Impact of early cyclosporin average blood concentration on early kidney transplant failure

Limited sampling strategies for estimating intravenous and oral cyclosporine area under the curve in pediatric hematopoietic stem cell transplantation

BACKGROUND

The optimal monitoring strategy for cyclosporine (CsA) in pediatric hematopoietic stem cell transplantation (HSCT) patients remains unclear. Although there is a growing interest in the use of the area under the concentration-time curve (AUC), measurement of AUC in clinical settings is often impractical. The objective of this study was to identify and validate limited sampling strategies (LSSs) for the prediction of CsA AUC after intravenous (IV) and oral (PO) administration in this population.

METHODS

Sixty-eight pediatric patients who underwent HSCT and received CsA were investigated. Twelve-hour pharmacokinetic profiles (n = 138) performed per standard of care were collected. Weighted multiple linear regression was used to investigate all possible LSSs consisting of 4 or less concentration-time points. Their predictive performance was evaluated by leave one out cross validation and external validation by measuring the root mean squared relative error (RMSE%) and the 95th percentile of the absolute relative error (AE%). Values less than 20% were considered clinically acceptable.

RESULTS

Nine LSSs (4 IV and 5 PO) convenient for clinical application proved to have clinically acceptable performance. Notably, LSS based on C0, C2, and C4 was found to be accurate for estimation of CsA exposure after both IV and PO administration with the 95th percentile of AE% of 19.7% and 17.5%, respectively.

CONCLUSIONS

LSSs using 3 or 4 concentration-time points obtained within 4 hours postdose provide a convenient and reliable method to estimate CsA exposure in this population. These LSSs may facilitate future research aiming at better defining the relationship between AUC and clinical outcomes.

Impact of sampling time deviations on the prediction of the area under the curve using regression limited sampling strategies

The regression limited sampling strategy approach (R-LSS), which is based on a small number of blood samples drawn at selected time points, has been used as an alternative method for the estimation of the area under the concentration-time curve (AUC). However, deviations from planned sampling times may affect the performance of R-LSS, influencing related therapeutic decisions and outcomes. The aim of this study was to investigate the impact of different sampling time deviation (STD) scenarios on the estimation of AUC by the R-LSS using a simulation approach. Three types of scenarios were considered going from the simplest case of fixed deviations, to random deviations and then to a more realistic case where deviations of mixed nature can occur. In addition, the sensitivity of the R-LSS to STD in each involved sampling point was evaluated. A significant impact of STD on the performance of R-LSS was demonstrated. The tolerance of R-LSS to STD was found to depend not only on the number of sampling points but more importantly on the duration of the sampling process. Sensitivity analysis showed that sampling points at which rapid concentration changes occur were relatively more critical for AUC prediction by R-LSS. As a practical approach, nomograms were proposed, where the expected predictive performance of R-LSS was provided as a function of STD information. The investigation of STD impact on the predictive performance of R-LSS is a critical element and should be routinely performed to guide R-LSS selection and use.

Increased incidence of early de novo cancer in liver graft recipients treated with cyclosporine: an association with C2 monitoring and recipient age

The goal of this study was to determine the risk factors for de novo cancer after liver transplantation (LTx). Retrospective analyses were performed in 385 LTx patients who underwent transplantation between 1986 and 2007. In total, 50 (13.0%) recipients developed de novo malignancy. The cumulative incidence of de novo cancer at 1, 5, 10, and 15 years after LTx was 2.9% +/- 0.9%, 10.5% +/- 1.8%, 19.4% +/- 3.0%, and 33.6% +/- 6.8%, respectively. The standardized incidence ratio of malignancy in LTx patients compared to the general population was 2.2 (95% confidence interval: 1.6-2.8). After excluding posttransplant lymphoproliferative disorder and skin cancer, patients with de novo cancer had a significantly lower survival rate compared to recipients who remained cancer-free. The identified univariate risk factors for de novo cancer were cyclosporine A (CsA) treatment, time period of LTx, and recipient age. In multivariate analysis, only CsA treatment emerged as an independent risk factor for de novo cancer, which was attributed to more aggressive cancer types. A surprising finding was that CsA treatment specifically enhanced cancer risk in patients who underwent transplantation after 2004, when C(2) monitoring (blood concentration at 2 hours postdose) was introduced. In addition, these patients showed a significantly lower acute rejection rate, which might reflect a more robust immunosuppressive status caused by the CsA-C(2) regimen. When age was considered, only patients < or =50 years had a higher cancer rate when treated with CsA compared to treatment with tacrolimus. Our data suggest that, compared to tacrolimus treatment, CsA treatment with C(2) monitoring or in younger patients of < or =50 years is associated with a higher early de novo cancer risk after LTx.

Population pharmacokinetics and bayesian estimator of cyclosporine in pediatric renal transplant patients

Cyclosporine A (CsA) is an immunosuppressive drug widely used in pediatric renal graft recipients. Its large interindividual pharmacokinetic variability and narrow therapeutic index render therapeutic drug monitoring necessary. However, information about CsA pharmacokinetics is scarce and no population pharmacokinetic (popPK) studies in these populations have been reported so far. to the objectives of this study were 1) to develop a PKpop model and identify the individual factors influencing the variability of CsA pharmacokinetics in pediatric kidney recipients; and 2) to build a Bayesian estimator allowing the estimation of the main PK parameters and exposure indices to CsA on the basis of a limited sampling strategy (LSS). The popPK analysis was performed using the NONMEM program. A total of 256 PK profiles of CsA collected in 98 pediatric renal transplant patients (mean age 9.7 +/- 4.5 years old) within the first year posttransplantation were studied. A 2-compartment model with first-order elimination, and Erlang distribution to describe the absorption phase, fitted the data adequately. For Bayesian estimation, the best LSS was determined based on its performance in estimating area under the concentration-time curve (AUC0-12h) and validated in an independent group of 20 patients. The popPK analysis identified body weight and posttransplant delay as individual factors influencing the apparent central volume of distribution and the apparent clearance, respectively. Bayesian estimation allowed accurate prediction of AUC0-12h using predose, C1h, and C3h blood samples with a mean bias between observed and estimated AUC of 0.5% +/- 11% and good precision (root mean square error = 10.9%). This article reports the first popPK study of CsA in pediatric renal transplant patients. It confirms the reliability and feasibility of CsA AUC estimation in this population. The body weight and the posttransplantation delay were identified to influence PK interindividual variability of CsA and were included in the Bayesian estimator developed, which could be helpful in further clinical trials.

Impact of cyclosporine in the development of immunosuppressive therapy

Cyclosporine has been of great interest to the transplant community during the last 20 years. It has permitted an evolution of knowledge through the changes in its original galenic formulation of Sandimmune to Neoral, and now through the recent application of the knowledge of pharmacodynamics and pharmacokinetics to tailor drug doses to each individual. The achievements of cyclosporine are still valid and possibly will be for the next years.

Therapeutic monitoring of cyclosporine in kidney transplantation: the Halifax experience

Appropriate dosing of an immunosuppressive agent is critical to its efficacy and tolerability. Finding a simple and effective method of monitoring cyclosporine (CsA/CyA) has been formidable despite a long history of widespread usage. Earlier reports linked CsA dosing to trough levels (C0), whereas later more elaborate systems have evaluated efficacy linked to 12-hour area-under-the-curve (AUC(0-12)) as a measure of total drug exposure. Recent work done at our center and elsewhere has shown that the 2-hour postdose concentration (C2) to be simple and more effective than the C0 or the AUC. With C2 monitoring as a guide to CsA dosing, acute rejection (AR) and nephrotoxicity (NT) can be effectively reduced. Furthermore, absorption profile as per C2 levels further emphasizes the importance of achieving the targeted peak concentration in the first week of transplantation. The C2 concentration strategy is discussed in light of newer induction agents and other immunosuppression.

Use of cyclosporine in renal transplantation

Since 1983, cyclosporine has been the backbone of immunosuppression in clinical organ transplantation. Cyclosporine is usually used in combination with steroids and with another second-line immunosuppressant like azathioprine or mycofenolate mofetil. With these regimens, graft survival at 1 year exceeds 90% and long-term results are excellent. The main complication is renal toxicity, which is usually secondary to excessive exposure. The new microemulsion formulation of cyclosporine, introduced in recent years, has improved intestinal absorption and bioavailability and resulted in much less intrapatient variation than the older formulation. The introduction of 2-hour peak blood level monitoring, which corresponds closely to the area under the curve of the drug, allows more appropriate dosing, thus minimizing rejection owing to underexposure or toxicity owing to overexposure. As new effective immunosuppressants are currently becoming available for use in combination with cyclosporine, the transplant community can look forward to more effective and safer immunosuppression.

Therapeutic drug monitoring of cyclosporine: 20 years of progress

Since its introduction 20 years ago, cyclosporine (CyA), a powerful immunosuppressant with a narrow therapeutic window, remains the cornerstone of many drug regimens in renal transplantation. However, attempts to balance its therapeutic value with its pleiotropic side effects continue to challenge clinicians. To address the wide intraindividual and interindividual differences in absorption, distribution, metabolism, and elimination of the oil-based formulation of CyA (Sandimmune), a microemulsion (Neoral) was introduced; it displayed better absorption and lower intraindividual variability. Neoral also improves the utility of therapeutic monitoring of CyA to estimate exposure to the drug and predict patient outcomes. Drug monitoring techniques are undergoing continual refinement: today, a limited sampling strategy--C2 monitoring--shows great promise as a comparatively simple, safe, and effective method to optimize patient outcomes during both short-term and maintenance CyA therapy. However, it is not clear whether this method is useful for treatment optimization with generic formulations of CyA. Although generic substitutes meet federal bioequivalence criteria, they may not display the same pharmacokinetic properties. Further, preliminary data have shown a 10% lower 1-year graft survival rate among patients treated with generic versus Neoral CyA. Current challenges in optimizing CyA therapy include determining pretransplant patient characteristics relevant to selection of the appropriate exposure or the development of a Bayesian forecasting technique that predicts dose adjustments necessary to achieve the optimal drug regimen during the critical period immediately posttransplant.

Can a pharmacokinetic approach to immunosuppression eliminate ethnic disparities in renal allograft outcome?

Although renal allograft outcome correlates more closely with area under the concentration time curve (AUC) for cyclosporin (CsA) compared with the 12-h trough level (C0), few studies have prospectively evaluated pharmacokinetic monitoring in kidney transplantation. This paper describes a study designed to evaluate the impact of a novel approach to CsA-based immunosuppression on ethnic differences in renal allograft outcome. Sixty (32 African Americans and 28 Caucasians) renal transplant recipients were treated with cyclosporin-based triple therapy. Morning and evening doses were independently adjusted to reach an AUC0-12 of 6600-7200 ng h/mL and a C0 of 250-325 ng/mL, respectively. AUCs were measured within 48 h of starting CsA, and as often as necessary to maintain target levels. Only two patients experienced significant adverse events related to immunosuppression. One (Caucasian) developed haemolytic uremic syndrome and was converted to tacrolimus, while another (African American) developed acute vascular rejection. One graft was lost (Caucasian) due to death with a functioning graft. An average of 8 AUCs (range 5-13) were measured in the first 3 months. AUCs were significantly higher in African Americans compared with Caucasians only in the first and second month. C0 values were similar in both groups throughout the study period. A pharmacokinetic approach to immunosuppression allows individualization of CsA exposure, and appears to reduce ethnic disparities in renal allograft outcome.

Modifications in cyclosporine (CsA) microemulsion blood concentrations by olestra

OBJECTIVE

Determine whether olestra alters the absorption of cyclosporine microemulsion in pediatric renal transplant recipients.

DESIGN

Prospective, open-label, crossover pharmacokinetic study.

SETTING

General clinical research center in a university medical setting providing tertiary care.

PARTICIPANTS

Seven pediatric-adolescent renal transplant recipients, ages 9 to 18, 5 to 24 months post-transplant with mean serum creatinine of 0.9 mg/dL (range, 0.7-1.6 mg/dL).

METHODOLOGY

Patients participated in 2 study periods: 1. Patients were given their usual dose of Neoral (Novartis Pharmaceuticals Corporation, East Hanover, NJ) without olestra, 2. patients were given their usual dose of Neoral combined with 0.35 g/kg (maximum of 16 g of olestra or approximately 2 ounces of Lays WOW [Frito Lay, Plano, TX] potato chips). The 2 study periods were separated by a minimum 7-day washout period. CsA blood concentrations were obtained at 1, 2, 3, 4, 6, 8, and 12 hours after drug administration.

RESULTS

Each patient in the study had a consistent decrease in area under the curve (AUC) when given olestra along with their usual dose of Neoral, compared with giving Neoral alone (5,018 ng*hr/mL versus 4,086 ng*hr/mL; P <.001). There also was a decrease in maximum concentration (Cmax) when Neoral was given with olestra compared with giving Neoral alone (1,202 ng/mL versus 876 ng/mL; P =.015). There was no statistical difference in the mean elimination rate or the trough values for both regimens (half-life 4.767 hours versus 4.771 hours and trough levels of 143 ng/mL versus 124 ng/mL).

CONCLUSION

Olestra decreases total CsA exposure in pediatric renal transplant recipients. The noted decrease in AUC was not adequately predicted by CsA trough values which could lead to rejection episodes in the clinical setting.

Therapeutic drug monitoring of immunosuppressant drugs in clinical practice

BACKGROUND

Therapeutic drug monitoring (TDM) is essential to maintain the efficacy of many immunosuppressant drugs while minimizing their toxicity. TDM has become more refined with the development of new monitoring techniques and more specific assays.

OBJECTIVE

This article summarizes current data on TDM of the following immunosuppressant drugs used in organ transplantation: cyclosporine, tacrolimus, sirolimus, everolimus, and mycophenolate mofetil.

METHODS

Published data were identified by a MEDLINE search of the English-language literature through March 2001 using the terms therapeutic drug monitoring, cyclosporine, tacrolimus, sirolimus, everolimus, and mycophenolate mofetil. Relevant conference abstracts were also included.

RESULTS

TDM of cyclosporine has been well studied, and recent findings indicate that monitoring of drug levels 2 hours after dosing is a more sensitive predictor of outcome than trough (C0) monitoring. C0 levels are being used more widely in TDM of tacrolimus; however, the relationship between C0 and area under the curve has varied widely in clinical trials, with correlations ranging from 0.11 to 0.92. The use of TDM of sirolimus, everolimus, and mycophenolate mofetil is evolving rapidly.

CONCLUSIONS

TDM of immunosuppressant drugs that have a narrow therapeutic index is an increasingly useful tool for minimizing drug toxicity while maximizing prevention of graft loss and organ rejection.

Randomized, international study of cyclosporine microemulsion absorption profiling in renal transplantation with basiliximab immunoprophylaxis

Increasing information suggests that absorption profiling may be superior to trough level monitoring for optimal concentration control of cyclosporine microemulsion (Neoral) therapy, and that CsA exposure early post-transplant may correlate significantly with reduced risk of acute graft rejection. This randomized, prospective, multicenter international concentration-controlled study was conducted in 21 renal transplant centers in 8 countries to test and compare the clinical feasibility, functionality, accuracy, precision and prediction of rejection by cyclosporine microemulsion absorption profiling to conventional trough-level drug monitoring. Primary or second renal allograft recipients treated with basiliximab, cyclosporine microemulsion and prednisone immunosuppression were randomized to two study groups in which cyclosporine microemulsion therapy was monitored using a multipointalgorithm or by trough levels. The two study arms were comparable in terms of baseline characteristics, treatment and clinical outcomes. Treatment failure, consisting of acute rejection, graft loss or death, occurred with equal incidence in the two groups (30% and 33%, respectively). Diagnostic feasibility, measured as the proportion of samples obtained within the designated time window, was marginally lower in area under the time-concentration curve (AUC) than in trough groups, but the therapeutic accuracy and precision were comparable or superior in the AUC group. Cox regression analysis performed across study groups showed a highly significant correlation between the predicted probability of acute rejection and cyclosporine (CsA) exposure measured by AUC over the entire 12-h dosage interval (AUC[0-12]) (p = 0.0068), AUC over the first 4 h of the 12-h dosage interval (AUC[0-4]) (p = 0.0014) or 2h post-dose (C2) CsA level (p = 0.0027). Day 3 dose- and weight-corrected C2 values (EMIT equivalent) separated patients into low (< 200 microg/L/mg/kg dose), intermediate (200-350 microg/L/mg/kg dose) and high absorber categories (> 350 microg/L/mg/kg dose), defining those at greatest risk. Within these categories, C2 values above approximately 1500 microg/L by day 3 post-transplant were associated with the lowest predicted probability of rejection. Comparable analysis by Cox regression using C0 levels did notreach statistical significance. Absorption profiling is a feasible, accurate and precise method for monitoring cyclosporine microemulsion therapy in clinical practice and, as shown in the companion article, may be simplified by the use of single-point C2 concentrations which accurately predict individual AUC[0-4] exposure levels. Both cyclosporine microemulsion relative absorption (i.e. dose- and weight-corrected exposure) and CsA exposure (measured by predicted AUC or C2 levels) are closely correlated with the risk of rejection, and define patients at high and low risk of acute graft rejection. Trough (C0) levels are not closely correlated with either CsA exposure or rejection risk, and should not be considered reliable for monitoring cyclosporine microemulsion therapy.

Cyclosporine microemulsion (Neoral) absorption profiling and sparse-sample predictors during the first 3 months after renal transplantation

Recent data suggest that optimal cyclosporine (CsA) exposure early post-transplant significantly reduces the risk of acute graft rejection. They indicate that trough level monitoring is inadequate for precise concentration-controlled therapy, and suggest that absorption profiling may offer a superior approach for guiding clinical immunosuppression with Neoral. An international, prospective, multicenter study examined the feasibility, accuracy, precision and clinical utility of cyclosporine microemulsion (Neoral) absorption profiling in de novo renal transplant recipients receiving basiliximab immunoprophylaxis and cyclosporine microemulsion maintenance immunosuppression. The nested pharmacokinetic study reported here was conducted in 4 study centers in which full (11-point) pharmacokinetic profiles were performed on days 3, 7, 14 and 84 post-transplant to examine absorption profile and absorption efficiency, and to determine optimal sparse-sampling pharmacokinetic methods to predict Neoral exposure. Twenty-four patients had complete 12-h pharmacokinetic (PK) data on all 4 sampling days. Area under the time-concentration curve (AUC) over the first 4 h of the 12-h dosage interval (AUC[0-4]) and AUC over the entire 12-h dosage interval (AUC[0-12]) reached 3803 +/- 1033 and 7462 +/- 2120 microg.h/L respectively, by day 3, remained stable throughout the first 2 weeks, and declined to 2310 +/- 698 and 4062 +/- 1158 microg.h/L by day 84 (p < 0.001). AUC[0-4], capturing the drug absorption phase, represented 52% of the AUC[0-12] values across the four PK study days (mean R2 > 0.90). Between-patient variability was highest for C0 and C1 (mean coefficient of variation [c.v.] 36-47%), and lower for C2 (mean c.v. 28%) and subsequent time-points during the dosing interval. Mean relative CsA absorption, measured by dose- and weight-adjusted AUC[0-4] and AUC[0-12], increased significantly over time. The dose- and weight-corrected AUC[0-4h] (DWC.AUC[0-4]) rose by over 100% (p < 0.001) from 753 +/- 202 at day 3 to 905 +/- 232 at day 7, 1080 +/- 330 at day 14 and 1521 +/- 316 by day 84, while the dose-and weight-corrected AUC[0-12h] (DWC.AUC[0-12]) rose by over 80% (p < 0.001) from 1477 +/- 390 microg.h/L/ mg/kg on day 3, to 1721 +/- 426 on day 7, 2086 +/- 478 on day 14 and 2690 +/- 602 on day 84 (p < 0.001). Relative CsA absorption varied over 5-fold between patients at day 3, but patients tended to remain within the same quartiles over time. Sparse-sample modeling identified optimum 3-point, 2-point and 1-point predictors for AUC[0-4] and AUC[0-12]. C2 was the most accurate and robust .1-point predictor for AUC[0-4] (mean R2: 0.80), while C3 was superior for AUC[0-12] (mean R2: 0.75). C0 was not a good predictor of either AUC[0-4] or AUC[0-12] (mean R2: 0.13 and 0.24, respectively).

CONCLUSION

Absorption profiling defines the heterogeneity in CsA exposure and relative absorption post-transplant. A 2-h post-dose blood sample is the most consistent, accurate and robust single-point predictor of the absorption phase measured by AUC[0-4] and should replace trough level monitoring for accurate concentration-control of Neoral therapy in the clinical setting. The use of additional samples at 1 and 3h is more complex and costly, but increases prediction accuracy and may be valuable in selected patients with erratic absorption.

Absorption profiling of cyclosporine microemulsion (neoral) during the first 2 weeks after renal transplantation

BACKGROUND

Evidence suggests that optimal immunosuppressive drug exposure must be achieved early posttransplant to minimize the risk of acute graft rejection. This study was designed to examine the absorption profile of Neoral during the first 2 weeks after renal transplantation, to develop simple sparse-sampling pharmacokinetic methods to predict exposure, and to explore the target range for optimal clinical immunosuppression under conditions of normal clinical practice.

METHODS

The prospective multicenter study was conducted in six Canadian renal transplant centers in patients receiving Neoral-based immunosuppression. Full (8-point) pharmacokinetic studies were performed on days 3, 7, and 14 posttransplant in a nested subset of patients, and the occurrence and severity of acute rejection, infection or other adverse effects, routine laboratory parameters, and vital signs were assessed on days 3, 7, 14, and 28.

RESULTS

A total of 38 adult kidney graft recipients were studied, of whom a nested subset of 16 patients had complete 12-hr pharmacokinetic (PK) data on all 3 sampling days. Mean area under the time-concentration curve over the entire 12-hr dosage interval (AUC[0-12]) was 9249+/-3236 microg.hr/L by day 3 and did not change significantly throughout the study, although dose-corrected AUC[0-12] rose by 20% from 1924+/-671 microg.hr/L on day 3 to 2316+/-697 microg.hr/L on day 14 (P=0.067). Mean AUC[0-4] was 4566+/-1463 microg.hr/L by day 3 and also did not change significantly, although the dose-adjusted AUC[0-4] rose by 31% from 952+/-317 microg.hr/L on day 3 to 1250+/-697 microg.hr/L on day 14 (P=0.009). AUC[0-4] represented 52% of the AUC[0-12] values across the three PK study days and closely predicted this latter value (R2=0.803 day 3, R2=0.972 day 14). Cyclosporine (CsA) concentration profiles became more uniform throughout the first 14 days posttransplant, with a reduction in Tmax from 2.45 to 1.48 hr (P<0.005) and a significant decrease in coefficient of variation for AUC[0-12] (35% vs. 21%, P<0.005) and for Tmax (47.4% vs. 33.1%, P<0.005). Predosage trough level (C0) was a poor predictor of drug exposure, with R2 values less than 0.5 for AUC[0-4] and 0.7 for AUC[0-12] at all time points. Sparse sample modeling identified three 3-point sparse-sampling strategies that predicted AUC[0-12] and AUC[0-4] with R2 values approaching or exceeding 0.9 on all three study days; C2 or C3 seemed to be the most important single predictor, with R2 values > 0.80. Ten of the 36 treated patients (27.8%) experienced 13 episodes of acute rejection by 28 days posttransplant. Longitudinal logistic regression showed no association between C0 and rejection, but lower AUC[0-12] values were marginally (P=0.099) and lower AUC[0-4] values were significantly (P=0.046) associated with increased risk of rejection. CsA exposure on day 7 (n=29) was significantly lower in patients who experienced acute rejection in the second week than in those who were rejection free whether measured by AUC[0-12] (7976+/-1476 vs. 10,239+/-2759 microg.hr/L; P=0.048), AUC[0-4] (4027+/-412 vs. 5623+/-1389 microg.hr/L; P<0.0001), C2 (1116+/-183 vs. 1852+/-522 microg/L; P<0.0001), or Cmax (1415+/-323 vs. 2084+/-450 microg/L; P=0.005), and rejection was significantly less common in patients with an AUC[0-4]> 4,500 microg.hr/L (7% vs. 40%; P=0.041) or a C2 level>1500 microg/L (0% vs. 58%; P<0.001) on day 7 (sensitivity, 100%; specificity, 75%; positive predictive value, 58%; negative predictive value, 100%). There was no evident relationship between CsA exposure and renal toxicity within this patient sample.

CONCLUSIONS

Absorption of CsA is highly heterogeneous immediately posttransplant, although the pharmacokinetic profile normalizes, interpatient variability decreases, and CsA absorption increases throughout the first 2 weeks permitting a reduction in Neoral dose to achieve constant exposure. Trough (C0) levels do not accurately predict CsA exposure or rejection risk and should be replaced by sparse or single point (C2) sampling methods, which offer a high predictive value to optimize the use of this drug and reduce rejection risk. Acute rejection is significantly more common with low CsA exposure during the first week posttransplant, and levels above the threshold of approximately AUC[0-4] 4500 microg.hr/L or C2 1500 microg/L are desirable to minimize the risk of rejection.

2,500 living donor kidney transplants: a single-center experience

OBJECTIVE

To review a single center's experience and outcome with living donor transplants.

SUMMARY BACKGROUND DATA

Outcome after living donor transplants is better than after cadaver donor transplants. Since the inception of the authors' program, they have performed 2,540 living donor transplants. For the most recent cohort of recipients, improvements in patient care and immunosuppressive protocols have improved outcome. In this review, the authors analyzed outcome in relation to protocol.

METHODS

The authors studied patient and graft survival by decade. For those transplanted in the 1990s, the impact of immunosuppressive protocol, donor source, diabetes, and preemptive transplantation was analyzed. The incidence of rejection, posttransplant steroid-related complications, and return to work was determined. Finally, multivariate analysis was used to study risk factors for worse 1-year graft survival and, for those with graft function at 1 year, to study risk factors for worse long-term survival.

RESULTS

For each decade since 1960, outcome has improved after living donor transplants. Compared with patients transplanted in the 1960s, those transplanted in the 1990s have better 8-year actuarial patient and graft survival rates. Death with function and chronic rejection have continued to be a major cause of graft loss, whereas acute rejection has become a rare cause of graft loss. Cardiovascular deaths have become a more predominant cause of patient death; infection has decreased. Donor source (e.g., ideally HLA-identical sibling) continues to be important. For living donor transplants, rejection and graft survival rates are related to donor source. The authors show that patients who had preemptive transplants or less than 1 year of dialysis have better 5-year graft survival and more frequently return to full-time employment. Readmission and complications remain problems; of patients transplanted in the 1990s, only 36% never required readmission. Similarly, steroid-related complications remain common. The authors' multivariate analysis shows that the major risk factor for worse 1-year graft survival was delayed graft function. For recipients with 1-year graft survival, risk factors for worse long-term outcome were pretransplant smoking, pretransplant peripheral vascular disease, pretransplant dialysis for more than 1 year, one or more acute rejection episodes, and donor age older than 55.

CONCLUSIONS

These data show that the outcome of living donor transplants has continued to improve. However, for living donors, donor source affects outcome. The authors also identify other major risk factors affecting both short- and long-term outcome.

Limited sampling strategies for estimating cyclosporin area under the concentration-time curve: review of current algorithms

Cyclosporin, the drug of first choice in transplantation surgery, is characterized by a low therapeutic index and variable absorption, so close monitoring of the drug is required to optimize the dosing. Predose blood cyclosporin levels are measured routinely for therapeutic monitoring, but this approach is not optimal because the area under the concentration-time curve (AUC) correlates better with clinical events. However, conventional methods of measuring AUC require many blood samples, which is not viable in a routine clinical setting. AUC monitoring can be simplified for use in a clinical setting by using a limited sampling strategy (LSS) that allows AUC to be estimated using a small number of blood samples collected at specific times. This article reviews the current literature on estimating cyclosporin AUC using LSS. Thirty-eight papers suggesting the use of specific time points were found. LSS has been developed for different transplant types, with different dosing regimens, and with different assays. Most authors suggested either two- or three-sample equations. Results from authors who validated their models suggest that equations defined on one transplant type may be applicable to other transplant types, to both adults and children, and to early or late after transplantation. Moreover, it seems that there is flexibility in the choice of equations available to clinicians. The number of samples to collect for accurate estimations is a matter of debate, but a wise choice can minimize the number. The choice of the optimal LSS and validation are discussed.