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Background: Tacrolimus is a narrow therapeutic index medication, which requires therapeutic drug monitoring to optimize dosing based on systemic exposure. MITRA microsampling offers a convenient, minimally invasive approach for the collection of capillary blood samples from a finger prick versus conventional venous blood sampling for quantitation of tacrolimus blood concentrations. However, the suitability of MITRA microsampling for the determination of tacrolimus concentrations requires assessment in clinical settings., Methods: Paired venous (2 mL) and capillary (10 μL) blood samples were collected pre-tacrolimus dose and 1 and 3 hours postdose during routine outpatient visits from stable adult liver or kidney transplant patients receiving prolonged-release tacrolimus. Tacrolimus concentrations were determined by liquid chromatography-tandem mass spectrometry, and the concentrations obtained by the 2 sampling methods were compared by linear regression and Bland-Altman agreement analyses., Results: Samples were available for 82 transplant recipients (kidney, n = 41; liver, n = 41). A high correlation was observed between tacrolimus concentrations in capillary and venous blood samples (Pearson correlation coefficient, 0.97; Lin concordance coefficient, 0.87; slope of the fitted line, >1.0). Tacrolimus concentrations in capillary samples were 22.5% higher on average than in the corresponding venous blood samples (95% limits of agreement, 0.5%-44.6%). Similar results were observed in both transplant subgroups., Conclusions: MITRA finger prick sampling provides a convenient alternative to venipuncture for therapeutic drug monitoring in transplant recipients maintained on prolonged-release tacrolimus. When using the finger prick MITRA method, the positive bias in tacrolimus concentrations observed with this technique, when compared with venipuncture, needs to be taken into consideration., (Copyright © 2021 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology.)

The objectives of this study were to assess long-term graft survival, patient survival, renal function, and acute rejections in de novo kidney transplant recipients, treated with once-daily prolonged-release tacrolimus-based therapy. The study was a 5-year non-interventional prospective follow-up of patients from the ADHERE study, a Phase IV 12-month open-label assessment of patients randomized to receive prolonged-release tacrolimus in combination with mycophenolate mofetil (MMF) (Arm 1) or sirolimus (Arm 2). From 838 patients in the randomized study, 587 were included in the long-term follow-up, of whom 510 completed the study at year 5. At 1 year post-transplant, graft and patient survival rates were 93.0% and 97.8%, respectively, and at 5 years were 84.0% and 90.8%, respectively. Cox proportional hazards analysis showed no association between graft loss, initial randomized treatment arm, donor age, donor type, or sex. The 5-year acute rejection-free survival rate was 77.4%, and biopsy-confirmed acute rejection-free survival rate was 86.0%. Renal function remained stable over the follow-up period: mean ± SD eGFR 4-variable modification diet in renal disease formula (MDRD4) was 52.3 ± 21.6 ml/min/1.73 m 2 at 6 months and 52.5 ± 23.0 ml/min/1.73 m 2 at 5 years post-transplant. These findings support the role of long-term once-daily prolonged-release tacrolimus-based immunosuppression, in combination with sirolimus or MMF, for renal transplant recipients in routine clinical practice., (© 2019 The Authors. Transplant International published by John Wiley & Sons Ltd on behalf of Steunstichting ESOT.)

Tacrolimus has significantly improved outcomes for kidney transplant patients and remains the cornerstone of immunosuppressive therapy. While improvements in short-term outcomes in transplantation have been achieved in recent years, maintaining long-term graft survival remains a challenge in kidney transplantation. Minimizing risk factors for poor long-term kidney graft function and survival, and modifying tacrolimus regimens in the early and maintenance phases post-transplantation are essential to maintain long-term kidney transplant outcomes. Tacrolimus has a narrow therapeutic window, resulting in a tightly defined range of optimal drug exposure. Underimmunosuppression is associated with long-term risks, such as the development of donor-specific antibodies and antibody-mediated rejection, with a high possibility of a decline in kidney function and progression to graft failure. Conversely, prolonged overimmunosuppression carries a risk of drug-related adverse events. This review provides an overview of the differences in the formulation, delivery, and pharmacokinetic profiles between immediate- and prolonged-release tacrolimus and evaluates the effect of prolonged-release tacrolimus on the risk factors for poor outcomes in kidney transplantation. Recent evidence is used to provide guidance on target tacrolimus trough levels in the early and maintenance phases post-transplantation, with a view to improving long-term kidney graft function., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

There are limited clinical data regarding prolonged-release tacrolimus (PR-T) use in pediatric transplant recipients. This Phase 2 study assessed the efficacy and safety of PR-T in stable pediatric kidney, liver, and heart transplant recipients (aged ≥5 to ≤16 years) over 1 year following conversion from immediate-release tacrolimus (IR-T), on a 1:1 mg total-daily-dose basis. Endpoints included the incidence of acute rejection (AR), a composite endpoint of efficacy failure (death, graft loss, biopsy-confirmed AR, and unknown outcome), and safety. Tacrolimus dose and whole-blood trough levels (target 3.5-15 ng/ml) were also evaluated. Overall, 79 patients (kidney, n = 48; liver, n = 29; heart, n = 2) were assessed. Following conversion, tacrolimus dose and trough levels remained stable; however, 7.6-17.7% of patients across follow-up visits had trough levels below the target range. Two (2.5%) patients had AR, and 3 (3.8%) had efficacy failure. No graft loss or deaths were reported. No new safety signals were identified. Drug-related treatment-emergent adverse events occurred in 28 patients (35.4%); most were mild, and all resolved. This study suggests that IR-T to PR-T conversion is effective and well tolerated over 1 year in pediatric transplant recipients and highlights the importance of therapeutic drug monitoring to maintain target tacrolimus trough levels., (© 2019 Astellas Pharma Europe. Transplant International published by John Wiley & Sons Ltd on behalf of Steunstichting ESOT.)

This study was a Phase II, open-label, multicenter, single-arm, cross-over study comparing the pharmacokinetics (PK) of tacrolimus in stable pediatric kidney, liver, or heart allograft recipients converted from immediate-release tacrolimus (IR-T) to prolonged-release tacrolimus (PR-T). In Days -30 to -1 of screening period, patients received their IR-T-based regimen; during Days 1-7, patients received study IR-T (same dose as screening). On Day 7, the first 24-hours PK profile was taken; patients were then converted to PR-T (1 mg:1 mg), with a second 24-hours PK profile taken on Day 14. The primary end-point was tacrolimus area under the blood concentration-time curve over 24 hours (AUC 24 ); secondary end-points were maximum concentration C max and concentration at 24 hours C 24 . The predefined similarity interval for confidence intervals (CIs) of least squares mean (LSM) ratios was 80%-125%. The PK analysis set comprised 74 pediatric transplant recipients (kidney, n = 45; liver, n = 28; heart, n = 1). PR-T:IR-T LSM ratio (90% CI) was similar overall for AUC 24 , max , and C 24 , and for kidney and liver recipients for AUC 24 (LSM ratio, kidney 91.8%; liver 104.1%) and C 24 (kidney 90.5%; liver 89.9%). Linear relationship was similar between AUC 24 and C 24 , and between PR-T and IR-T (rho 0.89 and 0.84, respectively), suggesting that stable pediatric transplant recipients can be converted from IR-T to PR-T at the same total daily dose, using the same therapeutic drug monitoring method., (© 2019 The Authors. Pediatric Transplantation published by Wiley Periodicals, Inc.)

Tacrolimus granules were developed for patients who are unable to swallow capsules. Therapeutic drug monitoring (TDM) is required to optimize efficacy and safety, which is based on C trough for tacrolimus capsules. Pharmacokinetic (PK) data for tacrolimus granules are required to establish the basis for TDM in those who are unable to swallow capsules. In this phase IV study (NCT01371331) of children undergoing liver, kidney, or heart transplantation, patients received tacrolimus granules 0.15 mg/kg twice daily; first dose was administered within 24 hours of reperfusion. PK analysis samples were collected after reperfusion, after first dose of tacrolimus (Day 1), and at steady state (Day 7; >4 days stable dose). Of the 52 transplant recipients enrolled, 38 had two evaluable PK profiles. Mean AUC tau after first dose of tacrolimus was 211, 97, and 224 hour*ng/mL in liver, kidney, and heart transplant recipients, respectively; corresponding mean AUC tau at steady state was 195, 208, and 165 hour*ng/mL. C trough and AUC tau were positively correlated after first dose of tacrolimus and at steady state (Pearson's coefficients: r = 0.81 and r = 0.87, respectively). This study demonstrated that C trough is a reliable marker for TDM in pediatric transplant recipients treated with tacrolimus granules, consistent with TDM for other tacrolimus formulations., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Phase 2, parallel-group, multicenter, open-label, 4-week study, comparing PK of PR-T vs IR-T in de novo pediatric patients undergoing primary kidney, liver, or heart transplantation. Patients randomized 1:1 to receive once daily, PR-T-, or twice-daily, IR-T-based regimens; dose adjustments permitted after Day 1. Twenty-four-hour PK profiles collected on Days 1, 7, and 28. Primary endpoint: tacrolimus AUC 24 . Secondary end points included tacrolimus C 24 and C max . Endpoints compared between PR-T and IR-T on Days 1, 7, and 28. Predefined similarity interval for CIs of LSM ratios: 80%-125%. PK analysis set comprised 33 patients (PR-T, n = 15; IR-T, n = 18). Overall, AUC 24 and C max were lower on Day 1 vs 7 and 28. Geometric LSM ratios of PR-T:IR-T on Days 1, 7, and 28 were 66.3%, 92.5%, 99.9%, respectively, for AUC 24 ; 66.3%, 82.2%, 90.9% for C 24 ; and 77.3%, 120.3%, 92.2% for C max . AUC 24 90% CI within predefined similarity interval on Day 28; other 90% CIs fell outside. Linear relationship was similar between AUC 24 and C 24 , and between tacrolimus formulations, suggesting that the same therapeutic drug monitoring method can be used with both formulations in de novo pediatric allograft recipients., (© 2018 The Authors. Pediatric Transplantation published by Wiley Periodicals, Inc.)

Background: ADVANCE (NCT01304836) was a phase 4, multicenter, prospectively randomized, open-label, 24-week study comparing the incidence of posttransplantation diabetes mellitus (PTDM) with 2 prolonged-release tacrolimus corticosteroid minimization regimens., Methods: All patients received prolonged-release tacrolimus, basiliximab, mycophenolate mofetil and 1 bolus of intraoperative corticosteroids (0-1000 mg) as per center policy. Patients in arm 1 received tapered corticosteroids, stopped after day 10, whereas patients in arm 2 received no steroids after the intraoperative bolus. The primary efficacy variable was the diagnosis of PTDM as per American Diabetes Association criteria (2010) at any point up to 24 weeks postkidney transplantation. Secondary efficacy variables included incidence of composite efficacy failure (graft loss, biopsy-proven acute rejection or severe graft dysfunction: estimated glomerular filtration rate (Modification of Diet in Renal Disease-4) <30 mL/min per 1.73 m), acute rejection and graft and patient survival., Results: The full-analysis set included 1081 patients (arm 1: n = 528, arm 2: n = 553). Baseline characteristics and mean tacrolimus trough levels were comparable between arms. Week 24 Kaplan-Meier estimates of PTDM were similar for arm 1 versus arm 2 (17.4% vs 16.6%; P = 0.579). Incidence of composite efficacy failure, graft and patient survival, and mean estimated glomerular filtration rate were also comparable between arms. Biopsy-proven acute rejection and acute rejection were significantly higher in arm 2 versus arm 1 (13.6% vs 8.7%, P = 0.006 and 25.9% vs 18.2%, P = 0.001, respectively). Tolerability profiles were comparable between arms., Conclusions: A prolonged-release tacrolimus, basiliximab, and mycophenolate mofetil immunosuppressive regimen is efficacious, with a low incidence of PTDM and a manageable tolerability profile over 24 weeks of treatment. A lower incidence of biopsy-proven acute rejection was seen in patients receiving corticosteroids tapered over 10 days plus an intraoperative corticosteroid bolus versus those receiving an intraoperative bolus only.

Introduction: Tacrolimus has originally been registered as a twice-daily formulation (Prograf, Tac BID), although a once-daily formulation (Advagraf, Tac QD) is also available. A reduced intrapatient variability of Tac Cmin, a surrogate marker for 24-hour drug exposure (AUC0-24), has been suggested. The variability of AUC0-24 has never been studied prospectively yet. The purpose of this study was to investigate the change in intrapatient variability of Tac AUC0-24 after converting from Tac BID to Tac QD., Methods: Forty renal transplant patients on Tac BID were converted on a 1:1 (mg/mg) basis to Tac QD in an investigator-driven comparative pharmacokinetic (PK) study. AUC0-24 was determined five times before and after conversion. Duplicate samples were collected by the patients themselves using the dried blood spot method. The main outcome measure is the change in intrapatient variability of AUC0-24 expressed as coefficient of variation (CV). Moreover, the influence of Cyp3A5 genotype polymorphism on the change in CV was studied., Results: In total, 400 AUC0-24 profiles were available for analysis. Conversion to Tac QD resulted in a significant improvement in intra-patient CV from 14.1% to 10.9% (P=0.012). Patients with the Cyp3A5*1/*3 genotype (n=11) had a numerically larger improvement in CV than patients with the CYP3A5*3/*3 genotype., Conclusion: Intrapatient CV of Tac AUC0-24 improved after converting from Tac BID to Tac QD in stable renal transplant patients, especially in patients with the CYP3A5*1/3 genotype. Given the very strict protocol of this PK study, this improvement is most likely due to the different intrinsic PK properties of Tac QD and Tac BID.

Background: Tacrolimus is a well-established immunosuppressive agent for the treatment and prevention of solid organ graft rejection. It is available as an immediate-release, twice-daily formulation (Tacrolimus BID) and a prolonged-release, once-daily formulation (Tacrolimus QD). In a previous study of the pharmacokinetics (PK) of these formulations, mean systemic exposure [area under the curve from 0 to 24 hours (AUC0-24)] of tacrolimus on day 1 was approximately 30% lower for Tacrolimus QD than for Tacrolimus BID; by day 14, systemic exposure was similar; however, the mean dose of Tacrolimus QD was higher to achieve similar systemic exposure as Tacrolimus BID., Methods: To further compare the PK of the tacrolimus formulations during the first 2 weeks posttransplant, a substudy was performed in a subset of patients enrolled into a phase III trial in de novo kidney transplant recipients comparing Tacrolimus QD and Tacrolimus BID. To minimize the difference in exposure observed in the earlier study, tacrolimus therapy was initiated before transplant. The PK analysis set comprised 34 patients (17 patients per treatment group) who had 4 complete PK profiles and no major PK-related protocol violations., Results: Mean AUC0-24 of tacrolimus on day 1 was approximately 16% lower for Tacrolimus QD than for Tacrolimus BID, although by day 3 onward, the exposure was similar between treatment groups. Analysis of dose-normalized AUC0-24 (dose normalized to 0.1 mg/kg) showed a similar pattern. There was a good correlation between AUC0-24 and concentration of tacrolimus at 24 hours postdose for both formulations (Tacrolimus QD, r = 0.87; Tacrolimus BID, r = 0.92), and the slope of the line of best fit was similar., Conclusions: These results suggest that initiating tacrolimus therapy before transplant reduces the difference in exposure between Tacrolimus QD and Tacrolimus BID.

Background: A prolonged-release formulation of tacrolimus for once-daily administration (Tacrolimus QD) has been developed to offer potential improvements in patient adherence. This study compared the pharmacokinetics (PK) of tacrolimus in stable kidney transplant recipients before and after conversion from twice-daily tacrolimus (Tacrolimus BID) to Tacrolimus QD., Methods: This was an open-label, multicenter replicate design study in stable adult kidney transplant recipients (≥6 months posttransplantation) maintained on Tacrolimus BID. Patients underwent four sequential 14-day treatment periods of alternating Tacrolimus BID and QD (mg:mg conversion). Four 24-hour PK profiles were collected, one on the last day of each treatment period. Adverse events were also reported., Results: A total of 60 of 69 patients completed all 4 PK profiles. Steady-state tacrolimus area under the curve from 0 to 24 hours and Cmin were comparable for both formulations, with treatment ratio means (90% confidence intervals) of 92.9% (89.8%-96.0%) and 90.9% (87.3%-94.6%), respectively (acceptance interval: 80%-125%). Both formulations were well tolerated, with renal function remaining stable over the 8-week period. There was a good correlation between area under the curve from 0 to 24 hours and Cmin for Tacrolimus QD and BID (r = 0.88 and 0.82, respectively). The relationship between these two parameters was also similar., Conclusions: The results of this study provide evidence for safe conversion from Tacrolimus BID to QD with appropriate trough concentration monitoring.

Background: The once-daily formulation of tacrolimus has been reported to exhibit the same efficacy and safety profile as compared with the immediate-release form administered twice daily. However, as a result of differences in their pharmacokinetic (PK) profile, the PK models or Bayesian estimators (MAP-BE) previously developed for the immediate-release formulation cannot be used for the new once-daily formulation. Using the PK information obtained from a Phase II trial, the aim of this study was to explore the feasibility of developing a PK model and a MAP-BE able to estimate, on the basis of a routinely applicable limited sampling strategy, tacrolimus individual PK parameters and AUC0-24h in de novo renal transplant patients given the once-daily formulation., Methods: Twelve de novo kidney transplant recipients receiving once-daily tacrolimus as part of their immunosuppressive regimen provided full PK profiles (17 concentration time points over 24 hours) on Days 14 and 42 posttransplantation. On the basis of a one-compartment open model with absorption described as following a double gamma distribution, a classic iterative two-stage method was applied to develop MAP-BEs. All the limited sampling strategies with a maximum of three sampling times within 4 hours postdose were tested for Bayesian forecasting with the aim of accurately estimating the AUC0-24h., Results: Once-daily tacrolimus exhibited a high interpatient PK variability with coefficients of variation of 34.3% and 36.2% for AUC0-24h/dose (mg/kg) on Days 14 and 42, respectively. Regression analysis between C0 and AUC0-24h yielded r = 0.68 and 0.76 at these two periods, respectively. The iterative two-stage approach led to the development of a different MAP-BE for each posttransplantation period, which allowed estimation of once-daily tacrolimus pharmacokinetics and AUC0-24h on the basis of a C0-C1h-C3h sampling schedule. The mean bias of the Bayesian versus reference (trapezoidal) AUCs was 4.2% +/- 6.1% (range, -11.8% to +11.2%; root mean square error = 7.1%) on Day 14 and 0.2% +/- 7.9% (range, -12.9% to +14.1%; root mean square error = 7.8%) on Day 42., Conclusion: A PK model and Bayesian estimators allowing estimation of tacrolimus AUC0-24h based on a routinely applicable limited sampling strategy were developed for once-daily tacrolimus in renal transplantation. Further validation in independent groups of patients is required to confirm their applicability for optimizing the monitoring of once-daily tacrolimus in routine clinical practice or to conduct observational or comparative therapeutic drug monitoring clinical trials.

Although there are experimental reports of cytochrome P450 3A4 iso-enzyme (CYP3A4) induction by glucocorticoids, there are no clinical reports about an interaction between tacrolimus and steroids. Therefore, tacrolimus trough level and dose were compared after dose-normalization before and after withdrawal of prednisolone. After withdrawal of 5 mg prednisolone, the median tacrolimus dose-normalized level increased by 14% in the retrospective ( n=54), and by 11% in the prospective ( n=8) part of the study. After withdrawal of 10 mg, this increase was 33% ( n=30) and 36% ( n=14), respectively. An additional pharmacokinetic part of the study ( n=8) revealed an 18% increase in AUC ( P=0.05) after withdrawal of 5 mg prednisolone, which is compatible with a reduced metabolism after steroid withdrawal. The significant increase in tacrolimus exposure after steroid withdrawal may on the one hand counteract the reduction in immunosuppression intended by steroid withdrawal, and, on the other hand, may result in an increase of serum creatinine which could be misinterpreted as rejection.

This paper reviews the pharmacokinetics of tacrolimus, with special reference to its combination with adjunctive immunosuppressants. Oral bioavailability of tacrolimus, which is variable between patients, averages approximately 25%. This is largely due to extrahepatic metabolism of tacrolimus in the gastrointestinal epithelium. Nevertheless, intra-patient variability is low, as evidenced by the small number of dose changes required to maintain patients within the recommended tacrolimus target levels. Tacrolimus is distributed extensively in the body with most partitioned outside the blood compartment. Concentrations of tacrolimus in blood are used as a surrogate marker of clinically relevant concentration of the drug at the site(s) of action. Convenient whole-blood sampling within a +/-2-h window around 12 h post-dose (C(min)) is highly predictive of systemic exposure to tacrolimus and is thus used to optimise therapy. Sampling at other time-points offers no advantage over C(min) monitoring. The interactions of tacrolimus with other immunosuppressive agents are well characterized. After cessation of concomitant corticosteroid treatment, exposure to tacrolimus increases by approximately 25%. In contrast, there is no pharmacokinetic interaction between mycophenolate mofetil (MMF) and tacrolimus. Therefore, systemic exposure to the active metabolite of MMF, mycophenolic acid, is higher with MMF-tacrolimus combination than with MMF-cyclosporin combination. Therefore, 1 g/day MMF may be an adequate maintenance dose in tacrolimus-based regimens. Co-administration of tacrolimus and sirolimus, while having no effect on exposure to sirolimus, results in reduced exposure to tacrolimus at sirolimus doses of 2 mg/day and above. In conclusion, tacrolimus levels should be monitored when sirolimus is co-administered at doses >2 mg/day and after cessation of corticosteroid treatment.

Background: An association between hepatitis C virus and (post-transplant) diabetes mellitus has been reported., Methods: We report a patient on tacrolimus-based immunosuppression who developed an episode of post-transplant diabetes mellitus (PTDM) 2 years after renal transplantation, after contracting a hepatitis C infection. Her glucose metabolism was evaluated regularly by intravenous glucose tolerance tests before and after the PTDM episode., Results: Before contracting hepatitis C, the patient's insulin resistance and insulin secretion were normal. After contracting hepatitis C, tacrolimus exposure increased, insulin resistance increased, and insulin secretion decreased markedly. Despite low tacrolimus exposure in the last 4 years, glucose metabolism did not recover completely. Although PTDM resolved and insulin resistance normalized, pancreatic beta cell secretion remained impaired by approximately 50% compared with the period before hepatitis C infection., Conclusion: After an initial increase in insulin resistance, insulin secretion decreased markedly in a patient who contracted hepatitis C 12 to 22 months after renal transplantation. This change resulted in an episode of PTDM. Increased tacrolimus exposure secondary to reduced cytochrome P-450 metabolism as a result of impaired hepatocellular function at the time of the development of PTDM seems a likely explanation for the marked decrease in insulin secretion. Viral toxicity to the beta cell might be an additional explanation. The latter might be suspected from several reports about an association between diabetes mellitus and hepatitis C in patients who do not use drugs that interfere with glucose metabolism., (Copyright 2002 by the National Kidney Foundation, Inc.)

Background and Objective: Given that a high intrapatient variability (IPV) of tacrolimus whole blood concentration increases the risk for a poor kidney transplant outcome, some experts advocate routine IPV monitoring for detection of high-risk patients. However, attempts to estimate the variance of tacrolimus trough concentrations (TTC) are limited by the need for patients to receive a fixed dose over time and/or the use of linear statistical models. A goal of this study is to overcome the current limitations through the novel application of statistical methodology generalizing the relationship between TTC and dose through the use of nonparametric functional regression modeling. Methods: With TTC as a response and dose as a covariate, the model employs an unknown bivariate function, allowing for the potentially complex, nonlinear relationship between the two parameters. A dose-adjusted variance of TTC is then derived based on standard functional principal component analysis (FPCA). To assess the model, it was compared against an FPCA-based model and linear mixed-effects models using prediction error, bias, and coverage probabilities for simulated data as well as phase III data from the Astellas new drug application studies for extended-release tacrolimus. Results: Our numerical investigation indicates that the new model better predicts dose-adjusted TTCs compared with the prediction of linear mixed effects models. Estimated coverage probabilities also indicate that the new model accurately accounts for the variance of TTC during the periods of large fluctuation in dose, whereas the linear mixed effects model consistently underestimates the coverage probabilities because of the inaccurate characterization of TTC fluctuation. Conclusion: This is the first known application of a functional regression model to assess complex relationships between TTC and dose in a real clinical setting. This new method has applicability in future clinical trials including real-world data sets due to flexibility of the nonparametric modeling approach. [ABSTRACT FROM AUTHOR]

Tacrolimus granules were developed for patients who are unable to swallow capsules. Therapeutic drug monitoring (TDM) is required to optimize efficacy and safety, which is based on Ctrough for tacrolimus capsules. Pharmacokinetic (PK) data for tacrolimus granules are required to establish the basis for TDM in those who are unable to swallow capsules. In this phase IV study (NCT01371331) of children undergoing liver, kidney, or heart transplantation, patients received tacrolimus granules 0.15 mg/kg twice daily; first dose was administered within 24 hours of reperfusion. PK analysis samples were collected after reperfusion, after first dose of tacrolimus (Day 1), and at steady state (Day 7; >4 days stable dose). Of the 52 transplant recipients enrolled, 38 had two evaluable PK profiles. Mean AUCtau after first dose of tacrolimus was 211, 97, and 224 hour*ng/mL in liver, kidney, and heart transplant recipients, respectively; corresponding mean AUCtau at steady state was 195, 208, and 165 hour*ng/mL. Ctrough and AUCtau were positively correlated after first dose of tacrolimus and at steady state (Pearson's coefficients: r = 0.81 and r = 0.87, respectively). This study demonstrated that Ctrough is a reliable marker for TDM in pediatric transplant recipients treated with tacrolimus granules, consistent with TDM for other tacrolimus formulations. [ABSTRACT FROM AUTHOR]

Background and aims: This multicenter trial compared immediate‐release tacrolimus (IR‐T) vs prolonged‐release tacrolimus (PR‐T) in de novo kidney, liver, and heart transplant recipients aged <16 years. Each formulation had similar pharmacokinetic (PK) profiles. Follow‐up efficacy and safety results are reported herein. Materials and methods: Patients, randomized 1:1, received once‐daily, PR‐T or twice‐daily, IR‐T within 4 days of surgery. After a 4‐week PK assessment, patients continued randomized treatment for 48 additional weeks. At Year 1, efficacy assessments included the number of clinical acute rejections, biopsy‐confirmed acute rejection (BCAR) episodes (including severity), patient and graft survival, and efficacy failure (composite of death, graft loss, BCAR, or unknown outcome). Adverse events were assessed throughout. Results: The study included 44 children. At Year 1, mean ± standard deviation tacrolimus trough levels were 6.6 ± 2.2 and 5.4 ± 1.6 ng/mL, and there were 2 and 7 acute rejection episodes in the PR‐T and IR‐T groups, respectively. No cases of graft loss or death were reported during the study. The overall efficacy failure rate was 18.2% (PR‐T n = 1; IR‐T n = 7). Conclusions: In pediatric de novo solid organ recipients, the low incidence of BCAR and low efficacy failure rate suggest that PR‐T‐based immunosuppression is effective and well tolerated to 1‐year post‐transplantation. [ABSTRACT FROM AUTHOR]