Improved absorption of cyclosporin A from a new microemulsion formulation: implications for dosage and monitoring

[From the first kidney transplants to the current pediatric kidney transplant]

Kidney transplantation is the preferred treatment for end-stage renal failure in children but remains a rare procedure with only 100 to 120 pediatric kidney transplants per year in France. Although the main principles of kidney transplantation are the same in children and adults, some specificities regarding underlying kidney diseases, surgical technique, immunosuppressive drugs metabolism and the risk of infectious complications require a specific expertise to care for these patients. Similarly, the major morbidity of dialysis in children and the need for repeated transplants during the patient's life justify pediatric specificities in the choice of donors and the allocation of grafts in most kidney allocation systems worldwide. The objectives of this review are to present the history and specificities of pediatric kidney transplantation, to describe the current activity in France and to discuss future developments while emphasizing the need for basic and clinical research focused on the pediatric population.

Pearls and Pitfalls in Pediatric Kidney Transplantation After 5 Decades

Worldwide, over 1,300 pediatric kidney transplantations are performed every year. Since the first transplantation in 1959, healthcare has evolved dramatically. Pre-emptive transplantations with grafts from living donors have become more common. Despite a subsequent improvement in graft survival, there are still challenges to face. This study attempts to summarize how our understanding of pediatric kidney transplantation has developed and improved since its beginnings, whilst also highlighting those areas where future research should concentrate in order to help resolve as yet unanswered questions. Existing literature was compared to our own data of 411 single-center pediatric kidney transplantations between 1968 and 2020, in order to find discrepancies and allow identification of future challenges. Important issues for future care are innovations in immunosuppressive medication, improving medication adherence, careful donor selection with regard to characteristics of both donor and recipient, improvement of surgical techniques and increased attention for lower urinary tract dysfunction and voiding behavior in all patients.

Development of a Pediatric Relative Bioavailability/Bioequivalence Database and Identification of Putative Risk Factors Associated With Evaluation of Pediatric Oral Products

Generally, bioequivalence (BE) studies of drug products for pediatric patients are conducted in adults due to ethical reasons. Given the lack of direct BE assessment in pediatric populations, the aim of this work is to develop a database of BE and relative bioavailability (relative BA) studies conducted in pediatric populations and to enable the identification of risk factors associated with certain drug substances or products that may lead to failed BE or different pharmacokinetic (PK) parameters in relative BA studies in pediatrics. A literature search from 1965 to 2020 was conducted in PubMed, Cochrane Library, and Google Scholar to identify BE studies conducted in pediatric populations and relative BA studies conducted in pediatric populations. Overall, 79 studies covering 37 active pharmaceutical ingredients (APIs) were included in the database: 4 bioequivalence studies with data that passed BE evaluations; 2 studies showed bioinequivalence results; 34 relative BA studies showing comparable PK parameters, and 39 relative BA studies showing differences in PK parameters between test and reference products. Based on the above studies, common putative risk factors associated with differences in relative bioavailability (DRBA) in pediatric populations include age-related absorption effects, high inter-individual variability, and poor study design. A database containing 79 clinical studies on BE or relative BA in pediatrics has been developed. Putative risk factors associated with DRBA in pediatric populations are summarized.

Pediatric kidney transplantation: a historical review

Successful renal transplantation is the optimal treatment for chronic kidney failure, but this was not always so for children. Beginning with the first kidney transplants in the 1950s, children experienced poorer patient and graft survival rates than adult patients. But over the last 6 decades, an improved understanding of the immune system which has steered pediatric multi-center clinical/pharmacokinetic and mechanistic studies that have sculpted our immunosuppression with markedly better patient and graft survivals. In addition, uniquely pediatric issues related to growth, development, neurocognitive maturation, increased complications from primary viral infections, and comorbid congenital/inherited disorders, are now diagnosed and effectively managed in these children. Refined pretransplant preparation (vaccinations for preventable diseases, attention to cognitive delays, effective dialysis and nutrition) improved donor selection, and more potent immunosuppression have all contributed to enhanced outcomes. Similarly, improvements in pediatric surgical techniques, postoperative care and better antiviral prophylaxis have all shortened hospitalizations and reduced morbidity. Today pediatric kidney transplant outcomes are markedly improved and younger children today experience better long-term graft survival than adults! While difficult problems remain, we have made tremendous progress and anticipate even more advances in the future of pediatric kidney transplantation.

Development, optimization and in vitro evaluation of norcantharidin loadedself-nanoemulsifying drug delivery systems (NCTD-SNEDDS)

This study focused on developing a self-nanoemulsifying drug delivery system (SNEDDS) containing bioactive surfactants under an efficient screening approach for overcoming problems associated with the delivery of norcantharidin (NCTD), a high dose chemotherapy agent having pH dependent solubility. Preliminary screening was implemented to select proper components combination. Besides the solubility of NCTD in the oil phase, emulsifying efficiency, droplet size and size distribution were also employed to select components of the SNEDDS. Moreover, the influence of surfactant and co-surfactant on the interfacial tension and droplets of nanoemulsions were investigated to further understand the mechanism of spontaneous emulsification. Co-surfactant addition promoted the emulsification via reducing the water/oil interfacial tension and viscosity. Ternary phase diagrams were constructed to investigate the phase behavior and designate the optimum systems. The alternative formulations were characterized for cloud point, dilution robustness, droplet size, polydispersity index (PDI) and transmission electron microscopy (TEM). In vitro dissolution study showed that the dissolution rate of optimized formulation (NCTD 10 mg/g, EO 50 wt.%, Cremophor EL 35 wt.%, ethylene glycol 15 wt.%) was slower than drug suspension under the same conditions, confirming that the developed SNEDDS formulation would exhibit sustained release potential.

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.

Developmental pharmacogenetics of immunosuppressants in pediatric organ transplantation

Cyclosporine, tacrolimus, sirolimus, and mycophenolate mofetil are the primary immunosuppressants used on pediatric organ transplantation. Therapeutic drug monitoring is used in daily practice, because their clinical use is hampered by a narrow therapeutic index and large variability. Tailoring immunosuppressive therapy to the individual patient to optimize efficacy and minimize toxicity is therefore essential. Because research in pharmacogenetics already identified polymorphisms impacting their pharmacokinetic parameters in adults, developmental pharmacogenetics of immunosuppressants holds promises for optimizing dosage regimens and improving clinical outcome in children. In this review, we focus on the impact of age and pharmacogenetics on these immunosuppressants in children undergoing organ transplantation.

Effect of cyclosporine therapy with low doses of corticosteroids on idiopathic nephrotic syndrome

Cyclosporine (CyA) has an immunosuppressive effect that might suggest a therapeutic role in idiopathic glomerular conditions. We focused on the optimization of CyA treatment control in patients with idiopathic nephrotic syndrome by using trough-level CyA measurements (C0) and the 2-h postdose levels (C2). Twenty-two patients (14 male, 8 female) with idiopathic nephrotic syndrome and the mean age of 51 +/- 18 months (mean [M] +/- standard deviation [SD]) were enrolled in our study during a period of 10 months (range: 3-18 months). All of the patients received CyA (2-3 mg/kg) in combination with methylprednisolone. In the present study protocol CyA concentrations (C0, C2), renal function, lipid profile, and degree of proteinuria were determined. The mean proteinuria of our patients before treatment was 11 972 +/- 7953 mg/24 H (+/-SD) and the mean creatinine level (Cr) was 0.99 +/- 0.37 mg/dL (+/-SD). Proteinuria decreased significantly already from the first month of therapy with CyA to 3578 +/- 2470 mg/24 H (M+/- SD), and during the whole study period this reduction was significant (0.56 +/- 0.37 gr/24 H (M +/- SD), P < 0.05). At the same time renal function preserved, 1.09 +/- 0.48 mg/dL (M +/- SD). The blood levels of C0 were 135.10 +/- 97.36 ng/mL (M +/- SD) and the blood levels of C2 were 725 +/- 256 ng/mL (M +/- SD) at the first month of therapy. At the same time renal function preserved, 1.09 +/- 0.48 mg/dL (M +/- SD). Total cholesterol levels reduced significantly during study period (276.89 +/- 45.57 to 200.67 +/- 40.27 mg/dL [M +/- SD]). The mean number of antihypertensive medication remained the same. The whole therapeutic protocol did not provoke any kind of side effects and CyA was quite tolerated by our patients. Treatment of idiopathic nephrotic syndrome with low doses of CyA with methylprednisolone leads to remission of proteinuria without deterioration of renal function. Blood levels of C0 for monitoring and treatment of nephrotic syndrome agrees with recent literature, while our study focus on establishing the proper levels of C2 for the treatment of nephrotic syndrome. The efficacy of CyA is combined with safety and tolerance.

Calcineurin inhibitors in pediatric renal transplant recipients

The calcineurin inhibitors, cyclosporine (ciclosporin) [microemulsion] and tacrolimus, are the principal immunosuppressants prescribed for adult and pediatric renal transplantation. For pediatric patients, both drugs should be dosed per body surface area, and pharmacokinetic monitoring is mandatory. While monitoring of the trough levels may suffice for tacrolimus, cyclosporine therapy that utilizes the microemulsion formulation requires additional monitoring (e.g. determination of 2-hour post-dose levels). In a well designed randomized study in children, as in studies in adults, there was no difference in short-term patient and graft survival with cyclosporine microemulsion and tacrolimus. However, tacrolimus was significantly more effective than cyclosporine microemulsion in preventing acute rejection after renal transplantation when used in conjunction with azathioprine and corticosteroids. With regard to long-term outcome, the difference in acute rejection episodes resulted in a better glomerular filtration rate at 1 year after transplantation and eventually in better graft survival 4 years after renal transplantation. Whether this difference persists when calcineurin inhibitors are used in combination with mycophenolate mofetil has not been determined. The prevalence of hypomagnesemia was higher in the tacrolimus group whereas hypertrichosis and gingival hyperplasia occurred more frequently in the cyclosporine group. In contrast with adults, the incidence of post-transplantation diabetes mellitus was not significantly different between tacrolimus- and cyclosporine-treated patients. There was also no difference with regard to post-transplantation lymphoproliferative disorder. Medication costs were similar, but in view of the lower rejection episodes and better long-term graft survival as well as the more favorable cosmetic side effect profile, tacrolimus may be preferable. The recommendation drawn from the available data is that both cyclosporine and tacrolimus can be used safely and effectively in children. We recommend that cyclosporine should be chosen when patients experience tacrolimus-related adverse events.

Evaluation of performance factors affecting two formulations of cyclosporine in pediatric renal transplant patients

Success of renal transplantation in children is largely due to improvements in immunosuppressant therapy since the introduction of calcineurin inhibitors. The aim of this study was to identify possible factors that result in formulation differences in the exposure of pediatric patients to cyclosporine (CsA). We examined the handling of the two major formulations of CsA in a group of pediatric renal transplant recipients. The pharmacokinetic profiles of both formulations were assessed, and the data stratified to assess the effects of age, gender, time posttransplant, and other concomitant drug therapy on the two CsA formulations. The microemulsified formulation (MEC) enhanced bioavailability compared to the older oil-based formulation (CYA), especially at C2, with more predictable and consistent absorption in children. This higher bioavailability allowed a 15% reduction of dosing to achieve equal drug exposure. The concentration achieved by MEC at C2 demonstrated a much higher correlation with area under the concentration curve (AUC) than the concentration at C0. In the case of CYA a strong correlation was obtained between AUC and the concentrations obtained at both C0 and C2. Calcium channel blockers increased AUC(0-8) for both CsA formulations. Norfloxacin and pravastatin cotreatment had no effect on either of the CsA formulations. In contrast, the bioavailability of CsA was increased in boys using MEC formulation but this gender-based difference was absent during the use of CYA. This suggests that caution is required for introduction of new formulations of drugs to pediatric patients to evaluate differential effects of age, gender, and concomitant drug therapy.

Disposition of two oral formulations of cyclosporine in pediatric patients receiving hematopoietic stem cell transplants

STUDY OBJECTIVES

To compare the disposition of cyclosporine after the administration of two oral formulations to children undergoing hematopoietic stem cell transplantation, and to evaluate the relationship between whole blood cyclosporine concentrations during the dosing interval and the area under the whole blood concentration-time curve.

DESIGN

Prospective, descriptive, crossover study.Setting. Hematopoietic stem cell transplantation unit in a tertiary-quaternary university-affiliated pediatric hospital.

PATIENTS

Twenty-four pediatric patients aged 0.5-16.9 years undergoing allogeneic hematopoietic stem cell transplantation.

INTERVENTION

The modified oral formulation of cyclosporine was given on the first day (divided as two doses), and a single identical dose of the original oral formulation was given on the morning of the second day.

MEASUREMENTS AND MAIN RESULTS

Blood samples were obtained at 0, 0.5, 1.25, 2, 4, 6, 9, and 12 hours after the morning dose from the lumen of the central venous catheter not previously used for intravenous cyclosporine administration. Cyclosporine concentration-time data were analyzed by using noncompartmental methods. Mean +/- SD maximum concentrations were significantly higher after administration of the modified form than after administration of the original form (594.9 +/- 349.7 vs 483.0 +/- 363.0 microg/L, p=0.003), as was the area under the concentration-time curve from 0-12 hours (AUC0-12; 3432 +/- 1563 vs 3144 +/- 1780 microg/L x hr, p=0.022). For both formulations, cyclosporine concentrations at 4 hours after administration were most strongly correlated with the AUC0-12. Unlike that of the original formulation, the trough cyclosporine concentration of the modified form had the weakest relationship with AUC (Spearman rho coefficient 0.584, p=0.003).

CONCLUSION

Cyclosporine absorption is lower in children undergoing hematopoietic stem cell transplantation than in children receiving solid organ transplants. Dosage adjustment for the modified formulation based on trough concentration may not be appropriate because its relationship with the AUC was weak. The link between pharmacokinetic parameters and clinical outcomes, such as graft-versus-host disease, must be further studied.

Cyclosporine A monitoring--how to account for twice and three times daily dosing

Cyclosporine A (CsA) dose-interval pharmacokinetic profiles, performed 1-4 years post-transplantation, were collected from 74 renal transplanted children. Forty patients were on three times daily dosing (t.i.d.) and 34 on twice daily dosing (b.i.d.). Regression models for prediction of area under the curve (AUC) using 1-3 concentration time points as independent variables were developed. With similar weight-adjusted single doses (mg kg(-1)) of CsA, t.i.d. dosing resulted in a trough-concentration (C0) similar to that from b.i.d. dosing, but a 30% lower 2 h post-dose concentration (C2). For b.i.d. dosing the relationship between C0 and AUC was poor (r2=0.23) and the prediction error was large (5.8+/-33.5%). For t.i.d. dosing the relationship was better (r2=0.79), but prediction error was still large (4.5+/-24.9%). For C2 relationships were similar to those for the b.i.d. (r2=0.59) and t.i.d. (r2=0.63) groups, but explained modestly the variations of AUC (prediction error=2.6+/-16.8% b.i.d., 4.8+/-23.2% t.i.d.). Both C0 and C2 are useful monitoring methods when CsA is administered t.i.d. If the aim is similar specified daily drug exposure, the target C2 should be roughly 30% smaller in t.i.d. dosing than in b.i.d. dosing and the target C0 could be similar. The prediction error of AUC can be large in individual patients when using single time-point determinations, however. The use of multiple time points reduces the variation, but is less feasible.

The impact of cyclosporine on the development of immunosuppressive therapy—pediatric transplantation using cyclosporine

Cyclosporine A (CsA) was introduced to pediatric renal transplantation more than 20 years ago, and it has greatly improved graft survival and made transplantation the treatment of choice for children with end-stage renal failure. Exposure to CsA was shown to be highly variable among transplant recipients. Therefore, major efforts have been employed to monitor CsA blood levels. The widely used trough levels had never been formally validated, and every center had defined its own target values. With the advanced microemulsion formula of CsA, drug exposure became more predictable, but scientifically evaluated monitoring concepts are still lacking. Monitoring the absorption phase using single time points (eg, 2 hours after ingestion) is promising, as shown in adult trials. In pediatric transplant recipients, randomized clinical trials have to be implemented urgently to fully exploit the potential of CsA in the prevention of graft rejection while minimizing toxicity. Although newer immunosuppressive drugs have been developed, further studies should be undertaken to define the role of CsA in combination protocols.

Cyclosporine in pediatric kidney transplantation

Before the era of cyclosporine (CsA), immunosuppression with azathioprine and steroids resulted in high rejection rates and severe growth retardation in pediatric renal transplant recipients. In the early 1980s, immunosuppression with CsA was introduced for children. Because of differences in metabolism rates and relation of weight and body surface area, special pediatric dosing regimens and monitoring strategies had to be developed. Use of CsA led to a decreased number of acute rejections and, consequently, to a marked increase in graft survival rates. The growth rates of transplanted children were significantly higher under CsA-based immunosuppression than with classical regimens. This was due to a decreased need of steroid co-administration. Main side effects of CsA in children were nephrotoxicity and hirsutism. The introduction of CsA microemulsion in the 1990s led to more reliable absorption profiles and to a lower interindividual variability of CsA area-under-the-curve concentrations and thus to another improvement in rejection rates. New monitoring strategies, based on CsA levels taken 2 hours' postdose, seem promising. In pediatric transplantation, CsA is often successfully combined with an antibody-induction therapy in order to reduce the number of early acute rejections. Combination with mycophenolate mofetil reduces the appearance of chronic rejection. Additional therapy with ToR inhibitors might enforce a reduction of CsA doses and therefore lead to a reduction of CsA toxic effects.

Immunosuppressive drugs in paediatric liver transplantation

Orthotopic liver transplantation is established treatment for children with acute and chronic liver failure. Despite advances in pre- and postoperative management, innovative surgical techniques and new immunosuppressive drugs, acute and chronic rejection remains a problem. In addition, well established adverse effects of commonly used immunosuppressive drugs are no longer accept able. More potent, but less toxic, immunosuppressive agents have been developed and some novel compounds are now entering routine practice. Cyclosporin was the cornerstone of immunosuppressive therapy until the introduction of its novel pharmaceutical form (Neoral) with improved bioavailability, lower inter- and intraindividual pharmacokinetic variability and improved graft survival. Recently, tacrolimus, a macrolide drug with a similar mode of action, but much higher potency, was introduced and, at present, is the only agent which can successfully replace cyclosporin as a first-line immunosuppressive drug. Mycophenolate mofetil has recently been approved for use in adult and paediatric renal transplant recipients. It has a similar mode of action to cyclosporin and tacrolimus, but acts at a later stage of the T cell activation pathway. Administration with standard immunosuppressive drugs reduces the incidence of acute rejection and enables cyclosporin and tacrolimus dose reduction, thus reducing the risk of associated toxic effects. Phase I and II trials with sirolimus (rapamycin), a macrolide antibiotic, have shown comparable immunosuppressive action, when administered in conjunction with standard immunosuppressants. Further clinical trials need to be carried out to establish efficacy, tolerability and pharmacokinetics in paediatric transplant recipients. Monoclonal antibody therapy (daclizumab and basiliximab) is an exciting new development whereby T cell proliferation is inhibited by selective blockade of interleukin (IL)-2 receptors. Preliminary results, when used in combination with a standard immunosuppressive regimen, are good with respect to incidence of acute graft rejection, host immune response and adverse effects. FTY720 is a novel synthetic immunosuppressive compound which induces a reduction in peripheral blood lymphocyte count through apoptotic T cell death or accelerated trafficking of T cells into lymphatic tissues. Experimental animal studies demonstrated synergistic action in combination with low dose cyclosporin or tacrolimus, potentiating their immunosuppressive effects. Further studies are being carried out to determine its potential for application in organ transplantation. Despite this rapid development of novel compounds, it will take many years before they may become part of standard protocols in paediatric transplantation medicine. Further development and research of efficacy and tolerability of existing drugs is, therefore, vital.

Recommendations for the outpatient surveillance of renal transplant recipients. American Society of Transplantation

Many complications after renal transplantation can be prevented if they are detected early. Guidelines have been developed for the prevention of diseases in the general population, but there are no comprehensive guidelines for the prevention of diseases and complications after renal transplantation. Therefore, the Clinical Practice Guidelines Committee of the American Society of Transplantation developed these guidelines to help physicians and other health care workers provide optimal care for renal transplant recipients. The guidelines are also intended to indirectly help patients receive the access to care that they need to ensure long-term allograft survival, by attempting to systematically define what that care encompasses. The guidelines are applicable to all adult and pediatric renal transplant recipients, and they cover the outpatient screening for and prevention of diseases and complications that commonly occur after renal transplantation. They do not cover the diagnosis and treatment of diseases and complications after they become manifest, and they do not cover the pretransplant evaluation of renal transplant candidates. The guidelines are comprehensive, but they do not pretend to cover every aspect of care. As much as possible, the guidelines are evidence-based, and each recommendation has been given a subjective grade to indicate the strength of evidence that supports the recommendation. It is hoped that these guidelines will provide a framework for additional discussion and research that will improve the care of renal transplant recipients.

Sandimmune to Neoral conversion and value of abbreviated AUC monitoring in stable pediatric kidney transplant recipients

Neoral is a new microemulsion formulation of cyclosporin A (CsA) that has been reported to have better absorption characteristics than sandimmune. We converted 25 long-term pediatric renal transplant recipients with a mean age of 14.1 yr and a mean follow-up period of 6.4 yr from sandimmune (SIM) to neoral (NEO) on a 1:1 basis. The mean dosage of SIM or NEO required to maintain 'therapeutic range' steady-state trough levels between 100 and 200 ng/mL was similar. We compared 6-h CsA pharmacokinetic profiles taken approximately 6 months after the conversion to NEO with the previous SIM profiles of the same patients. Generally, in the NEO profiles the time to reach the maximum concentration was shorter and the maximum concentration was higher, showing a rapid decline towards the trough-level when compared to the previous SIM profiles. During intake of NEO the AUC0-12 h in the 12-h profiles correlates strongly with the AUC0-6 h in the 6-h profiles (r = 0.98), a similar finding to that which we reported previously for SIM. The median AUC0-6 h for NEO demonstrates a 70% increase compared to the median AUC0-6 h for SIM. Despite the increased drug exposure NEO was well tolerated and did not cause any apparent toxicity within the first 6 months after conversion. The CsA blood level 2 h after intake of NEO showed a higher correlation with the AUC0-12 h (r = 0.91) than the trough level (r = 0.64). The abbreviated profile based on three early sampling points and calculated by AUCPRED = 335.9 + 1.1*(C1) + 1.1*(C2) + 5.4*(C4) correlated well with the full AUC (r2 = 0.98, p < 0.0001). Mean prediction error (+/- SD) was 0.16% (+/- 4.32), and in no patients did the calculated values fall outside the 10% prediction error limit. We therefore conclude that NEO exhibits a higher bioavailability in children compared to SIM without causing apparent toxicity. Monitoring of the C2 might be a better alternative for trough level monitoring in daily clinical practice. A strategy of three early sampling points (C1, C2 and C4) allows a reliable AUC0-12 h prediction and can reduce the length of observation, making it a useful and cost-effective tool in clinical practice.

Current and future modalities for functional renal replacement

Approximately 310,000 Americans suffer from end-stage renal disease, with more than 70,000 new cases reported each year. Advances in immunosuppressive therapy for transplanted patients, in addition to the refined care of patients who are dependent on dialysis, have led to an improved survival for patients with renal failure. Structural, molecular, and pharmacologic developments continue to enhance the efficacy and safety of dialysis in the future. In addition, progressive improvements in the past 2 decades in organ transplantation, a greater insight into the immunobiology of graft rejection, and better surgical and medical management have resulted in improved outcomes. Although renal xenotransplantation is still in its early stages of development, additional research is leading this technology forward. Recent successes in harvesting and expanding renal cells in vitro and the development of biologically active synthetic materials allow for the creation of three-dimensional functioning renal units, which, in the future, may be applied ex vivo or in vivo for partial or full replacement of kidney function.

Efficacy of Neoral in the immediate postoperative period in children post-liver transplantation

Cyclosporine (Sandimmune) is an effective immunosuppressive drug but may be poorly absorbed in the early postoperative period after liver transplantation, exposing the recipient to an increased risk for rejection. Neoral is a new oral formulation of cyclosporine that uses a mixture of surfactant, lipophilic, and hydrophilic solvents to permit microemulsification that leads to potentially better absorption. This oral drug has not been evaluated in children immediately posttransplantation. The aim of this study was to evaluate the pharmacokinetics, bioavailability, and safety of Neoral during the first week post-liver transplantation in children. Twelve children, 8 boys and 4 girls, with a median age of 2.6 years (range, 1 to 8 years) were administered Neoral within 12 hours posttransplantation. Pharmacokinetic profiles were performed over a 12-hour period on each child on days 1, 3, and 5 and twice-daily trough levels were obtained on days 2, 4, 6, and 7. The maximum concentration (Cmax), time to reach Cmax (Tmax), 12-hour trough levels, and area under the curve were calculated, and rejection episodes and adverse events were documented over a 12-week period. Neoral was well absorbed, even on the first postoperative day. After the introduction of enteral feeding, the peak levels increased (Cmax, 655 ng/mL) and were achieved significantly sooner (Tmax, 2 hours). There was no significant difference in drug exposure between days 1, 3, and 5 (P > .05). The incidence of acute rejection was 25% and hypertension was reported in 4 of 12 patients during the first week. Neoral was well absorbed in the early post-liver transplantation period, provided effective immunosuppression, and was not associated with a high incidence of adverse events or toxicity. The introduction of enteral feeding improved absorption.

A limited sampling strategy for the estimation of eight-hour neoral areas under the curve in renal transplantation

Neoral, the microemulsion formulation of cyclosporine (CsA), demonstrates more consistent bioavailability than the corn oil formulation Sandimmune. Because of Neoral's rapid peak and metabolism, 8-hour dosing has to be used in many pediatric and some adult patients to maintain adequate CsA peak-to-trough ratios. Although the area under the curve (AUC) is considered the best estimate of total drug exposure, it requires repeated blood sampling. Abbreviated AUC profiles yielding excellent estimates of Neoral AUC with twice daily dosing have been described, but no such abbreviated strategy exists for 8-hour dosing. One hundred fifty-two pharmacokinetic profiles in 23 patients were used to derive and prospectively test a limited two-sample strategy to predict Neoral AUCs in pediatric and adult patients on 8-hour dosing regimens of Neoral. The formula was derived from 69 full 8-hour CsA pharmacokinetic profiles in nine children who underwent renal transplantation. Stepwise forward linear and multiple-curve regression techniques assessed the relative importance of single and combination concentration time points to predict AUC. The abbreviated profiles were validated by comparing the mean prediction error for each regression equation. The abbreviated profile calculated by second (C2)- and fourth (C4)-hour levels (AUC = 129 + 1.84 x C2 + 4.39 x C4) correlated well with the full AUC (r2 = 0.96; p < 0001). Mean prediction error was -0.4% +/- 5.48%, and no values fell outside the clinically acceptable 15% prediction error limit. Prospectively applying the formula to 83 AUCs of 14 adults who underwent renal transplantation and were taking Neoral three times a day demonstrated an excellent fit (r2 = 0.93; p < 0.001), with 94% of predicted values falling inside the +/-15% limit. The authors describe the development of a clinically acceptable, limited sampling strategy to predict 8-hour Neoral AUCs in children and adults who underwent renal transplantation.

Cyclosporin A therapy in refractory non-infectious childhood uveitis

AIMS

To assess the immunosuppressive efficacy, steroid sparing effect and adverse effects of cyclosporin A (CsA) therapy in refractory non-infectious childhood uveitis.

METHODS

A retrospective case series review of the medical records of children on CsA therapy attending a tertiary referral centre for refractory endogenous uveitis was performed. Low dose (< or = 5.0 mg/kg/day) CsA therapy was started either as monotherapy or in combination with other agents. The CsA immunosuppressive efficacy was assessed by visual acuity and binocular indirect ophthalmoscopy (BIO) score outcomes and steroid sparing effect by growth charts and ability to withdraw or maintain a low steroid dose. Possible CsA adverse effects were monitored by routine biochemistry (including serum creatinine) and haematological tests, blood pressure recordings, and symptoms.

RESULTS

14 patients (25 eyes, 10 males, four females) were recruited with steroid failure as the most common CsA indication. Age (mean (SD)) at start of CsA therapy was 8.7 (4.1) years with a duration of CsA therapy of 20.9 (range 3.5-88.3) months at a maintenance CsA dose of 4.0 (1.0) mg/kg/day. From baseline, visual acuity improved or was maintained in 23 (92%) eyes and BIO score improved in 19 (76%) eyes. Height centiles were preserved and the maintenance prednisolone dose was 6.3 (3.3) mg/day, where required, in 10 (71%) patients. Nephrotoxicity was not observed, with transient systemic hypertension developing in one patient. Minor adverse effects were more common but were well tolerated.

CONCLUSIONS

Cyclosporin A therapy is effective and safe in the medium term, if closely monitored, in refractory non-infectious childhood uveitis.

Kidney function after 1:1 conversion to the cyclosporine microemulsion formulation in children with liver allografts

BACKGROUND

One-to-one (mg:mg) conversion from the conventional to the microemulsion formulation of cyclosporine (CsA) is advocated as a simple way to use the new therapeutic regimen. However, the potentially harmful effects of the conversion on kidney function in nonrenal transplant recipients are poorly known.

METHODS

Renal effects of the conversion were prospectively investigated in 22 pediatric liver transplant recipients (mean age, 8.4 years; mean time from transplantation, 3.2 years). Patients were followed for 12 months. Pharmacokinetic studies were performed at baseline and 5 days and 6 and 12 months after conversion.

RESULTS

Peak concentration, minimum concentration, average steady state concentration, and area under the concentration-versus-time curve increased by 60-130% after conversion. Graft losses, progressive deterioration of graft function, and acute rejection episodes did not occur. The mean glomerular filtration rate (GFR) was 103 ml/min/1.73 m2 at baseline and 100 ml/min/1.73 m2 after 12 months. However, 6 of the 22 patients showed at least a 15% (range, 16-38%) decrease in GFR between baseline and 6 months (P<0.01). They had a significantly higher increase in average steady state concentration between baseline and 6 months than the six patients with the best outcome in GFR during the same time period (164 ng/ml vs. 53 ng/ml, P<0.05). At this point (6 months), target CsA trough levels were reduced by 20-30%, while the mean area under the concentration-versus-time curve remained above that obtained at baseline. The GFR of three of the six patients subsequently improved.

CONCLUSIONS

One-to-one conversion can be performed safely in liver transplant recipients if strict follow-up is feasible.

Cyclosporin pharmacokinetics in paediatric transplant recipients

Cyclosporin is an essential component of the antirejection drug protocol used in the long term management of paediatric organ transplant recipients. This article looks at the pharmacokinetics of cyclosporin in paediatric kidney, heart, liver and bone marrow transplant recipients and critically evaluates its relationship to pharmacokinetic data in adult transplant recipients. There are limited data on the pharmacokinetics of cyclosporin in paediatric transplant recipients (14 publications provide the database) as compared with the adult transplant population. Study design, analytical methodology and age ranges of the individuals differ between studies, making comparative interpretation of pharmacokinetic data difficult. However, significant trends are noteworthy and these may influence dose administration guidelines and therapeutic monitoring standards for cyclosporin in the paediatric organ transplant recipient. The bioavailability of the oral formulations of cyclosporin is highly variable as with the adult population, but there appears to be a correlation between cyclosporin bioavailability and age with both the traditional oral formulation (Sandimmun) and the new microemulsion formulation (Neoral) in young liver transplant patients. Bowel length, presystemic metabolism in the gut wall, type of transplant and time since transplant are contributing factors in the variation of bioavailability patterns in paediatric transplant patients. The volume of distribution of cyclosporin does not appear to differ between paediatric and adult transplant recipients, but systemic clearance is comparatively higher in the paediatric population. In general, paediatric patients require higher doses of cyclosporin to achieve target blood concentrations of the drug which are equivalent to the values used in the adult population. Younger patients (less than 8 years of age) may be managed more effectively with a 3 times daily administration schedule rather than the twice daily schedule which is universally used for cyclosporin in the transplant population. The comparatively higher doses and more frequent administration schedule used in paediatric transplant recipients are the consequence of age-related differences in bioavailability and the possibility of increased metabolic clearance of the drug in younger patients.

Pharmacokinetics of a new microemulsion formulation of cyclosporin A (Neoral) in young patients after renal transplantation

Pharmacokinetics of the new galenic formulation of cyclosporin A, Neoral, (Sandoz) was examined in 12 stable young patients after renal transplantation. Six of these patients were tested before and 4 weeks after switching from the standard formulation Sandimmun to Neoral. No significant changes were observed in trough levels, Lmax, Cmax, and AUC0-12 h, but the absorption rate constant (Ka) increased (P = 0.03). Glomerular filtration rate, as assessed by inulin clearance, increased by more than 10% in three patients and decreased in two, and was usually associated with a respective drop and rise in Cmax and AUC0-12 h of cyclosporin A. The large interindividual variability in the response to the conversion to the new formulation points to a need for close monitoring of cyclosporin A trough levels and renal function after switching from Sandimmun to Neoral in this age group in order to avoid nephrotoxicity.

Progress in renal transplantation for children

Renal transplantation continues to be the goal of therapy for children with end-stage renal disease. Patient age, primary renal disease, psychosocial status, living versus cadaver donor allograft, optimal immunosuppressive therapy, urologic status, and maximization of growth and development must be considered in determining the optimal time for transplantation. Immunizations should be up to date, and the immune status of both the donor and the recipient with regard to Epstein-Barr virus, cytomegalovirus, human immunodeficiency virus, and hepatitis A, B, and C must be known. Prednisone, imuran, cyclosporine, and T cell antibodies remain the mainstay of immunosuppression. However, new therapies, such as FK-506, rapamycin, mofetil, brequinar, leflunomide, and human leukocyte antigen-derived peptides, are under investigation for use in transplantation. Complications, including infection, rejection, and malignancy, continue to be problematic in pediatric renal transplantation. Although patient and graft survival has improved over time, outcomes in pediatric renal transplantation continue to lag behind those in young adults.