Therapeutic Drug Monitoring Of Cyclosporine Research Articles

A Robust Procedure for Determination of Immunosuppressants Cyclosporine A and Tacrolimus in Blood Samples with Detection of LC–MS/MS

The immunosuppressants monitoring is crucial in the treatment of transplant patients to avoid the risk of organ rejection. So it is vital to develop an accurate method to obtain precise and reliable results. Herein, a liquid chromatography tandem mass spectrometry (LC–MS/MS) based method was developed and validated, which could simultaneously realize the accurate quantification of cyclosporine A and tacrolimus with a total run time of 4.5 min. Unlike the previously described methods, the highlight of this assay is that there is no using zinc sulfate in the protein precipitation of the whole blood sample, which can effectively prolong the lifespan of mass spectrometry. In addition, the linearity, matrix effect, carryover, accuracy, intraday and interday precision of this method were investigated. The linear range of tacrolimus and cyclosporine were 1–40 ng/mL and 50–2000 ng/mL, respectively; The correlation coefficients (R2) were both greater than 0.995. The intraday and interday precision of cyclosporine and tacrolimus were ≤ 10%. The lower limit of quantitation (LLOQ) of tacrolimus and cyclosporine A were 1 ng/mL and 50 ng/mL, respectively. The main features of this method are good accuracy, sensitivity, specificity, rapidness, robustness and high throughput. It is suitable for therapeutic drug monitoring of cyclosporine A and tacrolimus in routine clinical diagnostics.

Medical Management of Canine Chronic Ulcerative Stomatitis Using Cyclosporine and Metronidazole.

Canine chronic ulcerative stomatitis (CCUS) is a spontaneously occurring, painful, and often debilitating condition of the oral cavity, with a suspected immune-mediated component. The response to pharmacological treatment is generally poor, thus the need to identify more effective medical therapies for this condition. This article describes a prospective clinical trial that was designed to evaluate the efficiency of a combination of cyclosporine and metronidazole in managing CCUS. The hypothesis was that a combination of cyclosporine and metronidazole would effectively minimize clinical signs associated with CCUS. Ten client-owned dogs with a biopsy-confirmed diagnosis consistent with CCUS were prescribed cyclosporine (5 mg/kg) for 1 week, followed by the addition of metronidazole (15-20 mg/kg), both administered orally once daily. The cyclosporine dosage interval was lengthened over time. Dogs were observed for a 6-month period and evaluated using a 32-point Canine Ulcerative Stomatitis Disease Activity Index (CUSDAI). Regular cyclosporine therapeutic drug monitoring was also conducted by the measurement of whole blood cyclosporine levels and the pharmacodynamic assessment of the T-cell expression of IL-2. The results demonstrated that a combination of cyclosporine and metronidazole was effective in minimizing the clinical signs of CCUS and in reducing CUSDAI scores. Neither blood cyclosporine levels nor the T-cell expression of IL-2 predicted improvement in clinical signs and CUSDAI scores, although there was a correlation between blood drug concentrations and the suppression of T-cell IL-2 expression. The evaluation of clinical signs and CUSDAI scores appears to be the most effective means of assessing response to therapy, and therapeutic drug level monitoring does not appear to be routinely indicated.

Drug interaction profile of TKI alectinib allows effective and safe treatment of ALK+ lung cancer in the kidney transplant recipient

ALK targeting with tyrosine kinase inhibitors (TKIs) is a highly potent treatment option for the therapy of ALK positive non-small cell lung cancer (NSCLC). However, pharmacokinetics of TKIs leads to clinically significant drug interactions, and the interfering co-medication may hamper the anti-cancer therapeutic management.Here, we present for the first time a drug interaction profile of ALK-TKIs, crizotinib and alectinib, and immunosuppressive agent cyclosporine A in kidney transplant recipients diagnosed with ALK+ lung cancer. Based on therapeutic drug monitoring of cyclosporin A plasma level, the dose of cyclosporine A has been adjusted to achieve a safe and effective therapeutic level in terms of both cancer treatment and kidney transplant condition. Particularly, 15 years upon the kidney transplantation, the stage IV lung cancer patient was treated with the 1st-line chemotherapy, the 2nd-line ALK-TKI crizotinib followed by ALK-TKI alectinib. The successful therapy with ALK-TKIs has been continuing for more than 36 months, including the period when the patient was treated for COVID-19 bilateral pneumonia. Hence, the therapy of ALK+ NSCLC with ALK-TKIs in organ transplant recipients treated with cyclosporine A may be feasible and effective.

Therapeutic Drug Monitoring of Cyclosporine Using Single Sampling Strategy

Cyclosporine is mainly used as Immunosuppressant after different kinds of transplantation including bone marrow, lungs, kidneys, liver, heart, and other types of organ transplantations. Immunosuppressants diminish organ rejection and elongate the survival of the transplanted organs. Due to the narrow therapeutic ranges and significantly
 high interindividual and intraindividual variability in blood levels of cyclosporine, there is essential and vital need of therapeutic drug monitoring (TDM) of this drug in order to maintain the patient within the required therapeutic concentrations, which consequently lead to optimizing the clinical outcome and decrease the hazard of toxicity or rejection following organ transplantations. The current review article was aimed to present data for using a single or possibly two blood sampling strategy to be used for TDM of cyclosporine in order to assess the optimal blood levels of cyclosporine used in organ transplant recipients. The results showed that steady state blood concentration of cyclosporine obtained after 2 hours (C2) and possibly after 3 hours (C3) of drug administration are the best sampling time points which reflect total drug exposure (area under blood concentration versus time curve=AUC) and consequently reflecting the effect and the adverse effect(s) of cyclosporine. On the other hand, blood samples obtained at other time points particularly steady state trough concentration obtained before the next dose (C0) demonstrated poor correlation with total drug exposure and consequently the clinical outcome of the drug. Moreover, this study also demonstrated that for organs transplantations TDM of cyclosporine and assessing the clinical conditions of the patients should be routinely performed in order to adjust the dose to get optimal effect and to diminish the adverse effects of the drug. This review article focused on the findings which indicated that monitoring steady-state blood levels of cyclosporine after 2 hours (C2) and likely after 3 hours (C3) of drug intake may be used as ideal surrogate index in TDM of cyclosporine and for predicting the clinical outcome of the drug in all and different types of organs transplantations.

Therapeutic Drug Monitoring of Cyclosporine Using Single Sampling Strategy

Cyclosporine is mainly used as Immunosuppressant after different kinds of transplantation including bone marrow, lungs, kidneys, liver, heart, and other types of organ transplantations. Immunosuppressants diminish organ rejection and elongate the survival of the transplanted organs. Due to the narrow therapeutic ranges and significantly high interindividual and intraindividual variability in blood levels of cyclosporine, there is essential and vital need of therapeutic drug monitoring (TDM) of this drug in order to maintain the patient within the required therapeutic concentrations, which consequently lead to optimizing the clinical outcome and decrease the hazard of toxicity or rejection following organ transplantations. The current review article was aimed to present data for using a single or possibly two blood sampling strategy to be used for TDM of cyclosporine in order to assess the optimal blood levels of cyclosporine used in organ transplant recipients. The results showed that steady state blood concentration of cyclosporine obtained after 2 hours (C2) and possibly after 3 hours (C3) of drug administration are the best sampling time points which reflect total drug exposure (area under blood concentration versus time curve=AUC) and consequently reflecting the effect and the adverse effect(s) of cyclosporine. On the other hand, blood samples obtained at other time points particularly steady state trough concentration obtained before the next dose (C0) demonstrated poor correlation with total drug exposure and consequently the clinical outcome of the drug. Moreover, this study also demonstrated that for organs transplantations TDM of cyclosporine and assessing the clinical conditions of the patients should be routinely performed in order to adjust the dose to get optimal effect and to diminish the adverse effects of the drug. This review article focused on the findings which indicated that monitoring steady-state blood levels of cyclosporine after 2 hours (C2) and likely after 3 hours (C3) of drug intake may be used as ideal surrogate index in TDM of cyclosporine and for predicting the clinical outcome of the drug in all and different types of organs transplantations.

Therapeutic drug monitoring of cyclosporine and tacrolimus in Myanmar kidney transplant patients

IntroductionRenal transplantation is one of the best options for patients suffering from end stage renal disease (ESRD). Cyclosporine and Tacrolimus are mainly applied in immunosuppressive therapy after transplantation of liver, kidney, heart, and other organs. The used of immunosuppressant drugs improve the survival of transplanted organs and reduce organ rejection. Because of their narrow therapeutic index and significant inter-individual variability in blood concentrations, they need to monitor carefully. Therapeutic drug monitoring of tacrolimus and cyclosporine were needed to optimize the outcome in patients after renal transplantations. Maintaining the drugs levels reduce the risks of toxicity or rejection, respectively. ObjectiveThe aim of this study is to identify the optimum blood trough level for cyclosporine and tacrolimus in Myanmar kidney transplant recipients. Materials and methodA retrospective cross sectional design was used and data collected from 50 patients who underwent kidney transplantation and receiving either cyclosporine or tacrolimus within six months after kidney transplantation. Among them 15 and 35 patients are taking cyclosporine and tacrolimus, respectively. For cyclosporine or tacrolimus trough-level monitoring, whole blood sample was drawn 15 min before the next dose and measured by immunoassay method. ResultsThe results showed that majority of cyclosporine and tacrolimus whole blood levels based on C0 (before the dose) concentration were achieved the therapeutic range. ConclusionTherefore, drugs concentration and the recommended clinical conditions should be routinely monitored to adjust the treatment and reduce adverse reactions. Therapeutic drug monitoring of cyclosporine and Tacrolimus are important for the benefits of renal transplant patients in Myanmar.

Relationship between cyclosporine area-under-the curve and acute graft versus host disease in pediatric patients undergoing hematopoietic stem cell transplant: A prospective, multicenter study

Traditionally in hematopoietic stem cell transplant (HSCT), cyclosporine doses are individualized using cyclosporine trough concentrations (C0) while area under the concentration vs time curve (AUC) is used in solid organ transplant. AUC potentially has an important relationship with the development of acute graft-versus-host-disease (aGVHD). We conducted a prospective study to describe the relationship between severe (grade III-IV) aGVHD and cyclosporine AUC in pediatric HSCT recipients. Pediatric patients who underwent allogeneic myeloablative HSCT and scheduled to receive cyclosporine for aGVHD prophylaxis participated in this multicenter study. Cyclosporine doses were adjusted based on C0 according to each center’s standard of care. Cyclosporine AUC was determined weekly until neutrophil engraftment or Day +42, whichever was later. Associations between severe aGVHD and cyclosporine AUC and other patient and treatment-related factors were evaluated. Of the 110 children enrolled, 97 were evaluable. Thirty-seven (38%) children developed aGVHD; 13 (13.4%) had severe aGVHD. On univariate analysis, there was no association between severe aGVHD and cyclosporine AUC at any time point before engraftment. Future research should focus on refinement of C0 targets for cyclosporine therapeutic drug monitoring in HSCT.

A Systematic Review about an Advance in Cyclosporine Monitoring in Kidney Transplant Recipients

Context: An immunosuppressive drug, Cyclosporine (CsA), has been commonly used in kidney transplants. A safe dosing of CsA often causes nephrotoxity, bone marrow toxicity, and infection. Pharmacokinetic characteristics of CsA and CsA marker relation to the immune suppression have not been completely described in clinical practices yet. Objectives: This review summarizes our achievements on pharmacokinetic and CsA level Marker in kidney transplant patients. Search methods and Selection criteria: A literature review was done using the National Center for Biotechnology Information’s Pubmed Medline, Ovid Medline and Embase, and Iranian registries (Iranmedex, SID, MagIran, and IranDoc). Titles and abstracts were then reviewed to select studies based upon the predefined inclusion criteria. Our study defined a population of adult solid organ transplant recipients receiving the cyclosporine that Cyclosporine monitoring was done. Data Collection and Analysis: Two reviewers independently appraised the quality of each trial and extracted the data from the included trials. Results: CsA pharmacokinetics is very different between kidney transplant recipients, in order to CsA profiling, no pharmacodynamic tools has been confirmed yet in clinical practices and the best way to individualize calcineurin inhibitor therapy is still a controversial issue. C0 levels do not exactly predict the CsA level or rejection risk, patient monitored by C2 levels have upper doses of CsA and have a lower frequency of early acute allograft rejection than patients profiled with C0 and although CA is highly heterogeneous closely post-transplant and seems to be unhelpful early after post-transplant it is more favorable after first months after. Conclusions: Establishing a biological CsA marker may be helpful in clinical decisions on the dose. It seemed to be logical that we should re-inspect the possibility of using them as a supplementary tool towards better therapeutic drug monitoring of cyclosporine or it needs to be reevaluated and needs to find a new target for a therapeutic plan in kidney transplant patients.

Propofol, midazolam, vancomycin and cyclosporine therapeutic drug monitoring in extracorporeal membrane oxygenation circuits primed with whole human blood.

IntroductionAs a result of drug sequestration and increased volume of distribution, the extracorporeal membrane oxygenation (ECMO) procedure might lead to a decrease in drug concentrations during a patient’s treatment. The aim of this study was to evaluate sedative, antibiotic and immunosuppressive drug loss in ECMO circuit using ex-vivo and in-vitro experiments.MethodsBlood concentrations of propofol, midazolam, cyclosporine and vancomycin were measured in an ex-vivo ECMO circuit primed with whole human blood, and compared to controls stored in polypropylene tubes. In vitro experiments were also conducted to further explore the role of temperature, oxygen exposure and polyvinylchloride surfaces on propofol loss in the ECMO circuit.ResultsPropofol concentration decreased rapidly; 70% of its baseline concentration was lost after only 30 minutes, and only 11% remained after five hours (P <0.001 for the comparison with control polypropylene tube propofol concentration). Further experiments demonstrated that oxygen exposure and contact with polyvinylchloride tubing were respectively responsible for 70% and 85% of propofol loss after 45 minutes. Midazolam concentration also rapidly decreased in the ECMO circuit, with only 54% and 11% of baseline concentration being detected at 30 minutes and 24 hours respectively (P = 0.01 versus control). Alternatively, cyclosporine concentration remained stable for the five first hours, then decreased to 78% and 73% of the baseline value after 24 hours and 48 hours, (P = 0.35 versus control). Lastly, vancomycin concentration remained stable in the ECMO circuit for the 48-hour experimental protocol.ConclusionsWe observed important losses of propofol and midazolam, while cyclosporine concentration decreased slowly and moderately, and vancomycin concentration remained unchanged in the ex-vivo ECMO circuit primed with whole human blood. These data might help intensive care unit physicians planning clinical trials with a final objective to better adapt doses of these drugs while treating critically ill ECMO patients.

Population pharmacokinetics and Bayesian estimation of cyclosporine in a Tunisian population of hematopoietic stem cell transplant recipient

Therapeutic drug monitoring of cyclosporine minimizes the risk of toxicity and acute rejection after transplantation. Areas under the curve (AUCs) rather than trough concentration-based monitoring are recommended. Population pharmacokinetics (PopPK) modeling and Bayesian estimation seem to be the best way to predict cyclosporine disposition and dose requirements to achieve the therapeutic target in an individual patient because of the possibility of predicting cyclosporine AUC using only a few blood samples. Our objectives were to build a PopPk model for cyclosporine in a Tunisian population of HSCT patients and to develop a Bayesian method for the estimation of individual cyclosporine AUC. The PopPk of cyclosporine was studied using nonlinear mixed effects modeling (NONMEM) in 30 patients (index group) receiving cyclosporine on a twice-daily basis. Ten blood samples were collected after steady-state morning cyclosporine dose. Bayesian estimation of individual AUC was made on the basis of three blood concentration measurements in an independent group of 30 patients (test group). A two-compartment model with first-order absorption and a lag time provided the best fitting. The population mean estimate and interindividual variability from the final model for CL, Ka, Tlag, V1, V2, and Q were 25.4 L/h (CV = 38.72 %), 0.214 h(-1)(CV = 28.5 %), 0.382 h, 10.9 L (85.73 %), 496 L, and 5 L/h, respectively. Covariates had no discernible effects on cyclosporine pharmacokinetics in our population. Bayesian estimation provided an accurate estimation of AUC, although a bias was observed leading to slight underprediction of AUC (bias -1.03 %). A very satisfactory precision was observed (RMSE 12.07 %). We report a PopPK model for cyclosporine in Tunisian HSCT patients. Bayesian estimation using only three concentrations provides good prediction of cyclosporine exposure. These tools allow us to routinely estimate cyclosporine AUC in a clinical setting.

The Concentration of Cyclosporine Metabolites Is Significantly Lower in Kidney Transplant Recipients With Diabetes Mellitus

Diabetes mellitus is prevalent among kidney transplant recipients. The activity of drug metabolizing enzymes or transporters may be altered by diabetes leading to changes in the concentration of parent drug or metabolites. This study was aimed to characterize the effect of diabetes on the concentration of cyclosporine (CsA) and metabolites. Concentration-time profiles of CsA and metabolites (AM1, AM9, AM4N, AM1c, AM19, and AM1c9) were characterized over a 12-hour dosing interval in 10 nondiabetic and 7 diabetic stable kidney transplant recipients. All patients were male, had nonfunctional CYP3A5*3 genotype, and were on combination therapy with ketoconazole. The average daily dose (±SD) of CsA was 65 ± 21 and 68 ± 35 mg in nondiabetic and diabetic subjects, respectively (P = 0.550). Cyclosporine metabolites that involved amino acid 1 (AM1, AM19, AM1c) exhibited significantly lower dose-normalized values of area under the concentration-time curve in patients with diabetes. Moreover, during the postabsorption phase (≥3 hours after dose), metabolite-parent concentration ratios for all metabolites, except AM4N, was significantly lower in diabetic patients. The pharmacokinetic parameters of ketoconazole were similar between the 2 groups thus excluding inconsistent ketoconazole exposure as a source of altered CsA metabolism. This study indicates that diabetes mellitus significantly affects the concentration of CsA metabolites. Because CsA is eliminated as metabolites via the biliary route, the decrease in the blood concentration of CsA metabolites during postabsorption phase would probably reflect lower hepatic cytochrome P450 3A4 enzyme activity. However, other mechanisms including altered expression of transporters may also play a role. Results of cyclosporine therapeutic drug monitoring in diabetic patients must be interpreted with caution when nonspecific assays are used.

Development and Validation of Limited Sampling Strategies for Estimation of Cyclosporine Area Under the Concentration–Time Curve in Hematopoietic Stem Cell Transplant Patients

The aim of this study was to develop and validate limited sampling strategies for accurately predicting 12-hour area under the concentration-time curve (AUC(0-12 h)) to provide a practical method for more precise therapeutic drug monitoring of cyclosporine A in stem cell transplant patients. Steady-state cyclosporine blood concentrations were measured within a dosing interval (12 hours post administration) in 35 allogeneic bone marrow transplant patients receiving 238 mg (±117 mg) twice-daily dose of cyclosporine. Limited sampling strategies were developed by multiple linear regression analysis of relationship between cyclosporine A full AUC(0-12 h) values and different combinations of preselected blood concentrations. Validation of the estimating equations was done by a bootstrap-like cross-validation method. Cross-validation results showed that cyclosporine AUC(0-12 h) could be estimated using either 2 or 3 samples within the first 4 hours after drug administration with good accuracy and precision (absolute prediction error of less than 6.2%). The number of estimated area under the drug concentration-time curves within 15% of observed values was greater than 26 (74%) for models used predose concentration with either c(2h) and c(4h) or both. Most of the previously reported single-sample models showed a systematic error in predicting AUC(0-12 h). Although a statistically significant difference in precision of prediction was seen between 3-sample model using c(0), c(2h), and c(4h) and 2-sample models (c(0), c(2h) or c(0), and c(4h)), such a difference (2%) could not be of clinical importance. Other 2-sample estimating equations (models using c(2h) with either c(6h) or c(10h)) with the same degree of precision appear to be less feasible clinically. Cyclosporine AUC(0-12 h) in bone marrow transplant patients could be estimated using 2 or 3 samples within the first 4 hours after drug administration with good accuracy and precision.

Potential of Dried Blood Self-Sampling for CyclosporineC2Monitoring in Transplant Outpatients

Background. Close therapeutic drug monitoring of Cyclosporine (CsA) in transplant outpatients is a favourable procedure to maintain the long-term blood drug levels within their respective narrow therapeutic ranges. Compared to basal levels (C0), CsA peak levels (C2) are more predictive for transplant rejection. However, the application of C2 levels is hampered by the precise time of blood sampling and the need of qualified personnel. Therefore, we evaluated a new C2 self-obtained blood sampling in transplant outpatients using dried capillary and venous blood samples and compared the CsA levels, stability, and clinical practicability of the different procedures. Methods. 55 solid organ transplant recipients were instructed to use single-handed sampling of each 50 μL capillary blood and dried blood spots by finger prick using standard finger prick devices. We used standardized EDTA-coated capillary blood collection systems and standardized filter paper WS 903. CsA was determined by LC-MS/MS. The patients and technicians also answered a questionnaire on the procedure and sample quality. Results. The C0 and C2 levels from capillary blood collection systems (C0 [ng/mL]: 114.5 ± 44.5; C2: 578.2 ± 222.2) and capillary dried blood (C0 [ng/mL]: 175.4 ± 137.7; C2: 743.1 ± 368.1) significantly (P < .01) correlated with the drug levels of the venous blood samples (C0 [ng/mL]: 97.8 ± 37.4; C2: 511.2 ± 201.5). The correlation at C0 was ρ cap.-ven. = 0.749, and ρ dried blood-ven = 0.432; at C2: ρ cap.-ven. = 0.861 and ρ dried blood-ven = 0.711. The patients preferred the dried blood sampling because of the more simple and less painful procedure. Additionally, the sample quality of self-obtained dried blood spots for LC-MS/MS analytics was superior to the respective capillary blood samples. Conclusions. C2 self-obtained dried blood sampling can easily be performed by transplant outpatients and is therefore suitable and cost-effective for close therapeutic drug monitoring.

A Review of the Immunosuppressive Activity of Cyclosporine Metabolites:New Insights into an Old Issue

Cyclosporine A (CsA) is metabolized into a vast spectrum of metabolites. The potential immunosuppressive action of CsA's metabolites has been studied extensively in the early 1990's, with conflicting and inconclusive results. Since then, the pharmacological and clinical consensus guidelines recommend the use of specific monoclonal assays for measurement of CsA's concentrations thus avoiding metabolite interference. Nevertheless, clinical benefit or superiority of these assays was never convincingly demonstrated. We provide a review of the performed in vivo, in vitro and animal studies and their conclusions. During the last years, many transplantation centres have employed the C(2) monitoring of CsA (2 hours post-dose concentration). The metabolites / parent drug ratio two hours post dose is completely different from trough levels (predose concentration). Cyclosporine exerts its immunosuppressive action by inhibiting the enzyme calcineurin phosphatase (CaN). Currently, our laboratory, among others, is working on determination of the enzyme's inhibition and its potential use as a pharmacodynamic biomarker. Utilizing this novel pharmacodynamic approach, we have performed in vitro and in vivo studies investigating the immunosuppressive impact of CsA's metabolites on C2 monitoring and on various monitoring assays (mono-/polyclonal). Interestingly, even though we have estimated in vivo that the potential immunosuppressive action of metabolites is less than 10% of the parent drug, we have found assays that take metabolites into consideration to correlate stronger with calcineurin phosphatase inhibition. We believe that the old controversial issue of metabolite induced immunosuppressive action examined under the light of newer pharmacodynamic approaches is still intriguing. Instead of a priori neglecting CsA's metabolites maybe we should investigate the potential of utilizing them as an additional tool towards better therapeutic drug monitoring of cyclosporine.

Population Pharmacokinetics of Cyclosporine in Chinese Cardiac Transplant Recipients

To characterize the population pharmacokinetics of cyclosporine in Chinese patients undergoing cardiac transplantation and to identify the demographic and clinical covariates affecting cyclosporine clearance. Population pharmacokinetic analysis using data from a retrospective chart review. Specialty hospital in Hong Kong for treatment of cardiac and pulmonary diseases. Thirty-eight Chinese adult patients (mean age 46 yrs) who had undergone routine cyclosporine therapeutic drug monitoring after cardiac transplantation between January 1, 1991, and December 31, 2003. Data regarding dosing, demographics, clinical laboratory values, and concurrent drugs were collected retrospectively. Data were included if patients had blood cyclosporine concentrations determined for at least 12 weeks after transplantation; an average of 18 blood samples/patient were collected. Population modeling was performed using a one-compartment linear model with first-order absorption and elimination. Various demographic and clinical covariates were tested for their significant effects on the apparent oral clearance (Cl/F) of cyclosporine. The stability of the final population model was evaluated by using the bootstrap resampling method. Statistically significant associations were observed between Cl/F and each of the following covariates: body weight (BW), use of diltiazem (DIL), and hematocrit value (HCT). The final model was Cl/F=5.00*(1-DIL)+365/HCT+(0.144*BW). The interindividual variabilities of Cl/F and apparent volume of distribution were 14.5% and 40.2%, respectively. The mean parameter estimates obtained from bootstrap analyses were highly consistent with those obtained with the original data set. The estimated Cl/F values of cyclosporine in our Chinese cardiac transplant recipients appeared to be similar to those reported for Caucasian cardiac transplant recipients. Thus, our data provide support that a cyclosporine dosage regimen similar to that in Caucasian patients may be needed in Chinese cardiac transplant recipients. However, further studies are required to determine the optimum cyclosporine dosage regimen in the Chinese population.

A Randomized, Controlled Trial of C 0- Vs C 2-guided Therapeutic Drug Monitoring of Cyclosporine in Stable Heart Transplant Patients

Cyclosporine monitoring using 2-hour post-dose samples (C2) is thought to be more efficacious than using pre-dose levels (C0) in managing immunosuppression for transplant patients. We evaluated the effect of C2 monitoring on cyclosporine dose and clinical parameters in stable heart transplant patients. 125 stable heart transplant patients were randomized to C0 or C2 monitoring of cyclosporine levels for a period of six months. All patients had both C0 and C2 samples taken, and clinicians were blinded to one of the samples depending on randomization. The primary endpoint was the relative change in cyclosporine (Neoral) dose during the study period and secondary endpoints were change in creatine clearance, mortality, infection, and acute rejection. There was a significant decrease in the cyclosporine dose for the C2 group as compared with the C0 group (-11 mg/day and -26 mg/day respectively, p = 0.0025). No proven rejection episodes occurred in either group and there was no significant difference in the incidence of infection (C0 6, C2 10; p = 0.14), the change in renal function (change in creatine clearance C(0) +0.54 ml/min; C2 -0.16 ml/min; p = 0.61), the number of blood tests or dose adjustments between groups over the study period. Analysis of the blinded samples revealed that the reduction of cyclosporine dose in the C2 group could not be accounted for by reduced immunosuppression . C2 monitoring allows a significant cyclosporine dose reduction without compromising patient outcome in stable heart transplant patients. Further studies are required to ascertain whether this dose reduction can be translated into clinical benefit.

Cyclosporine Monitoring With 2-Hour Postdose Levels in Heart Transplant Recipients

Cyclosporine therapeutic drug monitoring based on 2-hour postdose concentration (C2) compared with conventional trough concentration (C0) can improve clinical outcomes for de novo renal and liver transplant patients. However, in heart transplant patients, published studies are limited. To determine the clinical significance of C2 compared with C0 following orthotopic heart transplantation, the authors measured CsA at C0 and C2 and estimated CsA area under the curve (AUC) using Bayesian estimation and 4 sparse sample algorithms in a cross section of 31 adult patients receiving triple-drug immunosuppression with CsA, mycophenolate mofetil (MMF), and prednisone. CsA was measured using a validated HPLC method. Endomyocardial biopsies were graded based on the ISHLT system. Mean +/- SD values for CsA dose, C0, and C2 were 4.8 +/- 1.4 mg/kg/d, 240 +/- 62 microg/L, and 1319 +/- 469 microg/L, respectively. Correlation with AUC, using different estimation algorithms, was better for C2 (r(2) = 0.79-0.99) than for C0 (r(2)= 0.11-0.52). The mean +/- SD values for C0 (microg/L) and C2 (microg/L) for rejectors (n = 3) were 215 +/- 68 and 949 +/- 204 versus 242 +/- 62 and 1359 +/- 474 for the nonrejectors (P = 0.66 and 0.12, respectively). Fisher exact test P values using the median as threshold value for C0 and C2 (234 microg/L and 1251 microg/L, respectively) were 0.6 and 0.1. Analysis of the data revealed that C0 values in rejectors have wider variability than C2. There were no rejectors among the 16 patients exceeding the C2 median value; for C0, however, there was not an easily identifiable threshold value. There is a trend for a significant relationship between C2 and the incidence of rejection, but the number of rejectors was too small to reach statistical significance. A prospective concentration-control de novo study design is recommended as the most appropriate way to fully evaluate the potential utility of C2 monitoring in heart transplant patients.

A role for cytokine measurement in therapeutic monitoring of immunosuppressive drugs following lung transplantation

The strength of the allo-immune response to a transplanted organ [1,2] currently mandates combined pharmacological immunosuppression to prevent rejection. The calcineurine inhibitor Cyclosporine remains an important component of immunosuppression regimens post lung transplantation with the International Registry of Heart and Lung Transplantation recording 50% of patients receiving this drug. Cyclosporine requires therapeutic drug monitoring with the aim of maximizing efficacy whilst minimizing the risk of toxicity. Historically the trough (predose or Co) level has been used to guide the dose of cyclosporin and the dose range in lung transplantation has been determined by rather empirical review of studies in kidney transplantation [3]. A survey conducted in 1994–95 showed that most lung transplant centres however, recommended a higher range of target concentrations during the early post operative period [4]. The recommended therapeutic blood concentrations however, are broad and may vary according to the clinical situation and the choice of other immunosuppressive agents being administered. Relatively recent data has supported the use of therapeutic drug monitoring of cyclosporin by the use of whole blood drawn two hours after administration of the dose (C2) with data showing a better prediction of clinical effect [5]. Nevertheless therapeutic drug monitoring has certain general limitations with the concentration measured in blood, not necessarily the concentration of the drug at the site of action. The alternative approach, as discussed in a study by Hodge and colleagues in the January 2005 issue of Clinical and Experimental Immunology is to measure the therapeutic action of the drug either directly or indirectly [6]. In general the approaches involve in vitro assessment of T cell activation by measuring cytokine release from peripheral circulating cells either in the resting or stimulated state [7–9]. Whilst these techniques have great potential, it is not yet established whether they are predictive of clinical events. Moreover the complexity of the allo-immune response may make it difficult to model using such assays. There is also a problem regarding which compartment of the immune system should one study in order to give the best biological information. Most studies use peripheral circulating cells rather than intragraft immune cells which may be more relevant in terms of effecting graft injury. In a broad sense, the process of immune cell-mediated allograft rejection is regulated by an array of cytokines. Some of these, for example the chemokines, are produced by stressed graft cells and activated immune cells whilst others, such as IL-2 and IL-4, are produced by activated immune cells. Given the importance of this range of cytokines, it is perhaps surprising that immunosuppressive calcineurin inhibitors such as Cyclosporin A (Cs-A) are effective as they directly regulate the expression of only a very limited range of cytokines. This includes blockade of de novo expression of the T cell growth factor IL-2 following the activation of resting T cells [10] and up-regulation of the expression of TGF-β by a range of parenchymal cells [11]. Clearly the analysis of cytokine expression has the potential to provide clinically useful information about the state of allograft rejection or acceptance. However, a number of issues must first be addressed, including:

Therapeutic drug monitoring of cyclosporine

Therapeutic drug monitoring of cyclosporine has been established as part of the routine clinical treatment for patients after organ transplantation. The inability to define optimal dose (maximize efficacy/minimize toxicity) has been a problem related to drug monitoring of cyclosporine. The original cyclosporine formula showed high intra-patient and inter-patient variability and low bioavailability. The microemulsion formulation of cyclosporine (Neoral) was introduced to address the absorption problems related to the original cyclosporine formulation. With the introduction of Neoral, renewed interest in methods of therapeutic drug monitoring brought us from trough monitoring (C0) to levels measured 2 hours after dosing (C2). The pharmacokinetic rationale for using C2 to monitor patients receiving Neoral has demonstrated a reduced incidence of rejection in de novo patients and improvements in safety profile in both renal and hepatic transplant recipients. Monitoring C2 levels is a more precise method for optimizing cyclosporine dosing and a better way to individualize therapy. Further data are required from prospective trials to evaluate the clinical benefits of adopting C2 monitoring in cardiac and lung transplant recipients as well as in long-term maintenance patients.

Therapeutic drug monitoring of cyclosporine

The introduction of cyclosporine into clinical practice improved transplant outcome. However, the use of cyclosporine is not without problems. A narrow therapeutic index (the drug causes irreversible kidney damage when given in too high a dose) coupled with variable absorption and unpredictable pharmacokinetics has resulted in the need to measure cyclosporine blood concentrations to enable the dose of the drug to be individualised to the patient. When this is done correctly therapeutic efficacy can be maximised while toxicity is kept to a minimum. The evolution of cyclosporine dose optimisation started with the adjustment of empirical fixed doses by clinical “judgement;” progressed to therapeutic drug monitoring of trough, predose, C0 concentration with non specific assays that measured parent drug and metabolite; then on to “specific” cyclosporine C0 measurements; through area under curve monitoring using full profile measurements and limited sampling scheme procedures; and finally ending up with absorption profiling that targets AUC in the first 4 hours or the 2 hour blood cyclosporine concentration, C2. At the same time the formulation of cyclosporine has changed from Sandimmune to Neoral and now generic forms of the latter are available. The evidence base supporting C2 monitoring continues to grow and the technique will need to be customised as new combination therapies emerge. Therapeutic drug monitoring of cyclosporine may also need to be tailored to avoid the potential negative impact of switching patients to generic forms of the drug.