Cyclosporin A absorption profiles in children with nephrotic syndrome

Therapeutic drug monitoring in childhood idiopathic nephrotic syndrome: a state of the art review

Immunosuppressants are commonly used as steroid-sparing agents in childhood idiopathic nephrotic syndrome (NS) to induce and sustain remissions. These drugs have narrow therapeutic indices with high inter- and intra-patient variability. Therapeutic drug monitoring (TDM) would therefore be essential to guide the prescription. Multiple factors in NS contribute to additional variability in drug concentrations, especially during relapses. In this article, we review the currently available evidence of TDM in NS and suggest a practical approach for clinicians' reference.

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.

Effectiveness and nephrotoxicity of a 2-year medium dose of cyclosporine in pediatric patients with steroid-dependent nephrotic syndrome: determination of the need for follow-up kidney biopsy

BACKGROUND

High dose of cyclosporine (CyA) for ≥2 years in children with steroid-dependent nephrotic syndrome (SDNS) increases the risk for nephropathy. Considering this, risk can be lowered with lower doses of CyA; we evaluated the effects of a medium dose of CyA, with target serum level, C2, of 450 ng/ml, over a 2-year period of observation, to determine the need for follow-up kidney biopsy.

METHODS

We retrospectively evaluated C2 levels in 38 patients (17 males, 5.2 ± 2.9 years old) with SDNS at treatment initiation, at 6, 12 and 18 months during treatment, and at the time of kidney biopsy, 2-year after treatment initiation. Fifteen patients were also treated with mizoribine or mycophenolate mofetil. A number of relapses-per-patient-per-year, relative to SDNS onset and initiation of CyA treatment, were evaluated. Serum levels of total protein, albumin and total cholesterol, blood urea nitrogen level, and the estimated glomerular filtration rate were measured at treatment initiation and at 1- and 2-year post-treatment initiation.

RESULTS

Only one very mild case of CyA-associated nephrotoxicity was identified based on biopsy results at 2-year post-treatment initiation. C2 concentrations were maintained at 422.2 ± 133.5 ng/ml and the number of relapses decreased from 3.0 relapses-per-patient-per-year prior to CyA treatment to 0.47 relapses-per-patient-per-year after CyA treatment. No effects of the treatment on the estimated glomerular filtration rate were noted.

CONCLUSION

A 2-year treatment with a medium dose of cyclosporine A with or without other immunosuppressive agents is relatively safe with regard to the development of cyclosporine A nephrotoxicity.

Second-line options for refractory steroid-sensitive and -resistant nephrotic syndrome

Although initially, many children with idiopathic nephrotic syndrome respond to steroid therapy, a repeated course for patients with relapses often causes significant steroid toxicity. Patients with frequent relapses or steroid dependency thus require alternative treatment, and so far, cyclophosphamide or levamisole have been regarded as first-choice options, although the latter is no longer available in many countries. Data are accumulating that mycophenolic acid may be an alternative for these patients. Calcineurin inhibitors (cyclosporine A or tacrolimus) are usually effective and are often used after cytotoxic treatment, but long-term treatment is necessary, raising concerns regarding the accumulation of side effects. Still, some patients show a tendency to relapse even on this maintenance regimen and some even have a refractory course that creates a medical dilemma. For this situation, recent data have demonstrated an effect of monoclonal antibodies directed to B cells - rituximab, a drug that may also prove to be a therapeutic option in less complicated cases. Patients that do not respond to initial steroid treatment need genetic testing and a renal biopsy, since focal segmental glomerulosclerosis may be present. Treatment options include pulse methylprednisolone, often in addition to calcineurin inhibitors (mainly cyclosporine but also, recently, tacrolimus). Cyctotoxic treatment, especially intravenous cyclophosphamide, has been found to be effective in steroid-resistant nephrotic syndrome by some studies but is inferior to calcineurin inhibitors. In addition, mycophenolic acid and rituximab have been used in children with primary focal segmental glomerulosclerosis; however, response seems to be inferior in comparison with patients with steroid-sensitive nephrotic syndrome. Taken together, idiopathic nephrotic syndrome, including steroid-sensitive as well as steroid-resistant patients, is a potentially serious disorder. Although much progress has been made in recent years and a wide arsenal of immunological interventions is available, some patients have a treatment refractory course. Prospective studies or at least standardization of treatment for complicated cases is urgently needed.

Pharmacokinetics of cyclosporin--a microemulsion in children with idiopathic nephrotic syndrome

OBJECTIVE

We present a prospective study of a microemulsion of cyclosporin to treat idiopathic nephrotic syndrome in ten children with normal renal function who presented cyclosporin trough levels between 50 and 150 ng/ml and achieved complete remission with cyclosporin. To compare the pharmacokinetic parameters of cyclosporin in idiopathic nephrotic syndrome during remission and relapse of the nephrotic state.

METHOD

The pharmacokinetic profile of cyclosporin was evaluated with the 12-hour area under the time-concentration curve (auc0-12) using seven time-point samples. This procedure was performed on each patient during remission and relapse with the same cyclosporin dose in mg/kg/day. The 12-hour area under the time-concentration curve was calculated using the trapezoidal rule. All of the pharmacokinetic parameters and the resumed 4-hour area under the time-concentration curve were correlated with the 12-hour area under the time-concentration curve. ClinicalTrials.gov: NCT01616446.

RESULTS

There were no significant differences in any parameters of the pharmacokinetic of cyclosporin during remission and relapse, even when the data were normalized by dose. The best correlation with the 12-hour area under the time-concentration curve was the 4-hour area under the time-concentration curve on remission and relapse of the disease, followed by the 2-hour level after cyclosporin (c2) dosing in both disease states.

CONCLUSIONS

These data indicate that the same parameters used for cyclosporin therapeutic monitoring estimated during the nephrotic state can also be used during remission. Larger controlled studies are needed to confirm these findings.

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.

New therapies in steroid-sensitive and steroid-resistant idiopathic nephrotic syndrome

Although many children with idiopathic nephrotic syndrome (INS) respond initially to steroid therapy, repeated courses for patients with relapses often cause significant steroid toxicity. Patients with frequent relapses who develop steroid dependency thus require alternative treatment. The first such options have been considered to be cyclophosphamide or levamisole, although the latter is no longer available in many countries. There is also an increasing body of data indicating that mycophenolic acid (MPA) may be an alternative for these patients. Calcineurin inhibitors (cyclosporine A or tacrolimus) are usually effective and often used after cytotoxic treatment, but long-term treatment with these agents is necessary, raising concerns of a possible accumulation of side effects. Some patients show a tendency to relapse even on such maintenance regimens, and some even have a refractory course that creates a medical dilemma. For this situation, recent data indicate that monoclonal antibodies directed to B-cells (e.g. rituximab) may have some effect and that such drugs may also prove to be a therapeutic option in less complicated cases. Patients that do not respond to steroid treatment need genetic testing and a renal biopsy since focal segmental glomerulosclerosis (FSGS) may be present. Treatment options include pulse methylprednisolone, often in addition to calcineurin inhibitors, mainly in the form of cyclosporine, but tacrolimus has also come into recent favor. Some studies have found cytotoxic treatment, especially intravenous cyclophosphamide, to be effective in steroid resistant nephrotic syndrome, but it seems to be inferior to calcineurin inhibitors. MPA and rituximab have also been used in children with primary FSGS, but the response seems to be inferior to that in patients with steroid sensitive nephrotic syndrome. Taken together, INS in both steroid-sensitive and steroid-resistant patients is a potentially complicated disorder, and despite a wide arsenal of immunological interventions, some patients have a treatment refractory course. Prospective studies or at least standardized treatment for complicated cases is urgently needed.

Long-term outcome of idiopathic steroid-resistant nephrotic syndrome: a multicenter study

Long-term outcome of idiopathic steroid-resistant nephrotic syndrome was retrospectively studied in 78 children in eight centers for the past 20 years. Median age at onset was 4.4 years (1.1-15.0 years) and the gender ratio was 1.4. Median follow-up period was 7.7 years (1.0-19.7 years). The disease in 45 patients (58%) was initially not steroid-responsive and in 33 (42%) it was later non-responsive. The main therapeutic strategies included administration of ciclosporine (CsA) alone (n = 29; 37%) and CsA + mycophenolate mofetil (n = 18; 23%). Actuarial patient survival rate after 15 years was 97%. Renal survival rate after 5 years, 10 years and 15 years was 75%, 58% and 53%, respectively. An age at onset of nephrotic syndrome (NS) > 10 years was the only independent predictor of end-stage renal disease (ESRD) in a multivariate analysis using a Cox regression model (P < 0.001). Twenty patients (26%) received transplants; ten showed recurrence of the NS: seven within 2 days, one within 2 weeks, and two within 3-5 months. Seven patients lost their grafts, four from recurrence. Owing to better management, kidney survival in idiopathic steroid-resistant nephrotic syndrome (SRNS) has improved during the past 20 years. Further prospective controlled trials will delineate the potential benefit of new immunosuppressive treatment.

Population pharmacokinetic study of cyclosporine in patients with nephrotic syndrome

Cyclosporine (CsA) is widely used in the treatment of nephrotic syndrome (NS). A population pharmacokinetic (PopPK) model was developed using trough blood CsA concentration data from 106 patients with NS. The pharmacokinetic analysis was performed using NONMEM with 1-compartment linear model and first-order elimination. Proportional and additive error models were used to describe the interindividual and intraindividual variabilities, respectively. Body weight (WT), serum albumin level (ALB), and combination therapy with rifampicin were found to be the most significant covariates explaining the variability of the apparent clearance (CL/F) of CsA among patients. The final model was as follows: TVCL/F=34.1x(WT/67.6)(1.08)x(1+RFAx0.67)x(1-ALBx0.0088); TVV/F=3.5xWT; Ka=1.28 fixed; where RFA=1 with concurrent rifampicin use and 0 otherwise. The interindividual variabilities of CL/F and V/F were 18% and 27%, respectively. The residual error was 0.064 mg/L. The mean+/-SD of CL/F and V/F of the 106 patients were 23.5+/-7.2 L/h and 232.3+/-71.5 L, respectively. The reliability and stability of the PopPK model were confirmed by nonparametric bootstrap procedure.

Correlation between finger-prick and venous ciclosporin levels: association with gingival overgrowth and hypertrichosis

The aims of this study were (1) to ascertain ciclosporin C(2) levels currently being achieved in children with steroid-sensitive nephrotic syndrome (SSNS) and renal transplants (RTs), (2) to determine the feasibility of the use of finger-prick samples for the measurement of ciclosporin levels, and (3) to identify any correlation between hypertrichosis or gingival overgrowth (GO) and level of ciclosporin 2 h post-dose (C(2)). Seventy-two children (39 with SSNS, 33 with RT) participated. Ciclosporin 12 h trough (C(12)) and C(2) levels were measured in venous and finger-prick samples by high-performance liquid chromatography tandem mass spectroscopy. Photographs of the teeth and back were taken for assessment of GO and hypertrichosis. Mean (+/-SD) C(2) levels in the SSNS and RT groups were 512 (+/-181) microg/l and 471 (+/-229) microg/l. There was a highly significant relationship between venous and finger-prick ciclosporin levels (r(2) = 0.96, P < 0.0001). Fourteen children had severe GO. There was a small, though statistically significant, impact of ciclosporin level on GO (C(2) r(2) = 0.12, P = 0.003 and C(12) r(2) = 0.06, P = 0.038) but no correlation with dose (milligrammes per kilogramme per day or milligrammes per square metre per day) or duration. Seventeen children had moderate or severe hypertrichosis, this being more common in children of South Asian ethnicity (P < 0.0001). There was no correlation between ciclosporin exposure or duration and hypertrichosis. Finger-prick blood sampling may serve as a practical alternative to venepuncture in children receiving ciclosporin.

Increased cyclosporine bioavailability induced by experimental nephrotic syndrome in rats

Components of whole blood and plasma are highly altered during the presentation of nephrotic syndrome. The present study was aimed to explore the influence of nephrotic syndrome on the pharmacokinetics of cyclosporine (CsA) (10 mg/kg) administered i.v. to control or puromycin-induced nephrotic rats (P-NS). We found an increase in CsA bioavailability in the nephrotic group compared with controls. The area under the curve of blood CsA versus time (AUCiv) increased from 27.7 ± 5.3 to 60.6 ± 13.8 μg·h·mL–1in control and P-NS rats, respectively. The AUCivaugmentation was positively correlated with cholesterol levels. On the other hand, the total body clearance was significantly lower (0.38 ± 0.06 vs. 0.17 ± 0.03 L·(kg body mass)–1·h–1) and the volume of distribution at steady state (3.70 ± 0.52 vs. 2.85 ± 0.32 L/kg) was significantly smaller in nephrotic rats as compared with control. These pharmacokinetic changes lead to a longer terminal half-life of CsA in P-NS rats (11.8 ± 1.6 vs. 6.9 ± 0.91 h). We conclude that the physiopathologic changes induced by the nephrotic syndrome in P-NS animals result in a significant increase in CsA blood exposure by both the decrease in drug distribution and the reduction in elimination rate of CsA.

Decreased cyclosporine exposure during the remission of nephrotic syndrome

In this paper, we report the pharmacokinetics changes observed in seven children with steroid-resistant nephrotic syndrome (SRNS). They received cyclosporine A (CsA) microemulsion 6 mg/kg/day and, one week later, they were admitted to perform a 12-h pharmacokinetic profile with eight time sample points. The pharmacokinetic profile was repeated at 24 weeks of treatment, when all patients achieved remission. Blood concentration against time curves were constructed for each patient at weeks 1 and 24 of CsA treatment. Peak concentrations (C (max)) and the time needed to reach peak concentrations (t (max)) were directly determined from these plots. The area under the curve (AUC) was estimated by the trapezoidal rule. There was a statistically significant difference of the AUC, trough levels, and t (max) between weeks 1 and 24, with a decrease of AUC from 5,211 ng*h/ml in week 1 to 3,289 ng*h/ml in week 24, the trough levels decreased from 157 ng/ml to 96 ng/ml, and the t (max) decreased from 1.85 h to 1.00 h. The higher CsA bioavailability during the nephrotic state has to be considered when managing patients, since the target AUC cannot be the same throughout the treatment.

Prediction of systemic exposure to cyclosporine in Japanese pediatric patients

The monitoring of the blood concentration at 2 h (C(2)) after the oral administration of a cyclosporine (CsA) microemulsion was reconfirmed to be useful for the prediction of systemic exposure, the area under the blood concentration-time curve from 0 to 4 h (AUC(0-4)), in a group of Japanese patients, consisting of 33 children aged 5-15 years and 19 young adults aged 16-27 years, with a greater correlation for C(2) (r = 0.927) than the trough concentration (r = 0.488). The dose-normalized AUC(0-4) was independent of gender or indications for CsA, while it depended on body size, i.e., the age (P = 0.065) and total body weight (P = 0.026). MDR1 C3435T had a weak, but insignificant effect (P = 0.072); it was about 22-31% lower in the patients with TT(3435). Co-administration of a steroid and further treatment with nifedipine had a more intensive effect (P = 0.018); co-administration resulted in a 51% increase in the dose-normalized AUC(0-4). A strong effect was also observed for the serum total cholesterol level (P = 0.001). Collectively, the discrepancies in the results on MDR1 C3435T among investigators might be due to variability in the age/total body weight, co-administration drugs or serum lipid level.

MDR1 genotype-related pharmacokinetics: fact or fiction?

Multidrug resistant transporter MDR1/P-glycoprotein, the gene product of MDR1, is a glycosylated membrane protein of 170 kDa, belonging to the ATP-binding cassette superfamily of membrane transporters. A number of various types of structurally unrelated drugs are substrates for MDR1, and MDR1 and other transporters are recognized as an important class of proteins for regulating pharmacokinetics. The first investigation of the effects of MDR1 genotypes on pharmacotherapy was reported in 2000; a silent single nucleotide polymorphism (SNP), C3435T in exon 26, was found to be associated with the duodenal expression of MDR1, and thereby the plasma concentration of digoxin after oral administration. In the last 5 years, clinical studies have been conducted around the world on the association of MDR1 genotype with MDR1 expression and function in tissues, and with the pharmacokinetics and pharmacodynamics of drugs; however, there are still discrepancies in the results on C3435T. In 1995, a novel concept to predict in vivo oral pharmacokinetic performance from data on in vivo permeability and in vitro solubility has been proposed, and this Biopharmaceutical Classification System strongly suggested that the effects of intestinal MDR1 on the intestinal absorption of substrates is minimal in the case of commercially available oral drugs, and therefore MDR1 genotypes are little associated with the pharmacokinetics after oral administration. This review summarizes the latest reports for the future individualization of pharmacotherapy based on MDR1 genotyping, and attempts to explain discrepancies.