Patient management by Neoral C(2) monitoring: an international consensus statement

LC-MS/MS and EMIT measure the whole blood concentration of cyclosporine A: The two methods yield concordant results within the dynamic range of the latter, but the former shows broader application scenarios

Cyclosporine A (CsA) is a widely used immunosuppressive drug with a narrow therapeutic index and large individual differences. Its therapeutic and toxic effects are closely related to blood drug concentrations, requiring routine therapeutic drug monitoring (TDM). The current main methods for TDM of CsA are enzyme multiplied immunoassay technique (EMIT) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). However, few study on the method comparison of the EMIT and LC-MS/MS for the measurement of whole blood CsA concentration in children has been reported. In this study, we developed a simple and sensitive LC-MS/MS assay for the determination of CsA, and 657 cases of CsA concentrations were determined from 197 pediatric patients by a routine EMIT assay and by the validated in-house LC-MS/MS method on the same batch of samples, aimed to address the aforementioned concern. Consistency between the two assays was evaluated using linear regression and Bland-Altman analysis. The linear range of LC-MS/MS was 0.500-2000 ng/mL and that of the EMIT was 40-500 ng/mL, respectively. Overall, the correlation between the two methods was significant (r-value ranging from 0.8842 to 0.9441). Unsatisfactory consistency was observed in the concentrations < 40 ng/mL (r = 0.7325) and 200-500 ng/mL (r = 0.6851). Bland-Altman plot showed a mean bias of -18.0 % (±1.96 SD, -73.8 to 37.8 %) between EMIT and LC-MS/MS. For Passing-Bablok regression between EMIT and LC-MS/MS did not differ significantly (p > 0.05). In conclusion, the two methods were closely correlated, but the CsA concentration by LC-MS/MS assay was slightly higher than that by EMIT method. Switching from the EMIT assay to the LC-MS/MS method was acceptable, and the LC-MS/MS method will receive broader application in clinical settings due to its better analytical capabilities, but the results need to be further verified in different laboratories.

Therapeutic drug monitoring in kidney and liver transplantation: current advances and future directions

INTRODUCTION

Immunosuppressive drugs (ISD) present a narrow therapeutic window and extremely high inter- and intra-individual pharmacokinetic variability, which complicates their use in solid organ transplant recipients. In order to find a narrow appropriate equilibrium for each patient with the aim of maintaining clinical efficacy and reducing the risk of adverse drug reactions, a complex both clinical and biological monitoring is required, in particular through the use of therapeutic drug monitoring (TDM).

AREA COVERED

This review provides an overview of the available information on the relationship between exposure to immunosuppressive drugs and their efficacy and/or toxicity in kidney and liver transplantation. The aim of the review is to describe the pharmacodynamic/pharmacokinetic relationship that exists for immunosuppressive drugs, to summarize the studies that assess the value of TDM for these drugs in clinical practice, and to present the target and monitoring strategies aimed at optimizing patient immunosuppression, which could help to take a step forward in the field of solid organ transplant patient care.

EXPERT OPINION

To improve the care of transplant patients, several TDM innovations can be pursued by investigators. Among these, the development of microsampling methods for TDM or the combination of pharmacodynamic biomarkers with ISD exposure measurements appear to be relevant strategies.

Effects of diurnal variation of bile acids by meal on cyclosporine A absorption

BACKGROUND

Stabilizing blood levels with microemulsified cyclosporine A (CsA), administered in many pediatric kidney diseases, is important for effective immunosuppression and reduced nephrotoxicity. CsA is affected by total bile acids (TBAs); however, no reports have simultaneously measured both. We aimed to elucidate the hypothesized relationship between TBA levels and diurnal variation in CsA in children.

METHODS

We retrospectively reviewed the medical records of children who were taking oral CsA for the treatment of kidney diseases between January 2016 and July 2021. They consumed four balanced meals and snacks during the day. CsA and TBA were measured twice, in pairs, before and at 0.5, 1, 1.5, 2, 3, and 4 h after oral administration in the morning and evening, and the four-h area under curve (AUC)_0-4 of CsA and trough-to-peak ratio (TPR) of TBA were compared.

RESULTS

Fifty-eight pairs were measured in total; 12 children had idiopathic nephrotic syndrome and 4 children had immunoglobulin A vasculitis with nephritis. The median age at measurement was 7.5 years and the dose of CsA was 3.8 mg/kg/day. The AUC_0-4 (ng·h/mL) was significantly lower in the evening than in the morning (1,669 vs. 1,451, P < 0.001). The TPR of TBA was significantly higher in the evening than in the morning (0.14 vs. 0.25, P < 0.001).

CONCLUSIONS

The low AUC_0-4 and slow TBA secretion observed in the evening may be due to pediatric-specific dietary rhythms; thus, snack timing should be considered in children for stabilizing CsA levels.

A Comprehensive Review of Calcineurin Inhibitors Used for Immunosuppression in Cardiac Transplantation

Calcineurin inhibitors (CNIs) have been the foundation of immunosuppression in solid organ transplantation since the 1980s. Cyclosporine A (CSA), the first in class, was identified as the metabolite of the soil fungus Tolypocladium inflatum Gams as part of a larger program of screening for naturally occurring fungal metabolites with biologic activity in the 1970s. Significant immunosuppressive effects were discovered and consequently CSA was trialed as an immunosuppressant in renal transplantation. This initial success led to its widespread study and adoption in solid organ transplantation. This novel agent yielded significant improvements in both 1 year and longer-term allograft and patient survival. Subsequently, a similar and more potent CNI, tacrolimus was developed. Today, it is the principal CNI used for prevention of allograft rejection. Like all other immunosuppressives, the benefits of CNIs are counterbalanced by side effects and complications resulting from drug toxicity. This chapter comprehensively reviews the clinical use of CNIs in cardiac transplantation.

Immunosuppression in Lung Transplantation

Immunosuppression in lung transplantation is an area devoid of robust clinical data. This chapter will review the history of immunosuppression in lung transplantation. Additionally, it will evaluate the three classes of induction, maintenance, and rescue immunosuppression in detail. Induction immunosuppression in lung transplantation aims to decrease incidence of lung allograft rejection, however infectious risk must be considered when determining if induction is appropriate and which agent is most favorable. Similar to other solid organ transplant patient populations, a multi-drug approach is commonly prescribed for maintenance immunosuppression to minimize single agent drug toxicities. Emphasis of this review is placed on key medication considerations including dosing, adverse effects, and drug interactions. Clinical considerations will be reviewed per drug class given available literature. Finally, acute cellular, antibody mediated, and chronic rejection are reviewed.

Cyclosporine A C1.5 monitoring reflects the area under the curve in children with nephrotic syndrome: a single-center experience

BACKGROUND

The currently used single-monitoring method for drug-blood-level evaluation in cyclosporine A (CsA) treatment for nephrotic syndrome (NS) was established through hourly measurements based on adult organ transplantation. However, the pharmacokinetics may differ due to different concomitant medications, age, and conditions. This study was conducted to determine the measurement timing that best reflects the CsA area under the curve (AUC) in pediatric NS.

METHODS

This retrospective study included children aged 2-14 years who were started on CsA treatment for idiopathic NS during 2013-2020. AUC_0-4 was calculated from 7 points, before and 0.5, 1, 1.5, 2, 3, and 4 h after administration. Mean values at each timing were compared with age-dependent different drug forms. Correlation between AUC_0-4 and measurement timing was analyzed.

RESULTS

There were 13 patients (11 boys) whose median age during testing was 7.3 years, and the total number of measurements was 94. The highest timing of CsA concentrations was found in C₁ 59.6%. The content liquid used at younger ages had a faster absorption time to peak value and lower blood concentration than those of capsules. Among the significant correlations observed, AUC_0-4 and C_1.5 showed the strongest significant correlation coefficient (r = 0.93, P < 0.001).

CONCLUSION

In pediatric NS, CsA metabolism may be faster than that in previous organ transplantation. Compared with C₂, C_1.5 monitoring may result in better disease control as it can best reflect the AUC_0-4 and peak values associated with side effects, which are indicators of therapeutic efficacy.

Development of a Population Pharmacokinetic Model for Cyclosporine from Therapeutic Drug Monitoring Data

Aim

To develop a population pharmacokinetic model for Uruguayan patients under treatment with cyclosporine (CsA) that can be applied to TDM. Patients and Methods. A total of 53 patients under treatment with CsA were included. 37 patients with at least one pharmacokinetic profile described with four samples were considered for model building, while the remaining 16 were considered for the assessments of predictive performances. Pharmacokinetic parameter estimation was performed using a nonlinear mixed effect modelling implemented in the Monolix® software (version 2019R1, Lixoft, France); meanwhile, simulations were performed in R v.3.6.0 with the mlxR package.

Results

A two-compartment model with a first-order disposition model including lag time was used as a structural model. The final model was internally validated using prediction corrected visual predictive check (pcVPC) and other graphical diagnostics. A total of 621 CsA steady-state concentrations were analyzed for model development. Population estimates for the absorption constant (ka) and lag time were 0.523 h⁻¹ and 0.512 h, respectively; apparent clearance (CL/F) was 30.3 L/h (relative standard error [RSE] ± 8.25%) with an interindividual variability of 39.8% and interoccasion variability of 38.0%; meanwhile, apparent clearance of distribution (Q/F) was 17.0 L/h (RSE ± 12.1%) with and interindividual variability of 53.2%. The covariate analysis identified creatinine clearance (ClCrea) as an individual factor influencing the Cl of CsA. The predictive capacity of the population model was demonstrated to be effective since predictions made for new patients were accurate for C1 and C2 (MPPEs below 50%). Bayesian forecasting improved significantly in the second and third occasions.

Conclusion

A population pharmacokinetic model was developed to reasonably estimate the individual cyclosporine clearance for patients. Hence, it can be utilized to individualize CsA doses for prompt and adequate achievement of target blood concentrations of CsA.

Correlation between Cyclosporine Blood Levels and Area under Blood Concentration Time Curve in Iraqi Bone Marrow Transplant Patients Treated with Neoral® Oral Solution

Cyclosporine is a potent immunosuppressive drug. It has a narrow therapeutic index, and therefore the measurement of cyclosporine’s blood concentration is essential to obtain optimal therapy. Measurement of the area under the blood concentration-time curve (AUC) is reflective of total drug exposure. However, for organ transplant patients, the measurement of AUC involves many problems and difficulties. Thus, it is more clinically acceptable to use a single blood sample as a surrogate index of total drug exposure. Fifty-four adults bone marrow transplant Iraqi patients were given cyclosporine every 12 h as prophylaxis using Neoral® oral solution. Steady-state blood concentrations were monitored for each patient at zero time and then at 1, 2, 3, 4, 6, 8, 10, and at 12 h post-dosing. Cyclosporine blood levels were determined by using AXSYM automated immuno-analyzer which is a fluorescence polarization immunoassay (FPIA). The present investigation demonstrated the best correlation between C2 and the corresponding AUC0–4h and AUC0–12h compared to other concentrations. After two months of cyclosporine therapy, no unexpected biochemical changes and adverse effects were registered. It is concluded from this study that a single blood sample obtained at 2 h post-dosing (C2) and possibly at 3 h post dosing (C3) are ideal surrogate indexes for reflecting total drug exposure, and therefore may be used in clinical practice for predicting therapeutic and toxic effects of cyclosporine.

Interaction of cyclosporine with phenobarbital in cats: a preliminary study

Phenobarbital (PB) decreases the cyclosporine (CsA) blood level in humans. However, the interaction of PB with CsA has not been reported in cats. This study investigated the effects of multiple doses of PB on the pharmacokinetics of CsA in three healthy cats. The treatments included oral CsA 5 mg/kg alone and oral CsA 5 mg/kg plus PB 5 mg/kg for 4 weeks. Co-administration of PB with CsA resulted in significant decreases in the oral bioavailability of CsA though both the first pass and elimination phases. These preliminary results suggest that oral administration of multiple doses of PB increases the required CsA dosage in CsA-based immunosuppressive therapy in cats.

Cyclophilin D knockout protects the mouse kidney against cyclosporin A-induced oxidative stress

Mitochondrial dysfunction and oxidative stress have been implicated in cyclosporin A (CsA)-induced nephrotoxicity. CsA interacts with cyclophilin D (CypD), an essential component of the mitochondrial permeability transition pore and regulator of cell death processes. Controversial reports have suggested that CypD deletion may or may not protect cells against oxidative stress-induced cell death. In the present study, we treated wild-type (WT) mice and mice lacking CypD [peptidylprolyl isomerase F knockout (Ppif-/-) mice] with CsA to test the role and contribution of CypD to the widely described CsA-induced renal toxicity and oxidative stress. Our results showed an increase in the levels of several known uremic toxins as well as the oxidative stress markers PGF2α and 8-isoprostane in CsA-treated WT animals but not in Ppif-/- animals. Similarly, a decline in S-adenosylmethionine and the resulting methylation potential indicative of DNA hypomethylation were observed only in CsA-treated WT mice. This confirms previous reports of the protective effects of CypD deletion on the mouse kidney mediated through a stronger resistance of these animals to oxidative stress and DNA methylation damage. However, a negative effect of CsA on the glycolysis and overall energy metabolism in Ppif-/- mice also indicated that additional, CypD-parallel pathways are involved in the toxic effects of CsA on the kidney. In summary, CsA-mediated induction of oxidative stress is associated with CypD, with CypD deletion providing a protective effect, whereas the reduction of energy production observed upon CsA exposure did not depend on the animals' CypD status.

Pharmacodynamic monitoring using biomarkers to individualize pharmacotherapy

Drug doses are often titrated upon their clinical effects (e.g., blood pressure). Unfortunately, for many drugs there is no direct, clinical read-out to estimate dose adequateness. Alternatively, drug dosing is based on the maximum tolerated dose approach or therapeutic drug monitoring. However, the concentration-response curves may be flattened or bell-shaped as suggested for some ‘biologicals’. Together, these aspects raise the question why drug dosing is not individualized by pharmacodynamic monitoring. Evaluating the effects of drugs at their pharmacological target or meaningful biomarkers might indicate nonresponders, objectively quantify the maximum molecular effect and thus restrict overdose and underdosing. This review outlines the theory and biological or technical prerequisites for biomarker-based pharmacodynamic monitoring, and highlights selected examples from different fields of clinical medicine.

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.

Efficacy and safety of combination therapy with prednisolone and oral tacrolimus for progressive interstitial pneumonia with systemic sclerosis: A retrospective study

OBJECTIVES

We retrospectively investigated efficacy and safety of combination therapy with prednisolone (PSL) and tacrolimus (TAC) for progressive interstitial pneumonitis with systemic sclerosis (SSc-PIP).

METHODS

We studied 11 patients with SSc-PIP who received combination therapy with PSL (0.5 mg/kg/d) and TAC (3 mg/d).

RESULTS

Baseline Hugh-Jones grades were I, II, III, and IV in 2, 6, 2, and 1 patients, respectively. Krebs von den Lungen-6 (KL-6) values were elevated to 914 (range 300-2614) U/mL. % Diffusing capacity of carbon monoxide (%DLco) remarkably decreased to 47.4 (range 9.7-64.4) %. All patients were alive at 1 year after therapy. In response to treatment, interstitial pneumonia (IP) improved in three patients, stable in seven patients, and deteriorated in one patient. Total ground-glass opacity (GGO) score improved (p = .005). No significant changes occurred in values of KL-6, % forced vital capacity (%FVC), and %DLco. Presently, all seven patients who could be followed up were alive. IP improved in three patients and stable in four patients. Total GGO score improved (p = .016). KL-6, %FVC, and %DLco did not change. Mild cytomegalovirus or herpes zoster infection occurred in two patients. Grade I renal injuries were observed in three and one patient at 1 year and present, respectively.

CONCLUSION

Combination therapy with PSL and TAC appeared to be well tolerated and effective in suppressing the disease activity of SSc-PIP.

Results of ASERTAA, a Randomized Prospective Crossover Pharmacogenetic Study of Immediate-Release Versus Extended-Release Tacrolimus in African American Kidney Transplant Recipients

BACKGROUND

Differences in tacrolimus dosing across ancestries is partly attributable to polymorphisms in CYP3A5 genes that encode tacrolimus-metabolizing cytochrome P450 3A5 enzymes. The CYP3A5*1 allele, preponderant in African Americans, is associated with rapid metabolism, subtherapeutic concentrations, and higher dose requirements for tacrolimus, all contributing to worse outcomes. Little is known about the relationship between CYP3A5 genotype and the tacrolimus pharmacokinetic area under the curve (AUC) profile in African Americans or whether pharmacogenetic differences exist between conventional twice-daily, rapidly absorbed, immediate-release tacrolimus (IR-Tac) and once-daily extended-release tacrolimus (LifeCycle Pharma Tac [LCPT]) with a delayed absorption profile.

STUDY DESIGN

Randomized prospective crossover study.

SETTING & PARTICIPANTS

50 African American maintenance kidney recipients on stable IR-Tac dosing.

INTERVENTION

Recipients were randomly assigned to continue IR-Tac on days 1 to 7 and then switch to LCPT on day 8 or receive LCPT on days 1 to 7 and then switch to IR-Tac on day 8. The LCPT dose was 85% of the IR-Tac total daily dose.

OUTCOMES

Tacrolimus 24-hour AUC (AUC_0-24), peak and trough concentrations (C_max and C_min), time to peak concentration, and bioavailability of LCPT versus IR-Tac, according to CYP3A5 genotype.

MEASUREMENTS

CYP3A5 genotype, 24-hour tacrolimus pharmacokinetic profiles.

RESULTS

∼80% of participants carried the CYP3A5*1 allele (CYP3A5 expressers). There were no significant differences in AUC_0-24 or C_min between CYP3A5 expressers and nonexpressers during administration of either IR-Tac or LCPT. With IR-Tac, tacrolimus C_max was 33% higher in CYP3A5 expressers compared with nonexpressers (P=0.04): With LCPT, this difference was 11% (P=0.4).

LIMITATIONS

This was primarily a pharmacogenetic study rather than an efficacy study; the follow-up period was too short to capture clinical outcomes.

CONCLUSIONS

Achieving therapeutic tacrolimus trough concentrations with IR-Tac in most African Americans results in significantly higher peak concentrations, potentially magnifying the risk for toxicity and adverse outcomes. This pharmacogenetic effect is attenuated by delayed tacrolimus absorption with LCPT.

TRIAL REGISTRATION

Registered at ClinicalTrials.gov, with study number NCT01962922.

Update on Immunosuppressive Drugs Used in Solid-Organ Transplantation and Their Nutrition Implications

The success of solid organ transplantation rests heavily on the major advances in immunosuppressive therapy. The early years of organ transplantation were plagued with high failure rates and frequent episodes of acute rejection. With the introduction of improved immunosuppressive agents, successful organ transplantation has become the norm. The emphasis of immunosuppressive therapy has shifted from preventing rejection to balancing acceptable rates of rejection with moderation in adverse effects of the immunosuppressive agents. Among the many possible adverse effects of immunosuppressive therapy is the potential for these agents to affect the nutrition status of the transplant recipient. Given the fact that many patients undergoing transplantation are catabolic and nutritionally vulnerable, it is particularly important for those involved in the care of these patients to be familiar with the nutrition implications of immunosuppressive drugs. In this article, we review the different classes of immunosuppressive medications used in transplantation and emphasize their interactions with the nutrition status of the transplant recipient.

Recent Treatment of Interstitial Lung Disease with Idiopathic Inflammatory Myopathies

Interstitial lung disease (ILD) is a prognostic factor for poor outcome in polymyositis (PM)/dermatomyositis (DM). The appropriate management of ILD is very important to improve the prognosis of patients with PM/DM. ILD activity and severity depend on the disease subtype. Therefore, clinicians should determine therapeutic strategies according to the disease subtype in each patient with PM/DM. Anti-melanoma differentiation-associated gene 5 antibody and hyperferritinemia predict the development and severity of rapidly progressive (RP) ILD, particularly in East Asian patients. Combination therapy with corticosteroids, intravenous cyclophosphamide pulse, and calcineurin inhibitors should be administered in RP-ILD. In contrast, patients with anti-aminoacyl-tRNA synthetase (ARS) show better responses to corticosteroids alone. However, ILDs with anti-ARS often display disease recurrence or become refractory to corticosteroid monotherapy. Recent studies have demonstrated that the administration of tacrolimus or rituximab in addition to corticosteroids may be considered in ILD patients with anti-ARS. Large-scale, multicenter randomized clinical trials should be conducted in the future to confirm that the aforementioned agents exhibit efficacy in ILD patients with PM/DM. The pathophysiology of ILD with PM/DM should also be elucidated in greater detail to develop effective therapeutic strategies for patients with ILD in PM/DM.

Cyclosporine use in hematopoietic stem cell transplantation: pharmacokinetic approach

Cyclosporine is one of the most vital agents in the process of successful allogeneic hematopoietic stem cell transplantation. Despite a long history and worldwide extent of cyclosporine use for prevention of graft versus host disease, currently there are lots of uncertainties about its optimal method of application to reach the best clinical outcome. A major portion of this problem stems from complicated cyclosporine pharmacokinetics. Study of cyclosporine pharmacokinetic behavior can significantly help recognition of its effectiveness and consequently, optimization of dosing, administration, monitoring and management of adverse effects. In this review, highly accredited but sparse scientific data are gathered in order to provide a better insight for preparation of practice guidelines and directing future studies for allogeneic hematopoietic cell recipients.

Therapeutic drug monitoring in pediatric renal transplantation

Finding the balance between clinical efficacy and toxicity of immunosuppressive drugs is a challenge in renal transplantation (RTx), but especially in pediatric RTx patients. Due to the expected longer life-span of pediatric transplant patients and the long-term consequences of drug-induced infectious, malignant and cardiovascular adverse effects, protocols which minimize immunosuppressive therapy make conceptual sense. In this context, therapeutic drug monitoring is a tool which provides support for the individualization of therapy. It has, however, limitations, and specific data in the pediatric cohort are comparatively sparse. There is large heterogeneity among the studies conducted to date in terms of methods, follow-up, endpoints, immunosuppressive regimens and patients. In addition, data from adult studies are not readily transferrable to the pediatric situation. This educational review gives a concise overview on aspects of therapeutic drug monitoring in pediatric RTx.

Lack of drug interaction between cyclosporine and telaprevir in a liver transplant recipient

Telaprevir is a novel NS3A/4A protease inhibitor approved in combination with ribavirin and peg-interferon alfa for the treatment of genotype-1 chronic hepatitis C. This drug is also known to be a potent cytochrome P450 3A and drug efflux protein ATP-binding cassette B1 (also called P-glycoprotein) inhibitor, and could therefore interact with immunosuppressive drugs. For this reason, a decrease in cyclosporine (CsA) dosage has been proposed when combining this drug with telaprevir. We report herein the case of an unpredictable lack of interaction between CsA and telaprevir in a liver transplant recipient. The decrease in CsA dosage, conducted as recommended in the literature, did not result in stable CsA concentrations but decreased them. However, the decrease in CsA exposure could have been unseen without the measurement of CsA concentrations 2 h after the administration (C2 ) of the drug, because it mainly resulted from the decrease in CsA peak. The mechanism leading to this lack of drug interaction in this patient has not been fully elucidated yet, but is likely to affect the absorption phase. Therapeutic drug monitoring using only CsA trough concentrations could be falsely reassuring, and the addition of the measurement of the C2 may add useful information to adapt CsA dosage in patients co-treated with telaprevir.

High intra-individual variability of cyclosporine pharmacokinetics in lung transplant recipients without cystic fibrosis

BACKGROUND

There has been little study on the variability of CsA pharmacokinetics in stable lung transplant (LT) recipients without cystic fibrosis. This study was conducted to determine the prevalence of high intra-individual variability of CsA in LT recipients and its implications in CsA monitoring.

METHODS

Twenty-nine pharmacokinetic curves were performed in 10 consecutive stable patients from a single center. The intra-individual coefficient of variation (CV) of the AUC₀₋₁₂ h was calculated in each case. Patients were grouped according to whether their CV was high (≥20%) or low (<20%). Correlations between cyclosporine CsA concentration at each time point, AUC₀₋₄ h , and AUC₀₋₁₂ h were also calculated.

RESULTS

Six (60%) patients presented low CVs and four (40%) high CVs. In patients with low CVs, the best correlation of AUC₀₋₁₂ h was with CsA concentration at two h post-dose (C₂) (r = 0.674, p = 0.002), whereas in those with high CV, the best correlation was with C5 (r = 0.800, p = 0.003). In the latter group, the correlation with C₂ was low (r = 0.327, p = 0.32), whereas the correlation with C₀ was high (r = 0.709, p < 0.05).

CONCLUSIONS

Intra-individual variability of CsA pharmacokinetics may be high in many LT recipients. In patients with high CV, the use of C₀ levels may be more appropriate for CsA monitoring than C₂ levels.

Pre-treatment ferritin level and alveolar-arterial oxygen gradient can predict mortality rate due to acute/subacute interstitial pneumonia in dermatomyositis treated by cyclosporine a/glucocorticosteroid combination therapy: a case control study [corrected]

BACKGROUND

Acute/subacute interstitial pneumonia in dermatomyositis (DM-A/SIP) is a disease associated with a poor prognosis that resists treatment with glucocorticosteroids (GC) and progresses rapidly in a period of weeks to months to death. We retrospectively studied outcomes, prognostic factors, and their relations with survival rate in patients with DM-A/SIP treated with early cyclosporine A (CSA)/GC combination therapy and 2-hour postdose blood concentration monitoring.

METHODS

This study comprised 32 DM-A/SIP patients who were simultaneously treated with CSA and prednisolone. Clinical and laboratory findings were compared between those who died due to DM-A/SIP and those surviving 24 weeks after beginning of therapy. Prognostic factors were extracted, and their relations with the survival rate were evaluated.

RESULTS

Of the 32 DM-A/SIP patients, 25 survived, 5 died of DM-A/SIP, and 2 died of infections. In those who died due to DM-A/SIP, ferritin level and the alveolar-arterial oxygen gradient were significantly increased compared with the survivors (P<0.001 and P = 0.002, respectively). Multivariate analyses showed that ferritin and alveolar-arterial oxygen gradient were independent prognostic factors of poor outcome. The survival rate 24 weeks after beginning of treatment was significantly lower in those with a ferritin level of ≥ 600 ng/ml and alveolar-arterial oxygen gradient of ≥ 45 Torr (P<0.001 and P<0.001, respectively). All patients with both prognostic factors died, and the outcome was significantly poorer in these patients than in those with one or neither of the prognostic factors (P<0.001).

CONCLUSIONS

We identified pre-treatment high serum ferritin level and high alveolar-arterial oxygen gradient as poor prognostic factors in DM-A/SIP patients undergoing early CSA/GC combination therapy and showed that the outcomes were poor in patients with both factors.

Significance of combined cyclosporine-prednisolone therapy and cyclosporine blood concentration monitoring for idiopathic membranous nephropathy with steroid-resistant nephrotic syndrome: a randomized controlled multicenter trial

Background

Combined treatment with cyclosporine microemulsion preconcentrate (CyA MEPC) and steroids has been widely used for idiopathic membranous nephropathy (IMN) associated with steroid-resistant nephrotic syndrome (SRNS). Recent studies have shown that once-a-day and preprandial administration of CyA MEPC is more advantageous than the conventional twice-a-day administration in achieving the target blood CyA concentration at 2 h post dose (C2). We designed a randomized trial to compare these administrations.

Methods

IMN patients with SRNS (age 16–75 years) were divided prospectively and randomly into 2 groups. In group 1 (n = 23), 2–3 mg/kg body weight (BW) CyA MEPC was given orally once a day before breakfast. In group 2 (n = 25), 1.5 mg/kg BW CyA MEPC was given twice a day before meals. CyA + prednisolone was continued for 48 weeks.

Results

Group 1 showed a significantly higher cumulative complete remission (CR) rate (p = 0.0282), but not when incomplete remission 1 (ICR1; urine protein 0.3–1.0 g/day) was added (p = 0.314). Because a C2 of 600 ng/mL was determined as the best cut-off point, groups 1 and 2 were further divided into subgroups A (C2 ≥600 ng/mL) and B (C2 <600 ng/mL). Groups 1A and 2A revealed significantly higher cumulative remission (CR + ICR1) (p = 0.0069) and CR-alone (p = 0.0028) rates. On the other hand, 3 patients with high CyA levels (C2 >900 ng/mL) in Group 1A were withdrawn from the study because of complications.

Conclusion

CyA + prednisolone treatment is effective for IMN with associated SRNS at a C2 of ≥600 ng/mL. To achieve remission, preprandial once-a-day administration of CyA at 2–3 mg/kg BW may be the most appropriate option. However, we should adjust the dosage of CyA by therapeutic drug monitoring to avoid complications.

Endoplasmic reticulum stress with low-dose cyclosporine in frequently relapsing nephrotic syndrome

BACKGROUND

A possible mechanism of cyclosporine (CsA) nephrotoxicity is tubular apoptosis. Endoplasmic reticulum (ER) stress has been shown to be an apoptosis activator. Glucose-regulated proteins 78 and 94 (GRP78, GRP94, respectively) are ER stress-induced chaperones. Eukaryotic translation initiation factor 2α (EIF2α) attenuates protein synthesis. If stress is prolonged, cells undergo apoptosis, inducing the production of GADD153, a transcription factor, which in turn downregulates anti-apoptotic protein B-cell lymphoma 2 (Bcl-2).

METHODS

Endoplasmic reticulum stress-related molecules were evaluated by real-time polymerase chain reaction (PCR) using renal biopsy tissues from 17 children with frequently relapsing nephrotic syndrome before and after 2 years of CsA therapy.

RESULTS

GRP78, GRP94, eIF2α, and Bcl-2 were significantly upregulated in renal biopsy tissues from children 2 years post-CsA treatment. However, there was almost no change in GADD153. Mean ratios of post- to pre-CsA expression of GRP78, GRP94, eIF2α and Bcl-2 were 2.53, 1.80, 2.38 and 1.92, respectively. Post-CsA administration, GRP78 and eIF2α were upregulated by up to sixfold, and GRP94 and Bcl-2 were upregulated by up to fourfold compared with the respective pre-CsA levels. There were significant correlations between GRP78, GRP94, eIF2α, and Bcl-2 levels. These findings suggest that CsA induced an unfolded protein response due to ER stress, but did not cause apoptosis.

CONCLUSIONS

An unfolded protein response due to ER stress induced by CsA may function in a defensive manner, with less apoptosis occurring under low-dose conditions. This finding is important for the rationale for CsA administration.

Bronchiolitis obliterans syndrome: the Achilles' heel of lung transplantation

Lung transplantation is a therapeutic option for patients with end-stage pulmonary disorders. Unfortunately, chronic lung allograft dysfunction (CLAD), most commonly manifest as bronchiolitis obliterans syndrome (BOS), continues to be highly prevalent and is the major limitation to long-term survival. The pathogenesis of BOS is complex and involves alloimmune and nonalloimmune pathways. Clinically, BOS manifests as airway obstruction and dyspnea that are classically progressive and ultimately fatal; however, the course is highly variable, and distinguishable phenotypes may exist. There are few controlled studies assessing treatment efficacy, but only a minority of patients respond to current treatment modalities. Ultimately, preventive strategies may prove more effective at prolonging survival after lung transplantation, but their remains considerable debate and little data regarding the best strategies to prevent BOS. A better understanding of the risk factors and their relationship to the pathological mechanisms of chronic lung allograft rejection should lead to better pharmacological targets to prevent or treat this syndrome.

Prediction of area under the cyclosporine concentration versus time curve in children undergoing hematopoietic stem cell transplantation

This prospective study aimed to validate a previously developed first-dose limited sampling strategy (LSS) to predict the area under the cyclosporine concentration-versus-time curve (AUC) and to develop and then validate an LSS to predict cyclosporine AUC at steady state. This two-center Canadian study included children (ages .4 to 17.2 years) undergoing myeloablative allogeneic hematopoietic stem cell transplantation receiving cyclosporine for acute graft-versus-host disease prophylaxis. There were three cohorts, each incorporating 24 AUC determinations: first-dose LSS validation, steady-state LSS development, and steady-state LSS validation. Patients contributing data to either of the development cohorts were excluded from the corresponding validation group. Cyclosporine was given every 12 hours as a 2-hour infusion. Cyclosporine AUC was determined after administration of the first cyclosporine dose (8 samples) and then once weekly (9 samples) until engraftment. Steady-state LSSs were developed using stepwise multiple linear regression. An LSS was considered to provide an acceptable estimate of AUC if the lower limit of the 95% confidence limit (CL) of the intraclass coefficient was .8 or higher and both bias and precision were 15% or less. Fifty-three children age .4 to 18 years participated. Cyclosporine concentrations drawn up to 4 hours from the start of the infusion correlated most strongly with AUC. The previously developed first-dose LSSs and three steady-state LSSs met criteria for acceptability. The intraclass coefficients of the three-point first-dose LSS validation cohort, three-point steady-state LSS development cohort, and three-point steady-state LSS validation cohort were .974 (95% CL: .941 to .988), .984 (95% CL: .965 to .993), and .993 (95% CL: .984 to .997), respectively. The three-point first-dose (2, 6, and 8 hours) and steady-state (2, 2.5, and 8 hours) LSSs are valid measures of cyclosporine AUC after intravenous administration over 2 hours. Their use in a prospective evaluation of the relationship between cyclosporine AUC and hematopoietic stem cell transplantation clinical outcomes in children is suggested.

Acute effects of calcineurin inhibitors on kidney allograft microperfusion visualized by contrast-enhanced sonography

BACKGROUND

Calcineurin inhibitors induce detrimental vascular remodeling, which may be one cause of chronic allograft failure. Real-time contrast-enhanced sonography (CES) is a relatively new technique in providing quantitative information on microvascular tissue perfusion in kidney allografts in more detail. The purpose of the study was to explore whether acute changes of kidney allograft microperfusion due to the administration of cyclosporine A (CsA) and tacrolimus (Tac) can be evidenced using real-time CES.

METHODS

In an explorative single-center clinical trial, renal parenchymal tissue perfusion of 32 stable kidney allograft recipients was evaluated with CES before and 2 hr after the intake of CsA or Tac. In addition to laboratory and clinical parameters, Doppler indices and estimated glomerular filtration rate were measured.

RESULTS

Although systolic and diastolic blood pressure and color Doppler indices did not significantly differ, there was a significant decrease of renal blood flow 2 hr after the intake of CsA compared with baseline (4.78±2.31 dB/s, 49%, respectively). In contrast, kidney allograft microperfusion was neither significantly reduced in patients receiving CsA paralleled by calcium channel blockers nor significantly reduced in patients receiving Tac. Furthermore, there was a significant correlation between renal blood flow obtained before drug administration and kidney function.

CONCLUSIONS

CES revealed a 49% reduction of kidney allograft microperfusion 2 hr after the intake of CsA, which might be abrogated by calcium channel blockers. In comparison to CsA, Tac did not result in a significant decrease of kidney blood flow.

Population pharmacokinetics of ciclosporin in haematopoietic allogeneic stem cell transplantation with emphasis on limited sampling strategy

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • The population pharmacokinetics and limited sampling strategies for ciclosporin monitoring have been extensively studied in renal and liver transplant recipients. Little is known about the pharmacokinetics of ciclosporin in patients undergoing haematopoietic allogeneic stem cell transplantation (HSCT). • It is anticipated that there is a difference in pharmacokinetics in patients after kidney or liver transplantation compared with patients undergoing stem cell transplantation, because of mucositis and interacting drugs (e.g. fluconazole). • Data on the pharmacokinetics of ciclosporin and the relationship between its systemic exposure, as reflected by the area under the curve (AUC), and the biological effect as graft vs. host-disease (GVHD) prophylaxis and graft vs. tumour (GVT) response are scarce in patients after HSCT. WHAT THIS STUDY ADDS • A pharmacokinetic model was developed for orally and intravenously administered ciclosporin, enabling an adequate estimate of the systemic exposure of ciclosporin in patients after HSCT. A limited sampling strategy was tested that may serve as a tool to study the optimum systemic exposure (AUC) of ciclosporin in HSCT to prevent GVHD but establish adequate GVT response and to guide therapeutic drug monitoring. AIM To develop a population pharmacokinetic model of ciclosporin (CsA) in haematopoietic allogeneic stem cell transplantation to facilitate a limited sampling strategy to determine systemic exposure (area under the curve [AUC]), in order to optimize CsA therapy in this patient population. METHODS The pharmacokinetics of CsA were investigated prospectively in 20 patients following allogeneic haematopoietic stem cell transplantation (HSCT). CsA was given twice daily, as a 3 h i.v. infusion starting at day 1 of the conditioning scheme, and orally later on, when oral intake was well tolerated. Fluconazole was given as antimycotic prophylaxis. Pharmacokinetic parameter estimation was performed using nonlinear mixed effect modelling as implemented in the NONMEM program. A first order absorption model with lag time was compared with Erlang frequency distribution and Weibull distribution models. The influence of demographic variables on the individual empirical Bayesian estimates of clearance and distribution volume was tested. Subsequently two limited sampling strategies (LSS) were evaluated: posterior Bayesian fitting and limited sampling equations. RESULTS Twenty patients were included and 435 samples were collected after i.v. and oral administration of CsA. A two compartment model with first order absorption best described the data. Clearance (CL) was 21.9 l h(-1) (relative standard deviation [RSD]± 5.2%) with an inter-individual variability of 21%. The central volume of distribution (V(c) ) was 18.3 l (RSD ± 8.7%) with an inter-individual variability of 29%. Bioavailability (F) was 0.71 (RSD ± 9.9%) with and inter-individual variability of 25% and lag time (t(lag) ) was 0.44 h (RSD 5.5%). Weight, body surface area, haematocrit, albumin, ALAT and ASAT had no significant influence on pharmacokinetic parameters. The best multiple point combination for posterior Bayesian fitting, in terms of estimating systemic CsA exposure, appeared to be C0 + C2 + C3. Two selected LSS two time point equations and all selected three and four time point equations predicted de all AUC(0,12 h) within 15% bias and prediction. CONCLUSIONS The i.v. and oralcurves were best described with a two compartment model with first-order absorption with lag time. With the Bayesian estimators from this model, the area under the concentration-time curve in HSCT patients taking fluconazole can be estimated with only three blood samples (0, 2, 3 h) with a bias of 1% and precision of 4%.

Age effect on whole blood cyclosporine concentrations following oral administration in children with nephrotic syndrome

The aim of this study was to investigate age-related pharmacokinetic differences of cyclosporine (CyA) in children with nephrotic syndrome. Whole blood concentrations of CyA were monitored for a total of 96 times in 36 cases. The 25 male and 11 female patients ranged in age from 1.9 to 19.7 years with a mean age of 9.1 years. Renal biopsy showed minimal change in 33 patients and focal segmental glomerulosclerosis in three patients. CyA was orally administered in two divided doses just before meals. The doses of CyA administered were adjusted such that the target value for blood concentration at 2 h post-dose (C2) was 400-450 ng/ml. The 96 subjects were divided into three groups according to age: group I, 1-5 years (n = 30); group II, 6-10 years (n = 34); and group III, ≥ 11 years (n = 32). In all subjects, peak levels (Cmax) of CyA were reached at C1 or C2. There was no significant difference between the groups for C2, area under the whole blood concentration-time curve up to 4 h post-dose (AUC0-4), and Cmax. The mean CyA doses of groups I, II, and III were 4.8 ± 1.0 mg/kg/day, 3.8 ± 0.9 mg/kg/day, and 3.0 ± 0.6 mg/kg/day, respectively, and there were significant differences between every two groups. In addition, the dose-normalized Cmax (Cmax/dose) and AUC0-4 (AUC0-4/dose) values were significantly lower in the younger group than in the older group. These findings suggested that in children, when the same concentration is targeted, the required CyA dose would vary according to age but would be significantly higher for the younger children.

Conventional and novel approaches to immunosuppression

Immunosuppressive therapy has contributed significantly to improved survival after solid organ transplantation. Nevertheless, treatment-related adverse events and persistently high risk of chronic graft rejection remain major obstacles to long-term survival after lung transplantation. The development of new agents, refinements in techniques to monitor immunosuppression, and enhanced understanding of transplant immunobiology are essential for further improvements in outcome. In this article, conventional immunosuppressive regimens, novel approaches to preventing graft rejection, and investigational agents for solid organ transplantation are reviewed.

Predictive factors for ciclosporin-associated nephrotoxicity in children with minimal change nephrotic syndrome

Aims

To identify the predictive factors for ciclosporin A (CyA)-associated nephrotoxicity (CAN) in children with minimal change nephrotic syndrome (MCNS).

Methods

The clinical and laboratory findings of 58 children (median age 3.2 years, range 1.1–13.1 years, male:female 48:10) with MCNS who were treated with CyA from 1992 to 2002 were analysed retrospectively. Forty-eight (83%) of them were steroid dependent and 10 (17%) were steroid resistant. The starting dose of CyA was 5 mg/kg per day, and the desired drug level was kept at 100–200 ng/ml. Serial renal biopsies were performed before and after CyA therapy.

Results

Twenty-two patients (38%) had CAN (group I) and 36 (62%) did not (group II). There were no differences in the age at onset, sex, initial response to steroids, duration of CyA therapy and relapse rates. However, the median CyA trough levels were significantly higher in group I than in group II (218.0±15.2 vs 171.8±6.7 ng/ml, p=0.01). Changes in creatinine clearance were more decreased in group I than in group II (−39.4±8.2 vs 2.7±4.3 ml/min per 1.73 m2, p<0.0001). Multiple logistic regression analysis also revealed the median CyA trough level was an independent risk factor for the development of CAN (OR 1.025, 95% CI 1.007 to 1.044, p=0.007).

Conclusions

The median CyA trough level was an independent and significant risk factor for the development of CAN in children with MCNS receiving moderate-dose CyA.

Liquid chromatography-tandem mass spectrometry method for simultaneous determination of cyclosporine A and its three metabolites AM1, AM9 and AM4N in whole blood and isolated lymphocytes in renal transplant patients

A LC-MS/MS method was developed and validated for the determination of cyclosporine A (CsA) and its three phase 1 metabolites AM1, AM9, and AM4N in whole blood and lymphocytes isolated on the Histopaque gradient. 200 microL of whole blood was precipitated with 10 mol/L zinc sulfate in acetonitrile/methanol (40:60, v/v) and lymphocytes isolated from 1.5 mL blood were extracted with acetonitrile/methanol (40:60, v/v). The analytes and internal standard cyclosporine D were separated on RP column BEH C18, 2.1 x 50 mm, 1.7 microm using gradient LC-MS/MS analysis in positive electrospray mode. Time of analysis was 5 min. Linearity in blood was 5-2000 microg/L for CsA, AM1, and AM9; 2-500 microg/L for AM4N; and 2-500 microg/L for all substances in lymphocytes. Coefficient of variations was 1.8-9.8% and recovery was 92.0-110.0%. The method was used in early and chronic renal transplant patients for therapeutic drug monitoring of CsA to compare either its share in lymphocytes as target organ or binding to one lymphocyte. The same parameters were calculated for all metabolites tested.

Therapeutic drug monitoring of cyclosporine microemulsion in interstitial pneumonia with dermatomyositis

The prognosis of dermatomyositis (DM)-associated progressive interstitial pneumonia (IP) has recently been improved by steroids/cyclosporine-A (CSA) combination therapy, but treatment outcomes varied. One reason for this variation is thought to be differences in CSA regimen. There is marked interpatient variability in CSA absorption. However, the pharmacokinetics of CSA has rarely been studied. In this study, we calculated the area under the blood concentration-time curve (AUC) of CSA microemulsion in 15 patients with progressive IP complicating DM, and analyzed its correlation with CSA levels at blood sampling time points to investigate the optimum monitoring and dosing regimen. The highest correlation between AUC(0-6) and blood level of CSA was observed 2 h (C2) after drug administration (R = 0.910). The trough level (C0) was not correlated with AUC(0-6) (R = 0.052). There were no differences in blood levels (AUC(0-6), C2, and C6) between postprandial administration in a divided dose (CSA given twice daily) and preprandial administration once daily in a single dose, while C0 was significantly lower (P = 0.020) when the drug was administered once daily before breakfast. These findings suggest that measurement of CSA blood level, especially C2 and C0, is useful to monitor clinical and adverse effects of CSA during combination therapy. It is also suggested that preprandial, once daily administration of CSA is beneficial in DM patients with progressive IP.

Optimizing post-transplant outcomes in lung transplantation

Lung transplant recipients are at risk of numerous complications, which range from early events, such as primary graft dysfunction, to late events, including opportunistic infection or graft loss caused by chronic rejection. Although lung transplantation is often the only therapeutic option that can improve quality of life and prolong survival for many forms of end-stage lung disease, survival following lung transplantation is significantly worse than survival following transplantation of other solid organs. Carefully choosing potential recipients for listing, maximizing the likelihood that donor organs will function well following implantation, appropriate use of immunosuppressive agents to prevent allograft rejection, prophylactic or pre-emptive strategies to prevent allograft infection and appropriate surveillance to detect significant complications are key to maximizing the likelihood of prolonged graft and patient survival while avoiding significant complications following lung transplantation. Post-transplant outcomes will be optimized by a team approach to comprehensive management of the lung transplantation recipient combined with vigilant surveillance to detect complications in a timely fashion.

Individualized Neoral doses in pediatric renal transplantation

We propose a model to calculate individualized Neoral doses based on individual oral clearance (CL/F)(i) and AUC((0-12h)) values. The equation proposed by Dr. Ke-Hua Wu (2005), was employed to calculate the CL/F(i) = 28,5 - (1.24*POD) - 0.252*(TBil-11) + 0,188*(Weight o-58) -0,191*(Age-42) - 2,42*INHI - 0,212*(HCT-28), where CI/F = (L/h), POD = postoperative days, Bil.T = total bilirubin level (umol/L), CBW = in kilograms, age = in years, INHI = concurrent metabolic inhibitors present (1) or absence (0), and HCT = hematocrit percentage. The AUC((0-12h)) was calculated from the C(2) value using the equation AUC((0-12h)) = 815,578 + 4,44696*C(2), derived from the linear correlation observed in earlier work at Clinica Las Condes Hospital. The studied population were 30 kidney transplanted children at Luis Calvo Mackenna Hospital, between 2002 and 2006, who were divided into 2 similar groups according to accurate C(2) sampling time collections. The control group 1 was composed of 13 patients of age 9.85 +/- 4 years whose samples were collected correctly. Group 2 was composed of 17 patients of age 10.43 +/- 6 years with 252 C(2) samples, which were obtained at medical control. All patients were under oral treatment with prednisone, azathioprine, nifedipine, and Neoral administered twice day according the weight of the patient and the C(2) level. Relating Neoral administered doses to calculated doses according to the proposed model, the control group showed a linear correlation coefficient r = 0.924; r(2) = 85.4%; (P < .05), and group 2, r = 0.54; r(2) = 29.1 (P < .05). The proposed model to calculate Neoral doses had a predictive value of 85.0% when C(2) samples were collected correctly.

Steroid avoidance using sirolimus and cyclosporine in pediatric renal transplantation: one year analysis

Steroids are commonly used in pediatric renal transplantation, but have numerous adverse effects. This retrospective study compares one-yr outcomes in 22 pediatric renal transplant recipients receiving SRL and CSA as primary immunosuppression (steroid-avoidance group) to age- and gender-matched historical controls receiving CSA, MMF, and prednisone (steroid group). At one yr, both groups had similar graft survival, acute rejection, and estimated GFR. Subjects in the steroid-avoidance group had better linear growth, less excessive weight gain and were less likely to have an increase in antihypertensive medication use. Subjects in the steroid-avoidance group were more likely to be started on lipid lowering medications and erythropoiesis stimulating agents. Despite having a greater proportion of living donors, the steroid-avoidance group had a similar GFR compared to the steroid group at one month. The steroid-avoidance group was also more likely to have a biopsy for elevated Cr that was not because of rejection and had more interstitial fibrosis noted. We conclude that using a steroid-avoidance immunosuppression regimen of SRL and CSA results in comparable rejection rates and short-term graft function with less steroid-associated morbidity. However, early findings also suggest possible potentiation of CSA nephrotoxicity by SRL in some children.

Pharmacogenetics of calcineurin inhibitors in renal transplantation

Cyclosporine A and tacrolimus (Tac) are inmunosuppresive drugs with a narrow therapeutic range. Underdosing is associated with organ rejection, whereas overdosing could result in toxicity. Therapeutic drug monitoring at different postdose times is necessary to maintain the blood concentrations within a target window. These calcineurin inhibitors are characterized by a broad interindividual pharmacokinetics variability, which makes the determination of the initial dose difficult. In a patient receiving a dose, the amount of the drug that is measured in the blood determines its bioavailability, which depends on the absorption, biotransformation, and elimination of the drug. These processes are primarily controlled by efflux pumps and enzymes of the cytochrome P (CYP) 450 family. DNA variants at the genes encoding these proteins contribute to the interindividual heterogeneity for calcineurin inhibitors metabolism. Cyclosporine A and Tac are metabolized by CYP3A4 and CYP3A5, and several single nucleotide polymorphisms in the two genes have been associated with differences in drug clearance. Carriers of the CYP3A5 wild-type allele have a higher CYP3A5 expression compared with individuals who are homozygous for a common DNA variant that affects gene splicing (CYP3A5*3). For renal transplant recipients receiving Tac, homozygotes for this nonexpression allele would exhibit significantly lower Tac clearance and may require a lower dose to remain within the blood target concentration compared with CYP3A5 expressors. To date, this CYP3A5 variant is the only reported genetic factor to predict the appropiate starting dosage of Tac, avoiding overdosing and improving the outcome of renal transplantation.