introduction of imatinib therapy in nonclinical trial CML patients is associated with potentially irreversible acute renal injury, and the long-term treatment may cause a clinically relevant decrease in the estimated GFR.

Therapeutic drug monitoring for mycophenolic acid is value for (Little) money (Article)

2011-08-01T00:00:00Z

Relationship of tacrolimus exposure and mycophenolate mofetil dose with renal function after renal transplantation (Article)

2011-07-15T00:00:00Z

Introduction: The most common immunosuppressive treatment in de novo renal transplantation is a triple regimen that includes tacrolimus, mycophenolate mofetil (MMF) and corticosteroids, and that may also include antibody induction. Whether nephrotoxicity is an issue with tacrolimus at the currently used dosages remains an open question. Methods: We pooled data from three large, randomized, de novo renal transplantation studies (Symphony, Fixed Dose Concentration Controlled [FDCC], and OptiCept) that used variations of the triple regimen with respect to tacrolimus target levels, MMF dosing, and antibody induction. We used multivariate linear regression to explore the relationship of renal function at 1 year after transplantation (estimated glomerular filtration rate) with tacrolimus levels and MMF dose measured over the previous 6 months. The model included also a series of possible confounders. Results: The analysis population consisted of 998 patients. On average, tacrolimus levels were in a range considered low (mean±standard deviation 7.2±2.54 ng/mL), and MMF dose was 1.5±0.61 g/day. Lower tacrolimus levels and higher MMF doses were associated with significantly better renal function. There were other variables associated with renal function, most notably acute rejection, donor age, and delayed graft function. Subanalyses in each of the three studies gave a consistent picture. There was no overt difference in the effect sizes when patients with stage II (estimated glomerular filtration rate 60-89 mL/min) or stage III (30-59 mL/min) chronic kidney disease were assessed separately. CONCLUSION.: Tacrolimus seems to have a moderate but consistent nephrotoxic effect even in modern efficient immunosuppressive regimens where it is used at lower doses than in previous years.

CYP3A5 genotype is not related to the intrapatient variability of tacrolimus clearance (Article)

2011-06-01T00:00:00Z

Background: The risk of long-term chronic allograft nephropathy and graft loss after kidney transplantation is increased in patients with a high intrapatient variability of tacrolimus (Tac) clearance. Methods: To test whether this intrapatient variability is associated with an individual's CYP3A5 genotype, we measured the intrapatient variability in Tac clearance in a cohort of 208 kidney transplant recipients treated with Tac and mycophenolate mofetil. Results: Tac dose requirement was significantly higher in patients expressing CYP3A5. However, intraindividual variability of Tac clearance was not related to CYP3A5 genotype. Conclusions: Intraindividual variability in Tac clearance is not related to CYP3A5 genotype. Other factors, including patient adherence, may explain the variability in Tac clearance within an individual patient over time. Copyright

Dried blood spot UHPLC-MS/MS analysis of oseltamivir and oseltamivircarboxylate-a validated assay for the clinic (Article)

2011-05-03T00:00:00Z

The neuraminidase inhibitor oseltamivir (Tamiflu®) is currently the first-line therapy for patients with influenza virus infection. Common analysis of the prodrug and its active metabolite oseltamivircarboxylate is determined via extraction from plasma. Compared with these assays, dried blood spot (DBS) analysis provides several advantages, including a minimum sample volume required for the measurement of drugs in whole blood. Samples can easily be obtained via a simple, non-invasive finger or heel prick. Mainly, these characteristics make DBS an ideal tool for pediatrics and to measure multiple time points such as those needed in therapeutic drug monitoring or pharmacokinetic studies. Additionally, DBS sample preparation, stability, and storage are usually most convenient. In the present work, we developed and fully validated a DBS assay for the simultaneous determination of oseltamivir and oseltamivircarboxylate concentrations in human whole blood. We demonstrate the simplicity of DBS sample preparation, and a fast, accurate and reproducible analysis using ultra high-performance liquid chromatography coupled to a triple quadrupole mass spectrometer. A thorough validation on the basis of the most recent FDA guidelines for bioanalytical method validation showed that the method is selective, precise, and accurate (≤15% RSD), and sensitive over the relevant clinical range of 5-1,500 ng/mL for oseltamivir and 20-1,500 ng/mL for the oseltamivircarboxylate metabolite. As a proof of concept, oseltamivir and oseltamivircarboxylate levels were determined in DBS obtained from healthy volunteers who received a single oral dose of Tamiflu®.

Pediatric aspects of therapeutic drug monitoring of mycophenolic acid in renal transplantation (Article)

2011-04-01T00:00:00Z

Mycophenolate mofetil (MMF) is widely used for maintenance immunosuppressive therapy in pediatric renal and heart transplant recipients. Children undergo developmental changes (ontogeny) of drug disposition, which may affect drug metabolism of the active compound mycophenolic acid (MPA). Therefore, a detailed characterization of MPA pharmacokinetics and pharmacodynamics in this patient population is required. In general, the overall efficacy and tolerability of MMF in pediatric patients appear to be comparable with those in adults, except for a higher prevalence of gastrointestinal adverse effects in children younger than 6 years. The currently recommended dose in pediatric patients with concomitant cyclosporine is 1200 mg/m2per day in 2 divided doses; the recommended MMF dose with concomitant tacrolimus or without a concurrent calcineurin inhibitor is 900 mg/m2per day in 2 divided doses. Recent data suggest that fixed MMF dosing results in MPA underexposure (MPA-area under the concentration-time curve (AUC0-12), <30 mg × h/L) early posttransplant in approximately 60% of patients. To achieve adequate MPA exposure in most patients, an initial MMF dose of 1800 mg/m2per day with concomitant cyclosporine and 1200 mg/m2per day with concomitant tacrolimus for the first 2 to 4 weeks posttransplant has been suggested. As in adults, there is an approximately 10-fold variability in dose-normalized MPA-AUC0-12values between pediatric patients after renal transplantation, strengthening the argument for concentration-controlled dosing of the drug. Although the clinical utility of therapeutic drug monitoring of MPA for graft outcome and patient survival is still controversial, potential indications are the avoidance of underimmunosuppression, particularly in patients with high immunologic risk in the initial period posttransplant, in patients who are treated with protocols that explore the possibilities of calcineurin inhibitor minimization, withdrawal or even complete avoidance, and steroid withdrawal or avoidance regimens that might also benefit from intensified therapeutic drug monitoring of MPA. An additional indication especially in adolescent patients is the monitoring of drug adherence. Therapeutic drug monitoring of MPA in pediatric solid organ transplantation using limited sampling strategies is preferable over drug dosing based on trough level monitoring only. Several validated pediatric limited sampling strategies are available. Clearly, more research is required to determine whether pediatric patients will benefit from therapeutic drug monitoring of MPA for long-term maintenance immunosuppression with MMF.

Therapeutic drug monitoring of mycophenolates: Why make simple things complicated? (Article)

2011-04-01T00:00:00Z

Mycophenolate monitoring in liver, thoracic, pancreas, and small bowel transplantation: A consensus report (Article)

2011-04-01T00:00:00Z

Assessing the value of mycophenolic acid (MPA) monitoring outside renal transplantation is hindered by the absence of any trial comparing fixed-dose and concentration-controlled therapy. However, in liver and thoracic transplantation particularly, clinical trials, observational studies with comparison groups, and case series have described MPA efficacy, exposure/efficacy relationships, pharmacokinetic variability, and clinical outcomes relating to plasma MPA concentrations. On the basis of this evidence, this report identifies MPA as an immunosuppressant for which the combination of variable disposition, efficacy, and adverse effects contributes to interindividual differences seemingly in excess of those optimal for a fixed-dosage mycophenolate regimen. Combined with experiences of MPA monitoring in other transplant indications, the data have been rationalized to define circumstances in which measurement of MPA concentrations can contribute to improved management of mycophenolate therapy in nonrenal transplant recipients.

Therapeutic drug monitoring of mycophenolates in kidney transplantation: Report of The Transplantation Society consensus meeting (Article)

2011-04-01T00:00:00Z

Mycophenolate, clinical pharmacokinetics, formulations, and methods for assessing drug exposure (Article)

2011-04-01T00:00:00Z

This article summarizes part of a consensus meeting about mycophenolate (MPA) therapeutic drug monitoring held in Rome under the auspices of The Transplantation Society in November 2008 (Clin J Am Soc Nephrol. 2010;5:341-358). This part of the meeting focused on the clinical pharmacokinetics of MPA and included discussion on how to measure MPA (active drug) exposure and the differences between the currently available formulations. Summary points: • Because of variability in the dose-concentration relationship, MPA exposure should be measured and doses should be adjusted accordingly to achieve optimal clinical outcomes. • Suggested therapeutic exposures derived for MPA from mycophenolate mofetil (MMF) may differ to those that could be useful for MPA from enteric-coated mycophenolate sodium (EC-MPS), particularly if limited sampling strategies or single concentration, especially trough concentrations, is used, as the concentration-time profiles of MPA from the 2 formulations are quite different. The 2 MPA formulations cannot be considered as bioequivalent. • The area under the concentration-time curve (AUC0-12) is considered the criterion standard for monitoring of MPA, which is a reflection of exposure to the drug over the entire dosing period. If a limited sampling protocol coupled with multilinear regression or Bayesian estimation is used to estimate this parameter, it should be used only for the population in which the model has been developed and should preferably include at least one time point after 4 hours (preferably around 8 or 9 hours after MMF dosing). If a single time point is to be used as a surrogate for an AUC0-12, trough concentration of MPA may be the most practical but, from a pharmacokinetic standpoint, is not the most informative time point to choose. • Because limited sampling strategies to estimate MPA exposure from EC-MPS have not yet been well developed and fully evaluated, nor have accurate Bayesian estimators been reported, AUC0-12measurement is still necessary to obtain reliable estimates of MPA exposure in patients treated with EC-MPS. The measurement of MPA trough concentrations should not be used at all for MPA exposure assessment following administration of EC-MPS. • Lower (or higher) than expected total MPA exposure in patients with severe renal impairment may still indicate sufficient free MPA exposure. Mycophenolate free exposure measurement/estimation is likely to be beneficial in patients with severe renal impairment (creatinine clearance <25 mL/min) to guide dosage estimation, especially because renal function changes over time after transplant, while recognizing that robust prospective studies to show the clinical advantage of measuring free MPA exposure are still required. • Lower total measured MPA exposure in patients with hypoalbuminemia may still indicate sufficient free MPA exposure. Mycophenolate free concentration measurement and estimation of exposure are likely to be beneficial in patients with a serum albumin less than or equal to 31 g/L to guide interpretation of MPA exposure. • A 1.5-g twice-daily starting dose of MMF rather than a 1-g twice-daily starting dose of MMF is more likely to achieve the minimum target MPA exposure in adult transplant recipients receiving concomitant cyclosporine therapy. Because the cyclosporine dose is progressively tapered following transplantation, MPA exposure should be measured repeatedly and MMF should be doses adjusted accordingly to achieve optimal clinical outcome. • Mycophenolate exposure should be measured in the first week after transplant, then each week for the first month, each month until month 3, and subsequently every 3 months up to 1 year with appropriate dosage adjustment, as AUC is likely to increase over time. After 1 year, if dosage requirement has stabilized, MPA exposure can be assessed each time the immunosuppressive regimen is changed or a potentially interacting drug is introduced or withdrawn. • Assessment of UGT1A9 single nucleotide polymorphisms (-275T>A, -2152C>T, -440C>T, -331T>C) should be considered before transplantation to assist in dosing decisions to achieve optimal MPA exposure immediately after transplant. Consideration of the points summarized above should lead to more effective dosage adjustment based on sound applied pharmacokinetic and pharmacodynamic principles.

Nonlinear relationship between mycophenolate mofetil dose and mycophenolic acid exposure: Implications for therapeutic drug monitoring (Article)

2011-03-01T00:00:00Z

Background and objectives: Mycophenolate mofetil (MMF) is an immunosuppressive drug used in renal transplant patients. Upon oral administration it is hydrolyzed to the active agent mycophenolic acid (MPA). In renal transplant recipients, MMF therapy is optimal when the area under the curve of MPA is 30 to 60 mg·h/L. When MMF doses are adjusted, a linear relationship between dose and MPA exposure is assumed. In this study, the linearity of MMF pharmacokinetics was investigated. Design, setting, participants, & measurements: MPA concentration-time profiles from renal transplant recipients cotreated with cyclosporine (n = 140) or tacrolimus (n = 101) were analyzed retrospectively using nonlinear mixed-effects modeling. The correlation between the MMF dose and the pharmacokinetics parameters was evaluated. Results: In the developed population pharmacokinetics model MPA clearance and the central volume of distribution were correlated with cyclosporine coadministration and time posttransplantation. The pharmacokinetics of MPA were not linear. Bioavailability decreased with increasing MMF doses. Compared with an MMF dose of 1000 mg (=100%), relative bioavailability was 123%, 111%, 94%, and 90% in patients receiving MMF doses of 250, 500, 1500, and 2000 mg in combination with cyclosporine (P < 0.001); respective values in tacrolimus-cotreated patients were 176%, 133%, 85%, and 76% (P < 0.001). Because of the decreasing relative bioavailability, MPA exposure will increase less than proportionally with increasing MMF doses. Conclusions: MMF exhibits nonlinear pharmacokinetics. This should be taken into account when performing therapeutic drug monitoring. Copyright

Comparison of MMF efficacy and safety in paediatric vs. adult renal transplantation: Subgroup analysis of the randomised, multicentre FDCC trial (Article)

2011-03-01T00:00:00Z

Background: Mycophenolate mofetil (MMF) is widely used for immunosuppressive therapy in renal transplantation, but comparative data regarding efficacy and safety in paediatric vs. adult kidney allograft recipients in one and the same study are lacking.Methods. We therefore performed this subgroup analysis of the FDCC trial, a 12-month, prospective, randomised study, comparing fixed-dose (FD) with concentration-controlled (CC) MMF dosing in paediatric and adult renal transplant recipients. Sixty-two paediatric and 839 adult de novo patients in 19 countries were randomised 1:1 to receive fixed-dose or concentration-controlled MMF therapy in combination with calcineurin inhibitors and corticosteroids.Results. Both patient and allograft survival proved to be excellent in paediatric patients (98.4% and 90.3%) and adults (96.8% and 95.0%). The rates of biopsy-proven acute rejections (BPAR) and treated acute rejection episodes (ARE) were comparable between paediatric (12.9% and 17.7%) and adult patients (15.5% and 20.7%). Transplant function at 12 months post-transplant was similar in paediatric (67.8 ± 45.6 mL/min/1.73 m) and adult recipients (64.7 ± 23.3 mL/min/1.73 m). Children < 6 years (n = 10) exhibited a numerically higher frequency of leucocytopaenia (20%), diarrhoea (40%) and weight loss (10%) than older children (618 years; 5.8%, 28.8% and 1.9%) and adults (16.1%, 24.7% and 1.5%). On the whole, the percentage of patients who experienced adverse events causing interruption of MMF therapy were numerically lower in children (4.8%) than in adults (12.5%).Conclusions. The overall efficacy and tolerability of MMF appear to be comparable between paediatric and adult patients. Further studies are needed to validate these results.

Differences in clearance of mycophenolic acid among renal transplant recipients, hematopoietic stem cell transplant recipients, and patients with autoimmune disease (Article)

2010-10-01T00:00:00Z

For more than a decade, mycophenolate mofetil (MMF) has been used as an immunosuppressive drug in solid organ transplant recipients to prevent graft rejection. After oral administration, the prodrug MMF is rapidly hydrolyzed to the active metabolite mycophenolic acid (MPA). MMF is being used increasingly in hematopoietic stem cell transplantation (HSCTx) and autoimmune diseases (AID). The pharmacokinetics of MPA are markedly different in these patients. In comparison with renal transplant recipients (RTx), MPA clearance is increased in HSCTx patients and decreased in AIDS. The aim of this study was to characterize MPA clearance in RTx, HSCTx, and AID patients and to test whether the differences in clearance can be described by clinical chemical parameters. MPA concentration-time profiles from 19 RTx patients coprescribed cyclosporine, 17 RTx patients coprescribed tacrolimus, 38 HSCTx patients coprescribed cyclosporine, and 36 patients with AID were analyzed retrospectively with nonlinear mixed effects modeling (first-order conditional estimate). The following covariates were tested: indication for MMF treatment, sex, age, weight, plasma albumin, cyclosporine cotreatment, dose and predose blood concentration, creatinine clearance, and hemoglobin. Pharmacokinetics of MPA were described by a two-compartment model with time-lagged first-order absorption. MPA clearance was correlated in univariate analysis with plasma albumin, cyclosporine dose and predose blood concentration, creatinine clearance, hemoglobin, and indication for MMF treatment (RTx, HSCTx, or AID) (P < 0.001). All significant covariates were combined in an intermediate multivariate model followed by backward elimination. The indication for MMF treatment could be removed from the intermediate model without compromising the fit. The correlation between clearance and cyclosporine predose concentrations and plasma albumin remained significant in the final model and could describe the difference in clearance between the different indications for MMF treatment. Median clearance was 30.2, 45.6, and 10.7 L/h in RTx, HSCTx, and AID patients, respectively. In conclusion, plasma albumin concentrations and cyclosporine predose concentrations are able to describe the difference in MPA clearance among RTx, HSCTx, and AID patients. Copyright

The impact of CYP2D6-predicted phenotype on tamoxifen treatment outcome in patients with metastatic breast cancer (Article)

2010-09-07T00:00:00Z

Abstract BACKGROUND: Cytochrome P450 2D6 (CYP2D6) has a crucial role in the metabolic conversion of tamoxifen into the active metabolite endoxifen. In this cohort study, the effect of CYP2D6-predicted phenotype, defined as the combined effect of CYP2D6 genetic variation and concomitant use of CYP2D6-inhibiting medication, on time to breast cancer progression (TTP) and overall survival (OS) in women who use tamoxifen for metastatic breast cancer (MBC) was examined. METHODS: We selected patients treated with tamoxifen (40 mg per day) for hormone receptor-positive MBC from whom a blood sample for pharmacogenetic analysis (CYP2D6*3, *4, *5, *6, *10 and *41) was available. Patient charts (n=102) were reviewed to assess TTP and OS, and to determine whether CYP2D6 inhibitors were prescribed during tamoxifen treatment. RESULTS: OS was significantly shorter in patients with a poor CYP2D6 metaboliser phenotype, compared with extensive metabolisers (HR=2.09; P=0.034; 95% CI: 1.06-4.12). Co-administration of CYP2D6 inhibitors alone was also associated with a worse OS (HR=3.55; P=0.002; 95% CI: 1.59-7.96) and TTP (HR=2.97; P=0.008; 95% CI: 1.33-6.67) compared with patients without CYP2D6 inhibitors. CONCLUSION: CYP2D6 phenotype is an important predictor of treatment outcome in women who are receiving tamoxifen for MBC. Co-administration of CYP2D6 inhibitors worsens treatment outcome of tamoxifen and should therefore be handled with care.

Polymorphisms in type i and II inosine monophosphate dehydrogenase genes and association with clinical outcome in patients on mycophenolate mofetil (Article)

2010-09-01T00:00:00Z

Background: Type I and II inosine monophosphate dehydrogenases (IMPDH) are the targets of mycophenolic acid (MPA), a widely used immunosuppressant. The aims of this study were: to check the presence of controversial polymorphisms in the IMPDH II gene; to look for new ones; and to investigate potential associations between the most frequent SNPs in both IMPDH genes and clinical outcome in renal transplant recipients. Methods: The DNA and clinical data of 456 patients from two clinical trials were collected. We sequenced the IMPDH II gene in 80 patients and we genotyped the 456 patientsÊ DNA for the IMPDH II rs4974081, rs11706052, 787C>T and the IMPDH I rs2278293 and rs2278294 SNPs, all of which were earlier reported to be potentially involved in MPA treatment related outcome. We investigated the associations of biopsy proven acute rejection (BPAR), leucopenia, cytomegalovirus infections and other infections with these IMPDH polymorphisms, as well as with demographic, biological and treatment data using multivariate analysis. Results: Many IMPDH II variant alleles referenced in Genbank were not detected and no new polymorphisms were identified. In the whole group of 456 patients, the IMPDH I rs2278294 SNP was associated with a lower risk of BPAR and a higher risk of leucopenia over the first year post-transplantation. No other IMPDH I or IMPDH II polymorphism was significantly associated with any clinical outcome. Interestingly, calcineurin inhibitor and MPA exposures below the therapeutic range increased the risk of BPAR. Cytomegalovirus infection was the factor most closely linked with leucopenia, whereas tacrolimus was associated with fewer infections than cyclosporine. Conclusion: IMPDH II genotyping may not improve MPA treatment outcome over the first year post-transplantation, in contrast to MPA and calcineurine inhibitor therapeutic drug monitoring and IMPDH I genotyping.

High within-patient variability in the clearance of tacrolimus is a risk factor for poor long-term outcome after kidney transplantation (Article)

2010-08-01T00:00:00Z

Background. We hypothesized that a high within-patient variability in clearance of tacrolimus and mycophenolate mofetil (MMF) would put patients at risk for periods of over- or underimmunosuppression and would thus lead to long-term chronic allograft nephropathy and graft loss after transplantation.Methods. From 297 patients transplanted between 1 January 2000 and 31 December 2004, the within-patient variability in clearance was calculated from tacrolimus whole-blood concentrations and mycophenolic acid (MPA) plasma concentrations drawn between 6 and 12 months post-transplantation. As a primary outcome, a composite end point consisting of graft loss, biopsy-proven chronic allograft nephropathy and 'doubling in plasma creatinine concentration in the period between t = 12 months post-transplantation and last follow-up' was used.Results. In the study population of 297 patients, 34 patients reached the primary end point of graft failure. The within-patient variability in the clearance of tacrolimus and three other covariates are significant risk factors for reaching the composite end point of failure [P-values for intraindividual tacrolimus variability = 0.003, biopsy-proven acute rejection (BPAR) = 0.003, recipient age at transplantation = 0.005]. The mean tacrolimus concentration for controls [7.4 (± 2.9) ng/mL] and for failures [6.9 (± 2.5) ng/mL] was similar. Within-patient variability in the clearance of MPA was not related to reaching the composite end point of failure.Conclusions. This study shows a significant relationship between the high within-patient variability in the clearance of tacrolimus, but not for MPA, and long-term graft failure.

The pharmacogenetics of calcineurin inhibitor-related nephrotoxicity (Article)

2010-08-01T00:00:00Z

Chronic calcineurin inhibitor (CNI)-induced nephrotoxicity is associated with prolonged use of cyclosporine and tacrolimus and has been observed after all types of transplantation, as well as during treatment of autoimmune disease. Extensive alterations in the renal architecture including glomerular sclerosis, tubular atrophy and interstitial fibrosis may lead to end-stage renal failure. Increasing evidence shows that pharmacogenetic factors explain part of the between-patient differences in susceptibility to developing CNI-induced nephrotoxicity. In this paper this evidence is reviewed, with special emphasis on the role of genetic factors influencing metabolism and transportation of CNIs in both acceptor and donor.

Dosing tacrolimus based on CYP3A5 genotype: Will it improve clinical outcome? (Article)

2010-06-01T00:00:00Z

Tacrolimus, widely used to prevent acute rejection following solid-organ transplantation, has become the cornerstone of immunosuppressive therapy after kidney transplantation. More than 70% of all renal transplant recipients receive this remarkably effective agent. 1 But tacrolimus is also highly toxic, and there is great between-patient variability in its pharmacokinetics. This, combined with a low therapeutic index, mandates routine therapeutic drug monitoring in clinical practice. 2 Typically, predose concentrations are monitored and the dose is adjusted to aim for target values that depend on immunological risk, comedication, and time since transplantation.

TDM for mycophenolic acid at no extra cost (Article)

2010-05-27T00:00:00Z

Understanding handling of drug safety alerts: a simulation study (Article)

2010-05-01T00:00:00Z

Purpose: To study correctness of drug safety alert handling and error type in a computerized physician order entry (CPOE) system in a simulated work environment. Methods: Disguised observation study of 18 physicians (12 from internal medicine and 6 from surgery) entering 35 orders of predefined patient cases with 13 different drug safety alerts in a CPOE. Structured interviews about how the generated drug safety alerts were handled in the simulation test and resemblance of the test to the normal work environment. Handling and reasons for this were scored for correctness and error type. Results: Thirty percent of alerts were handled incorrectly, because the action itself and/or the reason for the handling were incorrect. Sixty-three percent of the errors were categorized as rule based and residents in surgery used incorrect justifications twice as often as residents in internal medicine. They often referred to monitoring of incorrect substances or parameters. One alert presented as a second alert in one screen was unconsciously overridden several times. One quarter of residents showed signs of alert fatigue. Conclusion: Although alerts were mainly handled correctly, underlying rules and reasoning were often incorrect, thereby threatening patient safety. This study gave an insight into the factors playing a role in incorrect drug safety alert handling that should be studied in more detail. The results suggest that better training, improved concise alert texts, and increased specificity might help. Furthermore, the safety of the predefined override reason 'will monitor' and double alert presentation in one screen is questioned.

Functionality test for drug safety alerting in computerized physician order entry systems (Article)

2010-04-01T00:00:00Z

Purpose: To evaluate the functionality of drug safety alerting in hospital computerized physician order entry (CPOE) systems by a newly developed comprehensive test. Methods: Comparative evaluation of drug safety alerting quality in 6 different CPOEs used in Dutch hospitals, by means of 29 test items for sensitivity and 19 for specificity in offices of CPOE system vendors. Sensitivity and specificity were calculated for the complete test, and for the categories "within-order checks", "patient-specific checks", and "checks related to laboratory data and new patient conditions". Qualitative interviews with 16 hospital pharmacists evaluating missing functionality and corresponding pharmacy checks. Results: Sensitivity ranged from 0.38 to 0.79 and specificity from 0.11 to 0.84. The systems achieved the same ranking for sensitivity as for specificity. Within-order checks and patient-specific checks were present in all systems; alert generation or suppression due to laboratory data and new patient conditions was largely absent. Hospital pharmacists unanimously rated checks on contra-indications (absent in 2 CPOEs) and dose regimens less than once a day (absent in 4 CPOEs) as important. Pharmacists' opinions were more divergent for other test items. A variety of pharmacy checks were used, and clinical rules developed, to address missing functionality. Conclusions: Our test revealed widely varying functionality and appeared to be highly discriminative. Basic clinical decision support was partly absent in two CPOEs. Hospital pharmacists did not rate all test items as important and tried to accommodate the lacking functionality by performing additional checks and developing clinical rules.

Consensus report on therapeutic drug monitoring of mycophenolic acid in solid organ transplantation (Article)

2010-03-15T00:00:00Z

With the increasing use of mycophenolic acid (MPA) in solid organ transplantation, the need for more accurate drug dosing has become evident. Personalized immunosuppressive therapy requires better strategies for avoidance of drug-related toxicity while maintaining efficacy. Few studies have assessed the clinical usefulness of therapeutic drug monitoring (TDM) of MPA in solid organ transplantation in a prospective way, and they have produced opposing results. To provide clinicians with an objective and balanced clinical interpretation of the current scientific evidence on TDM of MPA, a consensus meeting involving 47 experts from around the world was commissioned by The Transplantation Society and held in Rome on November 20 to 21, 2008. The goal of this consensus meeting was to offer information to transplant practitioners on clinically relevant pharmacokinetic characteristics of MPA, to rationalize the basis for currently advised target exposure ranges for MPA in various types of organ transplantation, and to summarize available methods for application of MPA TDM in clinical practice. Although this consensus report does not evaluate the final role of MPA TDM in transplantation, it seeks to examine the current scientific evidence for concentration-controlled dosing of MPA. Copyright

Renal transplant patients at high risk of acute rejection benefit from adequate exposure to mycophenolic acid (Article)

2010-03-01T00:00:00Z

Background: To better define subpopulations in which achieving adequate mycophenolic acid (MPA) concentrations quickly would be important, a post hoc exploratory analysis on the fixed-dose concentration-controlled database was performed, comparing high-versus low-risk renal transplant patients. Methods: Renal transplant patients were treated with mycophenolate mofetil, corticosteroids, and cyclosporine A or tacrolimus. Patients were defined as "high risk" if they had one or more of the following characteristics: delayed graft function, second or third transplantation, panel reactive antibodies >15%, four or more human leukocyte antigen mismatches, or were of black race. Results: A total of 549 patients (61%) were classified as high risk, of whom 284 were on cyclosporine A treatment and 265 on tacrolimus. In high-risk patients, the difference in rejection incidence was 14.3% in the MPA-area under the concentration (AUC) less than 30 mg hr/L vs. 7.8% in the MPA-AUC more than or equal to 30 mg hr/L groups (P=0.025) during the first month after transplantation; whereas, in low-risk patients, there were similar rejection rates (5.7% vs. 4.5%). In the subgroup of high-risk tacrolimus-treated patients, the difference in acute rejection incidence in the first month between patients with MPA-AUC0-12 less than or more than or equal to 30 mg hr/L was most pronounced: 16 of 67 patients (23.9%) vs. 18 of 173 patients (10.4%); P=0.012. Conclusions: The incidence of acute rejection is higher in high-risk patients if MPA-AUC0-12 is below 30 mg hr/L. In contrast, a difference in acute rejection incidence in low-risk patients with MPA-AUC0-12 less than or more than or equal to 30 mg hr/L was not observed. This supports the use of a higher mycophenolate mofetil starting dose in selected patient populations early after transplantation. Copyright

Pharmacokinetics of intravenous immunoglobulin and outcome in Guillain-Barré syndrome (Article)

2009-12-01T00:00:00Z

Objective: Intravenous immunoglobulin (IVIg) is the first choice treatment for Guillain-Barré syndrome (GBS). All patients initially receive the same arbitrary dose of 2g per kg body weight. Not all patients, however, show a good recovery after this standard dose. IVIg clearance may depend on disease severity and vary between individuals, implying that this dose is suboptimal for some patients. In this study, we determined whether the pharmacokinetics of IVIg is related to outcome in GBS. Methods: We included 174 GBS patients who had previously participated in 2 randomized clinical trials. At entry, all patients were unable to walk unaided and received a standard dose of IVIg. Total IgG levels in serum samples obtained immediately before and 2 weeks after the start of IVIg administration were determined by turbidimetry and related to clinical outcome at 6 months. Results: The increase in serum IgG (ΔIgG) 2 weeks after IVIg treatment varied considerably between patients (mean, 7.8g/L; standard deviation, 5.6g/L). Patients with a low ΔIgG recovered significantly more slowly, and fewer reached the ability to walk unaided at 6 months (log-rank p < 0.001). In multivariate analysis adjusted for other known prognostic factors, a low ΔIgG was independently associated with poor outcome ( p = 0.022). Interpretation: After a standard dose of IVIg treatment, GBS patients show a large variation in pharmacokinetics, which is related to clinical outcome. This may indicate that patients with a small increase in serum IgG level may benefit from a higher dosage or second course of IVIg.

Pharmacokinetic role of protein binding of mycophenolic acid and its glucuronide metabolite in renal transplant recipients (Article)

2009-12-01T00:00:00Z

Mycophenolic acid (MPA), the active compound of mycophenolate mofetil (MMF), is used to prevent graft rejection in renal transplant recipients. MPA is glucuronidated to the metabolite MPAG, which exhibits enterohepatic recirculation (EHC). MPA binds for 97% and MPAG binds for 82% to plasma proteins. Low plasma albumin concentrations, impaired renal function and coadministration of cyclosporine have been reported to be associated with increased clearance of MPA. The aim of the study was to develop a population pharmacokinetic model describing the relationship between MMF dose and total MPA (tMPA), unbound MPA (fMPA), total MPAG (tMPAG) and unbound MPAG (fMPAG). In this model the correlation between pharmacokinetic parameters and renal function, plasma albumin concentrations and cotreatment with cyclosporine was quantified. tMPA, fMPA, tMPAG and fMPAG concentration-time profiles of renal transplant recipients cotreated with cyclosporine (n = 48) and tacrolimus (n = 45) were analyzed using NONMEM. A 2- and 1-compartment model were used to describe the pharmacokinetics of fMPA and fMPAG. The central compartments of fMPA and fMPAG were connected with an albumin compartment allowing competitive binding (bMPA and bMPAG). tMPA and tMPAG were modeled as the sum of the bound and unbound concentrations. EHC was modeled by transport of fMPAG to a separate gallbladder compartment. This transport was decreased in case of cyclosporine cotreatment (P < 0.001). In the model, clearance of fMPAG decreased when creatinine clearance (CrCL) was reduced (P < 0.001), and albumin concentration was correlated with the maximum number of binding sites available for MPA and MPAG (P < 0.001). In patients with impaired renal function cotreated with cyclosporine the model adequately described that increasing fMPAG concentrations decreased tMPA AUC due to displacement of MPA from its binding sites. The accumulated MPAG could also be reconverted to MPA by the EHC, which caused increased tMPA AUC in patients cotreated with tacrolimus. Changes in CrCL had hardly any effect on fMPA exposure. A decrease in plasma albumin concentration from 0.6 to 0.4 mmol/l resulted in ca. 38% reduction of tMPA AUC, whereas no reduction in fMPA AUC was seen. In conclusion, a pharmacokinetic model has been developed which describes the relationship between dose and both total and free MPA exposure. The model adequately describes the influence of renal function, plasma albumin and cyclosporine co-medication on MPA exposure. Changes in protein binding due to altered renal function or plasma albumin concentrations influence tMPA exposure, whereas fMPA exposure is hardly affected.

Time-dependent drug-drug interaction alerts in care provider order entry: software may inhibit medication error reductions (Article)

2009-11-01T00:00:00Z

Time-dependent drug-drug interactions (TDDIs) are drug combinations that result in a decreased drug effect due to coadministration of a second drug. Such interactions can be prevented by separately administering the drugs. This study attempted to reduce drug administration errors due to overridden TDDIs in a care provider order entry (CPOE) system. In four periods divided over two studies, logged TDDIs were investigated by reviewing the time intervals prescribed in the CPOE and recorded on the patient chart. The first study showed significant drug administration error reduction from 56.4 to 36.2% (p<0.05), whereas the second study was not successful (46.7 and 45.2%; p>0.05). Despite interventions, drug administration errors still occurred in more than one third of cases and prescribing errors in 79-87%. Probably the low alert specificity, the unclear alert information content, and the inability of the software to support safe and efficient TDDI alert handling all diminished correct prescribing, and consequently, insufficiently reduced drug administration errors.

The CYP2D6 4 polymorphism affects breast cancer survival in tamoxifen users (Article)

2009-11-01T00:00:00Z

Cytochrome P450 2D6 (CYP2D6) plays an important role in the formation of endoxifen, the active metabolite of tamoxifen. In this study the association between the most prevalent CYP2D6 null-allele in Caucasians (CYP2D64) and breast cancer mortality was examined among all incident users of tamoxifen in a population-based cohort study. Breast cancer mortality was significantly increased in patients with the 4/4 genotype (HR = 4.1, CI 95% 1.1-15.9, P = 0.041) compared to wild type patients. The breast cancer mortality increased with a hazard ratio of 2.0 (CI 95% 1.1-3.4, P = 0.015) with each additional variant allele. No increased risk of all-cause mortality or all-cancer mortality was found in tamoxifen users carrying a CYP2D64 allele. The risk of breast cancer mortality is increased in tamoxifen users with decreased CYP2D6 activity, consistent with the model in which endoxifen formation is dependent on CYP2D6 activity.

Inosine monophosphate dehydrogenase messenger RNA expression is correlated to clinical outcomes in mycophenolate mofetil-treated kidney transplant patients, whereas inosine monophosphate dehydrogenase activity is not (Article)

2009-10-01T00:00:00Z

Measurement of the pharmacodynamic biomarker inosine monophosphate dehydrogenase (IMPDH) activity in renal transplant recipients has been proposed to reflect the biological effect better than using pharmacokinetic parameters to monitor mycophenolate mofetil therapy. The IMPDH assays are however labor intensive and this complicates implementation into patient care. Quantification of IMPDH messenger RNA (mRNA) could form an attractive alternative. This study was designed to correlate IMPDH mRNA levels with IMPDH activity and clinical outcome in renal transplant recipients. From a cohort of 101 renal transplant patients, blood samples were drawn pre transplantation and at 4 times after transplantation. IMPDH activity, IMPDH type 1 and type 2 mRNA levels, and mycophenolic acid concentrations were measured and correlated to clinical outcomes. No correlation was found between IMPDH type 1 and type 2 mRNA levels and IMPDH activity in pre- and posttransplant samples. A significant increase in IMPDH mRNA levels was found between day 6 and day 140 after transplantation. IMPDH type 1 and type 2 mRNA levels before transplant showed a trend toward statistically significant higher levels in patients with an acute rejection (P = 0.052 and P = 0.058). After transplant, the IMPDH type 1 and type 2 mRNA levels were significantly lower in patients with an acute rejection (P = 0.026 and P = 0.007). We conclude that IMPDH mRNA levels do not correlate with IMPDH activity but are nevertheless correlated with acute rejections. Furthermore, although the regulation of the expression of the 2 isoforms is presumed to be different, in this study, the changes in the expression of type 1 mRNA closely paralleled those of type 2.

Limited sampling strategies drawn within 3 hours postdose poorly predict mycophenolic acid area-under-the-curve after enteric-coated mycophenolate sodium (Article)

2009-10-01T00:00:00Z

Previous studies predicted that limited sampling strategies (LSS) for estimation of mycophenolic acid (MPA) area-under-the-curve (AUC0-12) after ingestion of enteric-coated mycophenolate sodium (EC-MPS) using a clinically feasible sampling scheme may have poor predictive performance. Failure of LSS was thought to be due to the slow absorption of MPA causing late and variable times of maximum MPA concentration and variable predose concentrations. The aim of this study was to formally test the performance of LSS by developing and validating LSS for estimation of MPA AUC0-12 after EC-MPS administration. Pharmacokinetic data from 109 renal transplant recipients collected during the maintenance period after transplantation were analysed retrospectively. LSS were developed separately for renal transplant patients who concurrently used cyclosporine (n = 79) and for patients not concurrently treated with cyclosporine (n = 30). Data were split into an index and a validation data set. For clinical feasibility reasons, a LSS could consist of a maximum of 3 sampling time points with the latest sample drawn 2 hours after drug administration. LSS with the latest sample drawn 3 hours after drug administration or even later were also tested. The validation of the developed LSS showed that MPA AUC0-12 for patients concurrently treated with cyclosporine was best estimated by AUC0-12 (mg•h•L -1) = 36.536 + 1.642 × C0.5 + 0.569 × C 1.5 + 0.905 × C2 (r2 = 0.33, bias = -1.0 mg•h•L, precision = 24 mg•h•L), whereas AU C0-12[mg•h•L] = 19.801 + 1.827 × C0.5 + 1.111 × C1 + 1.429 × C2 was the best AUC0-12 estimator for patients not cotreated with cyclosporine (r = 0.31, bias = 0.4 mg•h•L, precision = 14.5 mg•h•L). Both LSS showed poor precision and overestimation of AUC0-12 values below the therapeutic window and underestimation of AUC0-12 values above the therapeutic window of MPA. Using C3 as latest sampling time point improved the fit slightly, but not satisfactory, with r still <0.40 and precision still >14.0 mg•h•L. Estimation of MPA AUC0-12 with LSS for EC-MPS drawn within 2 or 3 hours postdose in renal transplant recipients in the maintenance period is likely to result in biased and imprecise results.

A genome-wide association study of acenocoumarol maintenance dosage. (Article)

2009-10-01T00:00:00Z

Several genome-wide association studies have been performed on warfarin. For acenocoumarol, the most frequently used coumarin in many countries worldwide, pharmacodynamic influences are expected to be comparable. Pharmacokinetics however might differ. We aimed to confirm known or identify new genetic variants contributing to interindividual variation on stabilized acenocoumarol dosage by a GWAS. The index population consisted of 1451 Caucasian subjects from the Rotterdam study and results were replicated in 287 subjects from the Rotterdam study extended cohort. Both cohorts were genotyped on the Illumina 550K Human Map SNP array. From polymorphisms tested for association with acenocoumarol dosage, 35 single nucleotide polymorphisms (SNPs) on chromosome 16 and 18 SNPs on chromosome 10 reached genome-wide significance. The SNP with the lowest P-value was rs10871454 on chromosome 16 linked to SNPs within the vitamin K epoxide reductase complex subunit 1 (VKORC1) (P = 2.0 x 10(-123)). The lowest P-value on chromosome 10 was obtained by rs4086116 within cytochrome P450 2C9 (CYP2C9) (P = 3.3 x 10(-24)). After adjustment for these SNPs, the rs2108622 polymorphism within cytochrome P450 4F2 (CYP4F2) gene on chromosome 19 reached genome-wide significance (P = 2.0 x 10(-8)). On chromosome 10, we further identified genetic variation in the cytochrome P450 2C18 (CYP2C18) gene contributing to variance of acenocoumarol dosage. Thus we confirmed earlier findings that acenocoumarol dosage mainly depends on polymorphisms in the VKORC1 and CYP2C9 genes. Besides age, gender, body mass index and target INR, one polymorphism within each of the VKORC1, CYP2C9, CYP4F2 and CYP2C18 genes could explain 48.8% of acenocoumarol dosage variation.

Polymorphisms of the glucocorticoid receptor and avascular necrosis of the femoral heads after treatment with corticosteroids (Article)

2009-10-01T00:00:00Z

A female patient developed avascular necrosis of the femoral heads after receiving low doses of glucocorticosteroids (GC) for 3 months. Genotyping of the GC receptor (GR) showed that she was heterozygous for the Bcl-1 allele and heterozygous for the N363S allele. Interestingly, these GR variants are both associated with higher sensitivity to glucocorticoids. It is not known whether the GR gene polymorphisms are causally related to osteonecrosis. However, the presence of these GR variants, as a combination present in only 1 of the normal Caucasian population, seems suggestive. Studies are warranted to investigate the importance of polymorphisms related to GC sensitivity.

UGT1A9 -275T>A/-2152C>T Polymorphisms Correlate With Low MPA Exposure and Acute Rejection in MMF/Tacrolimus-Treated Kidney Transplant Patients (Article)

2009-09-01T00:00:00Z

Mycophenolate mofetil (MMF) is an immunosuppressive drug commonly used in the context of kidney transplantation. Exposure to the active metabolite mycophenolic acid (MPA) is associated with risk of allograft rejection. MPA pharmacokinetics varies between individuals, the potential cause being the presence of genetic polymorphisms in key enzymes. We genotyped 338 kidney transplant patients for UGT1A8, UGT1A9, UGT2B7, and MRP2 polymorphisms and recorded MPA exposure and biopsy-proven acute rejections (BPARs) during a 1-year follow-up. Tacrolimus-treated patients who were UGT1A9 -275T>A and/or -2152C>T carriers displayed a 20% lower MPA area under the concentration-time curve from 0 to 12 h (AUC0-12) (P = 0.012). UGT1A9*3 carriers displayed a 49% higher MPA AUC0-12 when treated with tacrolimus and a 54% higher MPA AUC0-12 when treated with cyclosporine (P < 0.005). Cyclosporine-treated UGT1A8*2/*2 (518GG) patients had an 18% higher MPA AUC0-12 compared with noncarriers. Carrying the UGT1A9 -275T>A and/or -2152C>T polymorphism significantly predicted acute rejection in fixed-dose (FD) MMF-treated patients receiving tacrolimus (odds ratio 13.3, 95% confidence interval 1.1-162.3; P < 0.05). UGT1A9 -275T>A and/or -2152C>T genotyping may identify patients at risk of MPA underexposure and acute rejection when receiving treatment with MMF and tacrolimus.Clinical Pharmacology & Therapeutics (2009); advance online publication 03 June 2009. doi:10.1038/clpt.2009.83.

Unintended consequences of reducing QT-alert overload in a computerized physician order entry system (Article)

2009-09-01T00:00:00Z

Purpose: After complaints of too many low-specificity drug-drug interaction (DDI) alerts on QT prolongation, the rules for QT alerting in the Dutch national drug database were restricted in 2007 to obviously QT-prolonging drugs. The aim of this virtual study was to investigate whether this adjustment would improve the identification of patients at risk of developing Torsades de Pointes (TdP) due to QT-prolonging drug combinations in a computerized physician order entry system (CPOE) and whether these new rules should be implemented. Methods: During a half-year study period, inpatients with overridden DDI alerts regarding QT prolongation and with an electrocardiogram recorded before and within 1 month of the alert override were included if they did not have a ventricular pacemaker and did not use the low-risk combination cotrimoxazole and tacrolimus. QT-interval prolongation and the risk of developing TdP were calculated for all patients and related to the number of patients for whom a QT-alert would be generated in the new situation with the restricted database. Results: Forty-nine patients (13%) met the inclusion criteria. In this study population, knowledge base-adjustment would reduce the number of alerts by 53%. However, the positive predictive value of QT alerts would not change (31% before and 30% after) and only 47% of the patients at risk of developing TdP would be identified in CPOEs using the adjusted knowledge base. Conclusion: The new rules for QT alerting would result in a poorer identification of patients at risk of developing TdP than the old rules. This is caused by the many non-drug-related risk factors for QT prolongation not being incorporated in CPOE alert generation. The partial contribution of all risk factors should be studied and used to create clinical rules for QT alerting with an acceptable positive predictive value.

Pharmacokinetic modelling of the plasma protein binding of mycophenolic acid in renal transplant recipients (Article)

2009-08-26T00:00:00Z

Background and Objectives: Renal function and the plasma albumin concentration have been shown to correlate with clearance of total mycophenolic acid (MPA). The hypothesis for the underlying mechanism is that low plasma albumin concentrations and accumulation of the glucuronide metabolite of MPA (MPAG) decrease the binding of MPA to albumin. The subsequent increase in the unbound fraction (fu) of MPA (MPAu) produces an increase in total MPA (MPAt) clearance. This study aimed to develop an empirical population pharmacokinetic model to describe the relationships between renal function and albumin concentration and MPAG, MPAuand MPAt, in order to provide insight into the mechanism by which renal function and plasma albumin affect the disposition of MPA. Methods: 774 MPAt, 479 MPAuand 772 total MPAG (MPAGt) plasma concentrations were available from 88 renal transplant recipients on days 11 and 140 after transplantation. Data were analysed using non-linear mixed-effects modelling. Results: Time profiles of MPAuand MPAGtconcentrations were adequately described by two 2-compartment pharmacokinetic models with a link between the central compartments, representing the glucuronidation of MPAuto form MPAG. MPAtconcentrations were modelled using: [MPAt] = [MPAu] + [MPAu]• θpb, with [MPAu] • θpbrepresenting the bound MPA concentration, where [MPAt], [MPAu] and θpbrepresent MPAtconcentration, MPAuconcentration and a factor that correlates to the total number of protein binding places, respectively. According to this equation, fu= [MPAu]/[MPAt] = 1/(1 + θpb) • θpb, and therefore [MPAt], was significantly and independently correlated with creatinine clearance (CLCR), the plasma albumin concentration and the MPAGtconcentration (all p < 0.001). A reduction in CLCRfrom 60 to 25 mL/min correlated with an increase in fufrom 2.7% to 3.5%, accumulation of MPAGtconcentrations from 50 to 150 mg/L correlated with an increase in fufrom 2.8% to 3.7%, and a decrease in plasma albumin concentration from 40 to 30 g/L correlated with an increase in fufrom 2.6% to 3.5%. No significant correlations were detected between MPAuclearance and the plasma albumin concentration or CLCR. Conclusion: The model shows that low CLCR, low plasma albumin concentrations and high MPAG concentrations decrease MPAtexposure by affecting MPA binding to albumin.

Interpatient variability in IMPDH activity in MMF-treated renal transplant patients is correlated with IMPDH type II 3757T>C polymorphism (Article)

2009-08-01T00:00:00Z

OBJECTIVES: The active metabolite of mycophenolate mofetil (MMF), mycophenolic acid, inhibits the activity of the target enzyme inosine monophosphate dehydrogenase (IMPDH). The aim of this study was to correlate eight different single nucleotide polymorphisms of the IMPDH type II gene to the activity of the IMPDH enzyme to explain between-patient differences in IMPDH activity. METHODS AND RESULTS: In a prospective study, we measured IMPDH activity, mycophenolic acid plasma concentrations, and eight polymorphisms of IMPDH type II in de novo kidney transplant recipients, 6 days posttransplantation while on MMF treatment. Polymorphisms in the IMPDH type II gene were only observed for the IMPDH type II 3757T>C (rs11706052) single nucleotide polymorphism. Ten of 101 patients (10%) were heterozygous and two of 101 patients (2%) homozygous for IMPDH type II 3757T>C. The allele frequency was 6.9%. The IMPDH activity over 12h (AUCact) was 49% higher for patients with an IMPDH type II 3757C variant [n=12 vs. n=68; 336 (95% confidence interval: 216-521) vs. 227 (95% confidence interval: 198-260)hμmol/s/mol adenosine monophosphate; P=0.04]. The IMPDH activity measured before transplantation (Actpre-Tx) was not significantly different between IMPDH type II 3757TT wild-type and variant carrier patients (P=0.99). CONCLUSION: We report that the IMPDH type II 3757T>C polymorphism is associated with an increased IMPDH activity in MMF-treated renal transplant patients. This polymorphism explains 8.0% of the interpatient variability in IMPDH activity.

Variation in the CYP2D6 gene is associated with a lower serum sodium concentration in patients on antidepressants (Article)

2009-08-01T00:00:00Z

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • Several antidepressants are metabolized by the polymorphic enzyme cytochrome P450 2D6 (CYP2D6). • The variant allele CYP2D6*4 is the main polymorphism resulting in decreased enzyme activity in Caucasians. • Decreased CYP2D6 enzyme activity potentially leads to higher plasma concentrations of antidepressants. • Consequently, patients carrying the *4 allele are more likely to suffer from adverse drug reactions such as hyponatraemia. WHAT THIS STUDY ADDS • The association between CYP2D6 genotype and serum sodium concentration in users of antidepressants has not been examined thoroughly, and most studies suffer from small numbers of poor metabolizers (PMs) of CYP2D6. • This study shows that serum sodium concentrations in users of tricyclic antidepressive drugs are lower in CYP2D6 PMs than in extensive metabolizers. AIM To study the effect of the CYP2D6*4 polymorphism on serum sodium concentration in users of antidepressants [selective serotonin reuptake inhibitors and tricyclic antidepressants (TCAs)]. METHODS In this population-based cohort study, all subjects in the Rotterdam Study were included who used an antidepressant at baseline and from whom a blood sample was available in which CYP2D6 genotype and serum sodium concentration could be determined (n = 76). Multivariate linear regression was used to study the association between CYP2D6*4 and serum sodium concentration. RESULTS CYP2D6 poor metabolizers (PMs) (*4/*4) had a significantly lower mean serum sodium concentration in comparison with CYP2D6 extensive metabolizers (EMs) (*1/*1) [difference -3.9 mmol l-1; 95% confidence interval (CI) -0.86, -7.03; P = 0.013]. In CYP2D6*4 heterozygotes (*1/*4) serum sodium concentration was 1.7 mmol l-1(95% CI -3.48, 0.18) lower compared with CYP2D6 EMs, but this difference was not statistically significant (P = 0.077). CONCLUSIONS The serum sodium concentration in PMs was lower in users of an antidepressant, especially in TCA users. Therefore CYP2D6 PMs might be at increased risk of developing symptoms of hyponatraemia.

Drug safety alert generation and overriding in a large Dutch university medical centre (Article)

2009-07-01T00:00:00Z

PURPOSE: To evaluate numbers and types of drug safety alerts generated and overridden in a large Dutch university medical centre. METHODS: A disguised observation study lasting 25 days on two internal medicine wards evaluating alert generation and handling of alerts. A retrospective analysis was also performed of all drug safety alerts overridden in the hospital using pharmacy log files over 24 months. RESULTS: In the disguised observation study 34% of the orders generated a drug safety alert of which 91% were overridden. The majority of alerts generated (56%) concerned drug-drug interactions (DDIs) and these were overridden more often (98%) than overdoses (89%) or duplicate orders (80%). All drug safety alerts concerning admission medicines were overridden.Retrospective analysis of pharmacy log files for all wards revealed one override per five prescriptions. Of all overrides, DDIs accounted for 59%, overdoses 24% and duplicate orders 17%. DDI alerts of medium-level seriousness were overridden more often (55%) than low-level (22%) or high-level DDIs (19%). In 36% of DDI overrides, it would have been possible to monitor effects by measuring serum levels. The top 20 of overridden DDIs accounted for 76% of all DDI overrides. CONCLUSIONS: Drug safety alerts were generated in one third of orders and were frequently overridden. Duplicate order alerts more often resulted in order cancellation (20%) than did alerts for overdose (11%) or DDIs (2%). DDIs were most frequently overridden. Only a small number of DDIs caused these overrides. Studies on improvement of alert handling should focus on these frequently-overridden DDIs.

Mycophenolate blood level monitoring: Recent progress: Minireview (Article)

2009-07-01T00:00:00Z

The concentration-effect relationship for mycophenolic acid (MPA), and the high variability in MPA concentrations in patients on standard dose mycophenolate mofetil (MMF) therapy, for some centers has provided enough evidence to implement therapeutic drug monitoring (TDM) for MMF in daily practice. Two randomized trials Adaption de Posologie du MMF en Greffe Renale (APOMYGRE) and fixed-dose versus concentration controlled (FDCC) investigated the added benefit of TDM for MMF in renal transplant recipients. The APOMYGRE study showed a significant reduction in the incidence of acute rejection in concentration-controlled patients, while the FDCC study had a negative outcome, despite a similar study design. Although it was expected that these prospective trials would give the final answer to the question of whether or not TDM for MMF would be of benefit, it seems that the studies have not had much impact on patient management. Several trials have shown the importance of early adequate exposure to MPA in the first week after transplantation. As it will be hard to improve MPA exposure with TDM, this early, ongoing study now investigates the use of an increased starting dose. The increased starting dose will avoid underexposure to MPA in higher proportions of patients shortly after transplantation but may result in more toxicity in patients with MPA exposures exceeding the upper threshold of the therapeutic window.

Association between the CYP2D6*4 polymorphism and depression or anxiety in the elderly (Article)

2009-06-16T00:00:00Z

Introduction: 5-methoxytryptamine (5-MT), a precursor of serotonin, is considered to be an endogeous substrate of cytochrome P450 2D6 (CYP2D6). Homozygous carriers of the variant allele CYP2D6*4 lack CYP2D6 emzyme activity. Relative to extensive metabolizers, these poor metabolizers may have lower baseline serotonin concentrations in various brain regions, and may be more prone to depression or anxity. Aim: To test whether the CYP2D6*4/*4 genotype is associated with a predisposition to depression or anxiety disorders in the elderly. Materials & methods: We conducted a cross-sectional study within the Rotterdam Study, a population-based cohort study, among persons aged 55 years or older, who were screened for depression and anxiety disorder at two consecutive examination rounds. Logistic regression was used to analyze the association between the CYP2D6*4 polymorhism and the risk of depression or anxiety disorders. Results: The risk of major depression in CYP2D*64/*4 was not significantly different from extensive metabolizers (OR = 0.85; 95% Cl: 0.36-2.00; p = 0.72). Neither did we find an association between CYP2D6 genotype and minor depression (OR = 1.56; 95% Cl: 0.69-3.52; p = 0.28). No increased risk of anxiety disorders was found (OR = 1.19; 95% Cl: 0.68-2.09; p = 0.55). Conclusion: Variation in the CYP2D6 gene is not related to a predisposition or anxiety disorders in the elderly.

Improved assay for the nonradioactive determination of inosine 5'-monophosphate dehydrogenase activity in peripheral blood mononuclear cells (Article)

2009-06-01T00:00:00Z

Mycophenolic acid (MPA) inhibits the enzyme inosine 5'-monophosphate dehydrogenase (IMPDH). Thus, the measurement of IMPDH activity could serve as a specific pharmacodynamic (PD) tool for monitoring MPA therapy. At present, however, monitoring of pharmacokinetic parameters is preferred over that of PD parameters because, in general, PD assays are labor-intensive and poorly reproducible. Currently, cell count or protein concentration is widely accepted as methods to normalize enzyme activity. In the present study, we have attempted to further improve a method for the determination of IMPDH activity to increase the robustness and reproducibility of the IMPDH activity assay itself, without making the assay more labor-intensive. Therefore, several aspects of the IMPDH method were investigated regarding their influence on the reproducibility and also modified to increase the feasibility and consistency of the assay. The isolation of peripheral blood mononuclear cells (PBMCs) of whole blood samples was found to be the most variable step. Normalization on cell count is labor-intensive and at the same time has a poor reproducibility. Determination of the protein content in cell extracts is impaired by contamination with extracellular proteins and non-PBMCs. Alternatively, the intracellular substance adenosine monophosphate (AMP) was investigated to normalize the newly generated xanthosine monophosphate. Among various subject groups, no significant differences in mean AMP concentration were found. To simplify the procedure, PBMCs were diluted to a fixed volume after isolation from sample of whole blood, and the IMPDH activity was normalized to the AMP concentration quantified in the same high-performance liquid chromatography run as xanthosine monophosphate was quantified. The within-run and total imprecision (coefficient of variation) ranged from 4.2% to 10.6% and from 6.6% to 11.9%, respectively. In conclusion, the modified method described here for the measurement of IMPDH activity can be used reliably in multicenter trials and in longitudinal studies to evaluate the additional value of any PD monitoring among a diversity of patients treated with MPA. Copyright

Limited sampling strategies for therapeutic drug monitoring of mycophenolate mofetil therapy in patients with autoimmune disease (Article)

2009-06-01T00:00:00Z

Mycophenolate mofetil (MMF) is increasingly used for the treatment of autoimmune diseases (AID). In renal transplant recipients, it has been demonstrated that adjustment of the MMF dose according to the area under the plasma concentration versus time curve (AUC) of mycophenolic acid (MPA), the active moiety of MMF, improves clinical outcome. The aim of this study was to develop a maximum a posteriori Bayesian estimator (MAP-BE) to estimate MPA AUC0-12 in patients with AID using a limited number of samples. The predictive performance of the MAP-BE was compared with a multiple linear regression method. Full MPA concentration versus time curves were available from 38 patients with AID treated with MMF. Nonlinear mixed-effect modeling was used to develop a population pharmacokinetic model. Patients were divided in an index and a validation data set. The pharmacokinetic model derived from the index data set was used to develop several MAP-BEs. The Bayesian estimators were used to predict AUC0-12 in the validation data set on the basis of a limited number of blood samples. The bias and precision of these predictions were compared with those of limited sampling strategies developed with multiple linear regression. The absorption of MPA was described with 2 first-order processes with a short and a long lag time and a subsequent first-order elimination. The 2-compartment model accounted for the enterohepatic recirculation of MPA as well. Using 1-4 samples, MPA AUC0-12 was adequately estimated by the MAP-BE. Bias (-5.5%) was not significantly different from zero, and precision was below 27%. The predictive performance of the multiple linear regression method was comparable. In conclusion, MAP-BEs were developed for the estimation of MPA AUC0-12 in patients with AID. The predictive performance was good and comparable to those of the multiple linear regression method. Due to its flexibility with respect to sample times, the MAP-BE may be preferred over the multiple linear regression method. Copyright

Progressive multifocal leukoencephalopathy, a review and an extended report of five patients with different immune compromised states (Article)

2009-05-01T00:00:00Z

Progressive multifocal leukoencephalopathy (PML) is an opportunistic infection of the brain caused by the JC-virus. Both a decreased cellular or humoral immune response can increase the susceptibility for JC-virus induced PML. Not only HIV infected people are at risk, a wide range of otherwise immune compromised patients are a potential target for this virus. This report of five PML patients shows the importance of a clinician's familiarity with this disease and it's presenting symptoms. The presenting symptoms of PML can sometimes mimic worsening of the underlying disease. Although different therapeutic strategies have been tried, the outcomes remain very poor. In this series, treatment with cidofovir appears not to be effective in treating PML, neither in HIV positive nor HIV negative patients. Experimental therapy with leflunomide, after tapering of the immunosuppressive medication, did change the natural course of PML in one patient.

Long-term survival after kidney transplantation in an HIV-positive patient (Article)

2009-04-17T00:00:00Z

Only a decade ago, human immunodeficiency virus (HIV)-seropositivity was considered an absolute contraindication for organ transplantation. With the currently available experience, it is no longer justified to deny HIV-positive patients access to transplantation. To the best of our knowledge, we here present the longest surviving HIV-positive patient after renal transplantation. The follow-up period after renal transplantation in this HIV-positive female is now 13 yr and she is in good general condition with excellent renal function. Throughout her post-transplant follow-up, we encountered a number of problems that are illustrative of the HIV-positive patient.

Clinical utility of a new enzymatic assay for determination of mycophenolic acid in comparison with an optimized lc-ms/ms method (Article)

2009-04-01T00:00:00Z

The goal of this study was to investigate the clinical utility of a new enzymatic assay for use on COBAS INTEGRA systems (Roche Total MPA assay). From 134 patients, plasma mycophenolic acid (MPA) concentrations were measured with both the enzymatic method and a validated liquid chromatography with tandem mass spectrometry (LC-MS/MS) procedure, to compare these assays. The test principle of the enzymatic assay is inhibition of inosine monophosphate dehydrogenase. Method comparison studies revealed good agreement of results (r > 0.99), overall and in patients with delayed graft function or hypoalbuminemia. MPA area under the concentration-time curve (AUCs) obtained with LC-MS/MS (x) and the enzymatic method (y) compared excellent in patients on cyclosporine (y ≤ 1.04x ĝ̂' 1.05, r ≤ 0.992) or tacrolimus (y ≤ 1.02x ĝ̂' 0.63, r ≤ 0.987). MPA exposure determined with either method at different time points after transplantation agreed well (eg, 25th/50th/75th percentile of day 10 AUCs-LC-MS/MS: 25.8/33.8/45.2 versus enzymatic assay: 26.2/34.4/45.3 mg•h/L). AUCs calculated for both methods were lower at the first 3 time points in patients on cyclosporine compared with tacrolimus (week 4 median cyclosporine/tacrolimus: LC-MS/MS 39.6/56.4 versus enzymatic assay 40.5/56.0 mg•h/L). Both LC-MS/MS and the enzymatic methods revealed a tendency toward lower AUCs and predose levels in patients with biopsy-proven acute rejection (BPAR) (day 10 median: 0.9 mg/L with BPAR and 1.7 mg/L without BPAR). The Roche Total MPA assay is a reliable alternative to LC-MS/MS. It can be applied in the clinical setting allowing for easy, fast, and optimized patient management.

Clinically relevant QTc prolongation due to overridden drug-drug interaction alerts: A retrospective cohort study (Article)

2009-03-01T00:00:00Z

AIMS: To investigate whether, in patients in whom drug-drug interaction (DDI) alerts on QTc prolongation were overridden, the physician had requested an electrocardiogram (ECG), and if these ECGs showed clinically relevant QTc prolongation. METHODS: For all patients with overridden DDI alerts on QTc prolongation during 6 months, data on risk factors for QT prolongation, drug class and ECGs were collected from the medical record. Patients with ventricular pacemakers, patients treated on an outpatient basis, and patients using the low-risk combination of cotrimoxazole and tacrolimus were excluded. The magnitude of the effect on the QTc interval was calculated if ECGs before and after overriding were available. Changes of the QTc interval in these cases were compared with those of a control group using one QTc-prolonging drug. RESULTS: In 33% of all patients with overridden QTc alerts an ECG was recorded within 1 month. ECGs were more often recorded in patients with more risk factors for QTc prolongation and with more QTc overrides. ECGs before and after the QTc override were available in 29% of patients. Thirty-one percent of patients in this group showed clinically relevant QTc prolongation with increased risk of torsades de pointes or ventricular arrhythmias. The average change in QTc interval was +31 ms for cases and -4 ms for controls. CONCLUSIONS: Overriding the high-level DDI alerts on QTc prolongation rarely resulted in the preferred approach to subsequently record an ECG. If ECGs were recorded before and after QTc overrides, clinically relevant QTc prolongation was found in one-third of cases. ECG recording after overriding QTc alerts should be encouraged to prevent adverse events.

Genetic variation in the CYP2D6 gene is associated with a lower heart rate and blood pressure in β-blocker users (Article)

2009-01-01T00:00:00Z

Several β-blockers are metabolized by the polymorphic enzyme cytochrome P450 2D6 (CYP2D6). CYP2D6*4 is the main polymorphism leading to decreased enzyme activity. The clinical significance of impaired elimination of β-blockers is controversial, and most studies suffer from inclusion of small numbers of poor metabolizers (PMs) of CYP2D6. In this study, the association between CYP2D6*4 and blood pressure or heart rate was examined in 1,533 users of β-blockers in the Rotterdam Study, a population-based cohort study. In CYP2D6 *4/*4 PMs, the adjusted heart rate in metoprolol users was 8.5 beats/min lower compared with *1/*1 extensive metabolizers (EMs) (P < 0.001), leading to an increased risk of bradycardia in PMs (odds ratio = 3.86; 95% confidence interval 1.68-8.86; P = 0.0014). The diastolic blood pressure in PMs was 5.4 mm Hg lower in users of β-blockers metabolized by CYP2D6 (P = 0.017) and 4.8 mm Hg lower in metoprolol users (P = 0.045) compared with EMs. PMs are at increased risk of bradycardia.

The effects of guideline implementation for proton pump inhibitor prescription on two pulmonary medicine wards (Article)

2009-01-01T00:00:00Z

Background: It has been demonstrated that 40% of patients admitted to pulmonary medicine wards use proton pump inhibitors (PPIs) without a registered indication. Aim: To assess whether implementation of a guideline for proton pump inhibitor (PPI) prescription on pulmonary medicine wards could lead to a decrease in use and improved appropriateness of prescription. Methods: This prospective study comprised two periods, i.e. the situation before and after guideline implementation. In each period, 300 consecutive patients were included. We registered patient characteristics, medications and occurrence of upper gastrointestinal-related disorders. Results: After implementation, fewer patients were started on PPIs [21% vs. 13%; odds ratio (OR): 0.56; 95% confidence interval (CI): 0.33-0.97] and more users discontinued their use; however, the latter was not significant (3% vs. 6%; OR for continuation: 0.56; 95% CI: 0.14-2.23). Multivariable logistic regression analysis confirmed that PPI use during hospitalization decreased after implementation (adjusted pooled OR: 0.54; 95% CI: 0.32-0.90). Implementation did not result in a change in reported reasons for PPI prescription. There was no significant difference in the occurrence of upper GI-related disorders in the first 3 months after discharge. Conclusions: Guideline implementation for PPI prescription on two pulmonary medicine wards resulted in a reduction in the number of patients starting PPIs during hospitalization, but appropriateness of prescribing PPIs was not affected. Further studies are needed to determine how appropriateness of PPI prescription on pulmonary medicine wards can be further improved.

Population pharmacokinetics of mycophenolic acid: A comparison between enteric-coated mycophenolate sodium and mycophenolate mofetil in renal transplant recipients (Article)

2008-12-01T00:00:00Z

Objective: The pharmacokinetics of mycophenolic acid (MPA) were compared in renal transplant patients receiving either mycophenolate mofetil (MMF) or enteric-coated mycophenolate sodium (EC-MPS). Methods: MPA concentration-time profiles were included from EC-MPS- (n = 208) and MMF-treated (n = 184) patients 4-257 months after renal transplantation. Population pharmacokinetic analysis was performed using nonlinear mixed-effects modelling (NONMEM®). A two-compartment model with first-order absorption and elimination was used to describe the data. Results: No differences were detected in MPA clearance, intercompartmental clearance, or the central or peripheral volume of distribution. Respective values and interindividual variability (IIV) were 16 L/h (39%), 22 L/h (78%), 40 L (100%) and 518 L (490%). EC-MPS was absorbed more slowly than MMF with respective absorption rate constant values of 3.0 h-1 and 4.1 h-1 (p < 0.001) [IIV 187%]. A mixture model was used for the change-point parameter lag-time (tlag) in order to describe IIV in this parameter adequately for EC-MPS. Following the morning dose of EC-MPS, the tlag values were 0.95, 1.88 and 4.83 h for 51%, 32% and 17% of the population (IIV 8%), respectively. The morning tlag following EC-MPS administration was significantly different from both the tlag following MMF administration (0.30 h; p < 0.001 [IIV 11%]) and the tlag following the evening dose of EC-MPS (9.04 h; p < 0.001 [IIV 40%]). Post hoc analysis showed that the tlag was longer and more variable following EC-MPS administration (morning median 2.0 h [0.9-5.5 h], evening median 8.9 h [5.4-12.3 h]) than following MMF administration (median 0.30 h [0.26-0.34 h]; p < 0.001). The morning MPA predose concentrations were higher and more variable following EC-MPS administration than following MMF administration, with respective values of 2.6 mg/L (0.4-24.4 mg/L) and 1.6 mg/L (0.2-7.6 mg/L). The correlation between predose concentrations and the area under the plasma concentration-time curve (AUC) was lower in EC-MPS-treated patients (r2 = 0.02) than in MMF-treated patients (r2 = 0.48). Conclusion: Absorption of MPA was delayed and also slower following EC-MPS administration than following MMF administration. Furthermore, the tlag varied more in EC-MPS-treated patients. MPA predose concentrations were poorly correlated with the MPA AUC in both MMF- and EC-MPS-treated patients.

Therapeutic drug monitoring for mycophenolic acid in patients with autoimmune diseases (Article)

2008-11-01T00:00:00Z

Comparing mycophenolate mofetil regimens for de novo renal transplant recipients: The fixed-dose concentration-controlled trial (Article)

2008-10-27T00:00:00Z

BACKGROUND.: Fixed-dose mycophenolate mofetil (MMF) reduces the incidence of acute rejection after solid organ transplantation. The Fixed-Dose Concentration Controlled trial assessed the feasibility and potential benefit of therapeutic drug monitoring in patients receiving MMF after de novo renal transplant. METHODS.: Patients were randomized to a concentration-controlled (n=452; target exposure 45 mg hr/L) or a fixed-dose (n=449) MMF-containing regimen. The primary endpoint was treatment failure (a composite of biopsy-proven acute rejection [BPAR], graft loss, death, or MMF discontinuation) by 12 months posttransplantation. RESULTS.: Mycophenolic acid (MPA) exposures for both groups were similar at most time points and were below 30 mg hr/L in 37.3% of patients at day 3. There was no difference in the incidence of treatment failure (25.6% vs. 25.7%, P=0.81) or BPAR (14.9% vs. 15.5%, P>0.05) between the concentration-controlled and the fixed-dose groups, respectively. We did find a significant relationship between MPA-area under the concentration-time curve on day 3 and the incidence of BPAR in the first month (P=0.009) or in the first year posttransplantation (P=0.006). For later time points (day 10, month 1) there was no significant relationship between area under the concentration-time curve and BPAR (0.2572 and 0.5588, respectively). CONCLUSIONS.: There was no difference in the incidence of treatment failure between the concentration-controlled and the fixed-dose groups. The applied protocol of MMF dose adjustments based on target MPA exposure was not successful, partly because physicians seemed reluctant to implement substantial dose changes. Current initial MMF doses underexpose more than 35% of patients early after transplantation, increasing the risk for BPAR.

Continuous ambulatory peritoneal dialysis: Pharmacokinetics and clinical outcome of paclitaxel and carboplatin treatment (Article)

2008-10-01T00:00:00Z

Purpose: Administration of chemotherapy in patients with renal failure, treated with hemodialysis or continuous ambulatory peritoneal dialysis (CAPD) is still a challenge and literature data is scarce. Here we present a case study of a patient on CAPD, treated with weekly and three-weekly paclitaxel/ carboplatin for recurrent ovarian cancer. Experimental: During the first, second and ninth cycle of treatment, blood, urine and CAPD samples were collected for pharmacokinetic analysis of paclitaxel and total and unbound carboplatin-derived platinum. Results: Treatment was well tolerated by the patient. No excessive toxicity was observed and at the end of treatment she was in a complete remission. The plasma pharmacokinetics of paclitaxel were unaltered compared to historical data, with neglectable urinary and CAPD clearance. In contrast, the pharmacokinetics of carboplatin were altered, with doubled half-lives compared to patients with normal renal function. Of the administered carboplatin dose, up to 20% was cleared via the dialysate, while only up to 8% was cleared via the urine. Conclusion: Paclitaxel and carboplatin can be safely administered to patients with chronic renal failure on CAPD. For paclitaxel the generally applied dose can be administered, and although for carboplatin dose-adjustment is required due to the diminished renal function, the dose can be calculated using Calvert's formula.

A drug transporter for all ages? ABCB1 and the developmental pharmacogenetics of cyclosporine (Article)

2008-09-01T00:00:00Z

The clinical use of the immunosuppressive agent cyclosporine is complicated by its toxicity, narrow therapeutic window and highly variable pharmacokinetics between individuals. In adults, genetic polymorphisms in the genes encoding the cyclosporine-metabolizing enzymes CYP3A4 and CYP3A5, as well as the ABCB1 gene, which encodes the efflux-pump P-glycoprotein, seem to have a limited effect, if any, on cyclosporine pharmacokinetics. However, the authors have now reported for the first time an association between cyclosporine oral bioavailability and the ABCB1 c.1236C>T and c.2677G>T polymorphisms, as well as the related haplotype c.1199G-c.1236C-c.2677G-c.3435C, in children with end-stage renal disease older than 8 years of age. Carriers of the variant alleles had a cyclosporine oral bioavailability that was around 1.5-times higher compared with noncarriers. This association was not observed in children younger than 8 years of age. In addition, no relation between cyclosporine disposition and genetic variation in the CYP3A4, CYP3A5, ABCC2, SLCO1B1 and NR1I2 genes was observed. These data suggest that the effect of ABCB1 polymorphisms on cyclosporine pharmacokinetics is related to age, and thus developmental stage. Although further study is necessary to establish the predictive value of ABCB1 genotyping for individualization of cyclosporine therapy in children older than 8 years, an important step towards further personalized immunosuppressive drug therapy has been made.

Renal function as a predictor of irinotecan-induced neutropenia (Article)

2008-08-01T00:00:00Z

Although approximately half of the administered dose of irinotecan is recovered in urine, scarce data are available on the association of renal function with irinotecan pharmacokinetics and toxicity. Here, these relationships are investigated in 187 patients treated with irinotecan in a three-weekly schedule. No significant effects on irinotecan pharmacokinetics were found in these patients. However, in 131 patients treated with the registered dose, categorized renal function was related to hematological toxicity. The incidence of grade 3-4 neutropenia decreased as function of creatinine clearance, particularly in nonsmoking patients (P < 0.01). Patients with slower creatinine clearance (35-66 ml/min) had a four-times higher risk of grade 3-4 neutropenia (58% vs. 14%; P < 0.001). This study suggests that pretreatment renal function values are associated with irinotecan-induced neutropenia. A confirmatory analysis is warranted to determine whether measures of renal function should be incorporated in future attempts toward individualized treatment with irinotecan.

Turning Off Frequently Overridden Drug Alerts: Limited Opportunities for Doing It Safely (Article)

2008-07-01T00:00:00Z

Objectives: This study sought to identify opportunities to safely turn off frequently overridden drug-drug interaction alerts (DDIs) in computerized physician order entry (CPOE). Design: Quantitative retrospective analysis of drug safety alerts overridden during 1 month and qualitative interviews with 24 respondents (18 physicians and 6 pharmacists) about turning off frequently overridden DDI alerts, based on the Dutch drug database, in a hospital setting. Screen shots and complete texts of frequently overridden DDIs were presented to physicians of internal medicine, cardiology, and surgery and to hospital pharmacists who were asked whether these could be turned off hospital-wide without impairing patient safety, and the reasons for their recommendations. Results: Data on the frequency of alerts overridden in 1 month identified 3,089 overrides, of which 1,963 were DDIs. The category DDIs showed 86 different alerts, of which 24 frequently overridden alerts, accounting for 72% of all DDI overrides, were selected for further evaluation. The 24 respondents together made 576 assessments. Upon investigation, differences in the reasons for turning off alerts were found across medical specialties and among respondents within a specialty. Frequently mentioned reasons for turning off were "alert well known," "alert not serious," or "alert not needing (additional) action," or that the effects of the combination were monitored or intended. For none of the alerts did all respondents agree that it could be safely turned off hospital-wide. The highest agreement was 13 of 24 respondents (54%). A positive correlation was found between the number of alerts overridden and the number of clinicians recommending to turn them off. Conclusion: Although the Dutch drug database is already a selected reduction from all DDIs mentioned in literature, the majority of respondents wanted to turn off DDI alerts to reduce alert overload. Turning off DDI alerts hospital-wide appeared to be problematic because of differences among physicians regarding drug-related knowledge and of differences across the hospital in routine drug monitoring practices. Furthermore, several reasons for suppression of alerts could be questioned from a safety perspective. Further research should investigate when each of the following might help: changes in alert texts; new differential alert triggers based on clinician knowledge or specialty; and nonintrusive alert presentation so long as serum levels and patient parameters are measured and stay within limits.

Association of graded allele-specific changes in CYP2D6 function with imipramine dose requirement in a large group of depressed patients (Article)

2008-06-01T00:00:00Z

The inactivation and clearance of the tricyclic antidepressant imipramine is dependent on CYP2D6 activity. First, CYP2C19 converts imipramine into the active metabolite desipramine, which is then inactivated by CYP2D6. This retrospective single center study aimed to prove whether CYP2C19 and ample CYP2D6 genotyping (taking into consideration four null alleles and three decreased-activity alleles) could be used to predict imipramine and desipramine plasma concentrations in depressed patients, and whether genotype-based drug dose recommendations might assist in the early management of imipramine pharmacotherapy. In 181 subjects with major depressive disorder, drug doses were recorded, imipramine and desipramine plasma concentrations were monitored and CYP2C19 (*2) and CYP2D6 genotype (*3, *4, *5, *6, *9, *10, *41 and gene duplication) were obtained, yielding graded allele-specific CYP2D6 patient groups. Desipramine and imipramine+desipramine plasma concentration per drug dose unit, imipramine dose at steady state, and imipramine dose requirement significantly depended on CYP2D6 genotype (Kruskal-Wallis test, P<0.0001). Mean (±s.d.) drug dose requirements were 131 (±109), 155 (±70), 217 (±95), 245 (±125), 326 (±213), and 509 (±292) mg imipramine/day in carriers of 0, 0.5, 1, 1.5, 2, and >2 active CYP2D6 genes, respectively. Our protocol for CYP2D6 genotyping will thus importantly aid in the prediction of imipramine metabolism, allowing for the use of an adjusted starting dose and faster achievement of predefined imipramine+desipramine plasma levels in all genetic patient subgroups. Therefore, therapeutic efficacy and efficiency may be improved, the number of adverse drug reactions decreased, and hospital stay reduced.

Influence of the CYP2D6*4 polymorphism on dose, switching and discontinuation of antidepressants (Article)

2008-04-01T00:00:00Z

Aims: To study the effect of CYP2D6*4 on antidepressant dose, switching and discontinuation of therapy. Methods: The study consisted of all subjects in the Rotterdam Study, who received a first antidepressant prescription between April 1st 1991 and July 1st 2005 and for whom data on CYP2D6 genotype were available. Binary logistic regression was performed to study the association between CYP2D6*4 and switching to any other antidepressant or discontinuation of therapy within 45 days. The difference in mean antidepressant dose was compared between CYP2D6 genotypes using t-tests and repeated measurements analyses. Results: In users of tricyclic antidepressants (TCAs) the risk of switching to another antidepressant was significantly higher in poor metabolizers (PMs:*4/*4) compared with extensive metabolizers (EMs:*1/*1), with an adjusted OR of 5.77 (95% CI 1.59, 21.03; P = 0.01). In SSRI users there was no significant difference (OR 0.91; 95% CI 0.20, 4.15; P = 0.90). Heterozygous patients did not have an increased risk of switching in both TCA and SSRI users. The mean TCA dose was significantly lower in PMs than in EMs at the third and fourth prescription (difference 0.11 DDD, P = 0.03). In SSRI users the difference in mean dose between PMs and EMs was significant at the third prescription (0.17 DDD; P = 0.02). Conclusions: The risk of switching to another antidepressant in TCA users is higher in PMs than in EMs. The maintenance doses of antidepressants were significantly lower in PMs. However, the question whether genotyping prior to the start of antidepressant therapy contributes substantially to the optimization of pharmacotherapy, requires further study.

CYP3A5 genotype is not associated with a higher risk of acute rejection in tacrolimus-treated renal transplant recipients (Article)

2008-04-01T00:00:00Z

OBJECTIVE: Patients expressing the tacrolimus-metabolizing enzyme, cytochrome P450 (CYP) 3A5, require more tacrolimus to reach target concentrations. We studied the influence of the CYP3A5*3 allele, which results in the absence of CYP3A5 protein, on tacrolimus dose and exposure, as well as the incidence of biopsy-proven acute rejection (BPAR) after renal transplantation. METHODS: A total of 136 patients participating in a prospective, randomized-controlled clinical trial with the primary aim of comparing the efficacy of a fixed-dose versus a concentration-controlled mycophenolate mofetil immunosuppressive regimen, were genotyped for CYP3A5*3. The patients described herein, participated in a pharmacogenetic substudy and were all treated with mycophenolate mofetil, corticosteroids and tacrolimus. Tacrolimus predose concentrations (C0) were measured on day 3 and 10, and month 1, 3, 6 and 12. RESULTS: Compared with CYP3A5*3/*3 individuals (n=110), patients carrying at least one CYP3A5*1 (wild-type) allele (CYP3A5 expressers; n=26) had a lower tacrolimus C0 on day 3 only (16.6 versus 12.3 ng/ml, respectively), whereas dose-corrected tacrolimus C0 were significantly lower in the latter group at all time points. After day 3, the overall daily tacrolimus dose was 68% higher in CYP3A5 expressers (P<0.001). The incidence of BPAR was comparable between CYP3A5 expressers and nonexpressers (8 versus 16%, respectively; P=0.36). CONCLUSION: We conclude that patients expressing CYP3A5 need more tacrolimus to reach target concentrations and have a lower tacrolimus exposure shortly after transplantation. This delay in reaching target concentrations, however, did not result in an increased incidence of early BPAR and therefore, genotyping for CYP3A5 is unlikely to improve short-term transplantation outcome.

Plasma concentrations of mycophenolic acid acyl glucuronide are not associated with diarrhea in renal transplant recipients (Article)

2007-07-01T00:00:00Z

The aim of this study was to determine whether plasma concentrations of the acyl (AcMPAG) and phenolic (MPAG) glucuronide metabolites of mycophenolic acid (MPA) were related to diarrhoea in renal transplant patients on mycophenolate mofetil (MMF) with cyclosporine (CsA) or tacrolimus (TCL). Blood samples (0, 30, 120 min) were taken at days 3, 10, week 4, months 3, 6 and 12 for determination of MPA, MPAG and AcMPAG. MPA-AUC was estimated using validated algorithms. Two hour AUCs were calculated for MPAG and AcMPAG. Immunosuppressive therapy consisted of CsA/MMF (n = 110) and of TCL/MMF (n = 180). In 70/290 (24%) patients 86 episodes of diarrhoea were recorded during 12 months. Significantly more patients on TCL (31.1%) suffered from diarrhea compared to CsA (12.7%). MMF dose, MPA-AUC and the 2 h AUCs of MPAG and AcMPAG did not differ between patients with and without diarrhoea. Plasma AcMPAG and MPAG concentrations were substantially higher in patients on CsA compared with TCL, while MPA-AUC was lower in the former group. These data support the concept that CsA inhibits the biliary excretion of MPAG and AcMPAG, thereby potentially reducing the risk of intestinal injury through enterohepatic recycling of MPA and its metabolites.

Pharmacokinetics of mycophenolate mofetil in hematopoietic stem cell transplant recipients (Article)

2007-06-01T00:00:00Z

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is increasingly used in the prophylaxis of graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation (HCT). Few pharmacokinetic data are available about the use of MMF for this indication. This case series aimed at analyzing the pharmacokinetics of MMF in a population of HCT recipients representative for everyday practice. From 15 HCT recipients, serial plasma samples were taken after twice-daily oral intake of MMF. Plasma concentrations of total MPA and its glucuronide metabolites, as well as free MPA, were quantified. Median apparent oral MPA clearance (CL/F), apparent half-life, and total MPA area under the curve for hours 0 to 12 (AUC0-12, normalized to 1000 mg MMF) were, respectively, 56 L/h (range: 29-98 L/h), 2.3 hours (range: 0.8-5.7 hours), and 18.0 mg*h/L (range: 10-35 mg*h/L). Total MPA concentrations were below 2 mg/L 8 hours after MMF administration, indicating reduced enterohepatic recirculation. Median free MPA AUC0-12 (normalized to 1000 mg MMF) was 224 μg*h/L (range: 56-411 μg*h/L). Because of high CL/F, total MPA exposure in HCT recipients is low and apparent half-life is short in comparison with reference values from renal transplantation. Exposure may be improved in HCT recipients by higher or more frequent MMF dosing.

Time-dependent clearance of mycophenolic acid in renal transplant recipients (Article)

2007-06-01T00:00:00Z

Aims: Pharmacokinetic studies of the immunosuppressive compound mycophenolic acid (MPA) have shown a structural decrease in clearance (CL) over time after renal transplantation. The aim of this study was to characterize the time-dependent CL of MPA by means of a population pharmacokinetic meta-analysis, and to test whether it can be described by covariate effects. Methods: One thousand eight hundred and ninety-four MPA concentration-time profiles from 468 renal transplant patients (range 1-9 profiles per patient) were analyzed retrospectively by nonlinear mixed effect modelling. Sampling occasions ranged from day 1-10 years after transplantation. Results: The pharmacokinetics of MPA were described by a two-compartment model with time-lagged first order absorption, and a first-order term for time-dependent CL. The model predicted the mean CL to decrease from 35 l h-1(CV = 44%) in the first week after transplantation to 17 l h-1(CV = 38%) after 6 months. In a covariate model without a term for time-dependent CL, changes during the first 6 months after transplantation in creatinine clearance from 19 to 71 ml min-1, in albumin concentration from 35 to 40 g l-1, in haemoglobin from 9.7 to 12 g dl-1and in cyclosporin predose concentration from 225 to 100 ng ml-1corresponded with a decrease of CL from 32 to 19 l h-1. Creatinine clearance, albumin concentration, haemoglobin and cyclosporin predose concentration explained, respectively, 19%, 12%, 4% and 3% of the within-patient variability in MPA CL. Conclusions: By monitoring creatinine clearance, albumin concentration, haemoglobin and cyclosporin predose concentration, changes in MPA exposure over time can be predicted. Such information can be used to optimize therapy with mycophenolate mofetil.

Therapeutic drug monitoring of mycophenolic acid: Does it improve patient outcome? (Article)

2007-04-01T00:00:00Z

Treatment with the immunosuppressive agent mycophenolate mofetil (MMF) decreases the risk of rejection after renal transplantation and improves graft survival compared with azathioprine. The exposure to the active metabolite mycophenolic acid (MPA) is correlated to the risk of developing acute rejection. The interpatient variability in exposure of MPA is wide relative to the proposed therapeutic window of the MPA AUC0-12(30 - 60 mg.h/l). The pharmacokinetics of MPA are influenced by patient characteristics such as gender, time after transplantation, serum albumin concentration, renal function, comedication and pharmacogenetic factors. Therapeutic drug monitoring is likely to reduce inter-patient variability. Limited sampling strategies are used to predict the full AUC0-12. Three prospective randomised studies compared concentration controlled MMF therapy to a fixed-dose regimen. Preliminary outcomes of these studies showed conflicting results and longer follow up is needed to further clarify the role of therapeutic drug monitoring in increasing the therapeutic potential of MMF.

Yersinia pseudotuberculosis bacteraemia in a kidney transplant patient (Article)

2002-01-01T00:00:00Z

Withdrawal of cyclosporine or prednisone six months after kidney transplantation in patients on triple drug therapy: a randomized, prospective, multicenter study (Article)

2002-01-01T00:00:00Z

Uncertainty exists regarding the necessity of continuing triple therapy consisting of mycophenolate mofetil (MMF), cyclosporine (CsA), and prednisone (Pred) after kidney transplantation (RTx). At 6 mo after RTx, 212 patients were randomized to stop CsA (n = 63), stop Pred (n = 76), or continue triple drug therapy (n = 73). The MMF dose was 1000 mg twice daily, target CsA trough levels were 150 ng/ml, and Pred dose was 0.10 mg/kg per d. Follow-up was until 24 mo after RTx. Biopsy-proven acute rejection occurred in 14 (22%) of 63 patients after CsA withdrawal compared with 3 (4%) of 76 in the Pred withdrawal group (P = 0.001) and 1 (1.4%) of 73 in the control group (P = 0.0001). Biopsy-proven chronic rejection was present in one patient in the control group, in nine patients after CsA withdrawal (P = 0.006 versus control group); and in four patients after discontinuation of Pred (NS). Graft loss occurred in two versus one patient after CsA or Pred withdrawal, respectively, and in two patients in the control group (NS). Patients who successfully withdrew CsA had a significantly lower serum creatinine during follow-up. Pred withdrawal resulted in a reduction in mean arterial pressure, and the total cholesterol/HDL ratio increased. In conclusion, rapid CsA withdrawal at 6 mo after RTx results in a significantly increased incidence of biopsy-proven acute and chronic rejection. Pred withdrawal was safe and resulted in a reduction in mean arterial pressure. However, patient and graft survival and renal function 2 yr after RTx were not different among groups.

Impact of intraoperative donor management on short-term renal function after laparoscopic donor nephrectomy (Article)

2002-01-01T00:00:00Z

OBJECTIVE: To determine whether intraoperative diuresis, postoperative recovery, and early graft function differ between laparoscopic open nephrectomy (LDN) and open donor nephrectomy (ODN). SUMMARY BACKGROUND DATA: Laparoscopic donor nephrectomy can reduce donor complications in terms of decreased pain and shorter convalescence. Although its technical feasibility has been established, concerns have been raised about the impaired renal function resulting from pneumoperitoneum and short- and long-term function of kidneys removed by LDN. METHODS: Between December 1997 and December 2000, 89 LDNs were performed at the authors' institution. These were compared with 83 conventional ODNs performed between January 1994 and December 1997. Graft function, intraoperative variables, and clinical outcome were compared. RESULTS: Laparoscopic donor nephrectomy was attempted in 89 patients and completed in 91% (81/89). Length of hospital stay was significantly shorter in the laparoscopic group. During kidney dissection, the amount of fluids administered and intraoperative diuresis were significantly lower for LDN. In recipients, mean serum creatinine was higher after LDN compared with ODN 1 day after surgery. From postoperative days 2 until 28, there were no differences in serum creatinine. Graft survival rates were similar for LDN and ODN. CONCLUSIONS: Donors can benefit from an improvement in postoperative recovery after LDN. Assessment of an adequate perioperative hydration protocol is mandatory to ensure optimal kidney quality during laparoscopic procurement. The initial graft survival and function rates justify continued development and adoption of LDN.

Mycophenolic acid plasma concentrations in kidney allograft recipients with or without cyclosporin: a cross-sectional study (Article)

1999-01-01T00:00:00Z

BACKGROUND: Combining cyclosporin (CsA) and prednisone with mycophenolate mofetil (MMF) results in a significant reduction in the rate of biopsy-proven acute rejection after kidney transplantation. This is achieved with a standard daily MMF dosage of 2 or 3 g. Whether monitoring of the pharmacologically active metabolite mycophenolic acid (MPA) will lead to improved safety and efficacy is unclear. METHODS: We monitored MPA trough levels in 18 kidney transplant recipients treated with CsA, prednisone, and MMF (63 samples) and in 11 patients (31 samples) treated with prednisone and MMF only, in a cross-sectional study. All patients were at least 3 months after transplantation with stable graft function. All patients were treated with 2 g MMF for at least 3 months and 10 mg prednisone. RESULTS: The MPA trough levels in the CsA-treated patients were significantly lower (P<0.0001; Mann-Whitney) than those in patients on MMF and prednisone only (mean MPA levels 1.98+/-0.12 vs 4.38+/-0.40 mg/l respectively). CONCLUSIONS: Although all patients were treated with an identical MMF dose, a significant difference was found in the MPA trough levels between CsA- vs non-CsA-treated patients. This suggests that CsA influences the MPA trough level. The level at which CsA affects the MPA trough levels is unclear.

Effect of mycophenolate mofetil on erythropoiesis in stable renal transplant patients is correlated with mycophenolic acid trough levels (Article)

1999-01-01T00:00:00Z

BACKGROUND: Both mycophenolate mofetil (MMF) and azathioprine (AZA) are immunosuppressive drugs that inhibit purine synthesis. In theory, MMF selectively inhibits lymphocyte proliferation, while AZA has well-known effects on red blood cells and thrombocytes as well. In renal transplant recipients we replaced CsA therapy by MMF in an attempt to reduce the immunosuppressive load 1 year after kidney transplantation. During this study we observed the effect of MMF on haematological parameters such as haemoglobin (Hb), leukocytes, and thrombocytes. METHODS: One year after kidney transplantation 26 stable patients were converted from cyclosporin A (CsA) to MMF (2 g/day). Thereafter, these patients were tapered twice in their MMF dose from 2 g to 1.5 g (4 months after conversion) and from 1.5 to 1 g (8 months after conversion) per day. The Hb levels, leukocyte and thrombocyte counts, and mycophenolic acid (MPA) trough levels were routinely measured. RESULTS: After conversion from CsA to MMF not only creatinine levels and the number of leukocytes, but also the haemoglobin (Hb) level significantly decreased in 21/26 patients (P=0.0004). In eight patients the Hb level dropped more than 1 mmol/l (=1.61 g/dl). Only in two of eight patients was an explanation for blood loss found. The effect on Hb level did not ameliorate after the first MMF dose reduction to 1.5 g/day. After tapering the MMF dose to 1 g/day, the Hb approached the pre-conversion level. Not only the MMF dose but also the mycophenolic acid (MPA) trough level correlated with the Hb level. CONCLUSIONS: After conversion from CsA to MMF 1 year after kidney transplantation, a decrease in Hb level and leukocyte count was observed. The MPA trough level correlated also with the Hb level. The effect on the Hb level was reversible after dose reduction. This finding suggests that MMF exerts a negative effect on erythropoietic cells.

Renal insufficiency after heart transplantation: a case-control study (Article)

1998-01-01T00:00:00Z

BACKGROUND: In Rotterdam 304 heart transplants have been performed since 1984. End-stage renal failure, necessitating renal replacement therapy, has developed in 24 patients (8%) after an interval of 25-121 months (median 79 months). After starting renal replacement therapy one-year survival was only 60%. Overall survival after heart transplantation, however, was favourable: 5 and 10 year survival rates of 79% and 50% respectively. METHODS: A case-control study was performed to identify possible risk factors in cases who went on to develop end-stage renal failure compared to controls. RESULTS: We found that renal failure was not limited to elderly patients with ischaemic heart disease, but also occurred in young patients having dilated cardiomyopathy. A significant rise in the serum creatinine was found in cases compared to controls as early as 3 months after transplantation. Cyclosporin dose and trough levels were not different between cases and controls. Neither were there differences in the use of calcium-antagonists or other antihypertensive drugs, allopurinol or diuretics. Rejection incidence was also similar between the two groups. CONCLUSIONS: Renal failure after heart transplantation is a long term complication of cyclosporin use that is not limited to elderly patients with ischaemic heart disease. Cyclosporin dose and trough levels in the cases were not different from patients maintaining stable good renal function, indicating that cyclosporin nephrotoxicity is the result of an individually determined susceptibility to cyclosporin. Suggestions for future strategies to prevent renal failure are given.

Cytomegalovirus colitis in a CMV-seropositive renal transplant recipient on triple drug therapy (including mycophenolate) (Article)

1997-01-01T00:00:00Z

The role of anti Interleukin-2 Receptor monoclonal antibody (8T563) in the prevention of acute rejection after organ transplantation (Doctoral Thesis)

1996-05-15T00:00:00Z