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Aims: Dried blood volumetric absorptive microsamples (VAMS) may facilitate home-based sampling to enhance therapeutic drug monitoring after transplantation. This study aimed to clinically validate a liquid chromatography-tandem mass spectrometry assay using 2 VAMS devices with different sampling locations (Tasso-M20 for the upper arm and Mitra for the finger). Patient preferences were also evaluated., Methods: Clinical validation was performed for tacrolimus and mycophenolic acid by comparison of paired VAMS and venipuncture samples using Passing-Bablok regression and Bland-Altman analysis. Conversion of mycophenolic acid VAMS to serum concentrations was evaluated using haematocrit-dependent formulas and fixed correction factors defined a priori. Patients' perspectives, including useability, acceptability and feasibility, were also investigated using established questionnaires., Results: Paired samples (n = 50) were collected from 25 kidney transplant recipients. Differences for tacrolimus whole-blood concentration were within ±20% for 86 and 88% of samples from the upper arm and fingerstick, respectively. Using correction factors of 1.3 for the upper-arm and 1.47 for finger-prick samples, 84 and 76% of the paired samples, respectively, were within ±20% for mycophenolic acid serum concentration. Patient experience surveys demonstrated limited pain and acceptable useability of the upper-arm device., Conclusions: Tacrolimus and mycophenolic acid can be measured using 2 common VAMS devices with similar analytical performance. Patients are supportive of home-based monitoring with a preference for the Tasso-M20 device., (© 2024 The Author(s). British Journal of Clinical Pharmacology published by John Wiley & Sons Ltd on behalf of British Pharmacological Society.)

Medication nonadherence after solid organ transplantation is recognized as an important impediment to long-term graft survival. Yet, assessment of adherence is often not part of routine care. In this Personal Viewpoint, we call for the transplant community to consider implementing a systematic process to screen and assess medication adherence. We believe acceptable tools are available to support integrating adherence assessments into the electronic health record. Creating a standard assessment can be done efficiently and cost-effectively if we come together as a community. More importantly, such monitoring can improve outcomes and strengthen provider-patient relationships. We further discuss the practical challenges and potential rebuttals to our position., Competing Interests: Declaration of competing interest The authors of this manuscript have no conflicts of interest to disclose as described by the American Journal of Transplant-ation., (Copyright © 2024 American Society of Transplantation & American Society of Transplant Surgeons. All rights reserved.)

Tacrolimus is widely reported to display diurnal variation in pharmacokinetic parameters with twice-daily dosing. However, the contribution of chronopharmacokinetics versus food intake is unclear, with even less evidence in the pediatric population. The objectives of this study were to summarize the existing literature by meta-analysis and evaluate the impact of food composition on 24-hour pharmacokinetics in pediatric kidney transplant recipients. For the meta-analysis, 10 studies involving 253 individuals were included. The pooled effect sizes demonstrated significant differences in area under the concentration-time curve from time 0 to 12 hours (standardized mean difference [SMD], 0.27; 95% confidence interval [CI], 0.03-0.52) and maximum concentration (SMD, 0.75; 95% CI, 0.35-1.15) between morning and evening dose administration. However, there was significant between-study heterogeneity that was explained by food exposure. The effect size for minimum concentration was not significantly different overall (SMD, -0.09; 95% CI, -0.27 to 0.09) or across the food exposure subgroups. A 2-compartment model with a lag time, linear clearance, and first-order absorption best characterized the tacrolimus pharmacokinetics in pediatric participants. As expected, adding the time of administration and food composition covariates reduced the unexplained within-subject variability for the first-order absorption rate constant , but only caloric composition significantly reduced variability for lag time. The available data suggest food intake is the major driver of diurnal variation in tacrolimus exposure, but the associated changes are not reflected by trough concentrations alone., (© 2023 The Authors. The Journal of Clinical Pharmacology published by Wiley Periodicals LLC on behalf of American College of Clinical Pharmacology.)

Background: Volumetric absorptive microsamples (VAMS) can support pharmacokinetic / pharmacodynamic studies. We present the bioanalytical method development for the simultaneous quantification of ampicillin, cefepime, ceftriaxone, meropenem, piperacillin, tazobactam, and vancomycin from VAMS. Methods & results: Optimal extraction, chromatographic, and mass spectrometry conditions were identified. Maximum extraction recoveries included 100 μl of water for rehydration and methanol for protein precipitation. Chromatographic separation used Phenomenex Kinetex ™ Polar C18 column with a mobile phase comprising water/acetonitrile with formic acid and was fully validated. Hematocrit effects were only observed for vancomycin. Samples were stable for 90 days at -80°C except for meropenem, which was stable for 60 days. Conclusion: Multiple antibiotics can be assayed from a single VAMS sample to facilitate pharmacokinetic/pharmacodynamic studies.

Background: Volumetric absorptive microsampling (VAMS) is an emerging technique that may support multisample collection to enhance therapeutic drug monitoring in solid organ transplantation. This review aimed to assess whether tacrolimus and mycophenolic acid can be reliably assayed using VAMS and to identify knowledge gaps by providing granularity to existing analytical methods and clinical applications., Methods: A systematic literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The PubMed, Embase, and Scopus databases were accessed for records from January 2014 to April 2022 to identify scientific reports on the clinical validation of VAMS for monitoring tacrolimus and mycophenolic acid concentrations. Data on the study population, sample sources, analytical methods, and comparison results were compiled., Results: Data from 12 studies were collected, including 9 studies pertaining to tacrolimus and 3 studies on the concurrent analysis of tacrolimus and mycophenolic acid. An additional 14 studies that provided information relevant to the secondary objectives (analytical validation and clinical application) were also included. The results of the clinical validation studies generally met the method agreement requirements described by regulatory agencies, but in many cases, it was essential to apply correction factors., Conclusionss: Current evidence suggests that the existing analytical methods that use VAMS require additional optimization steps for the analysis of tacrolimus and mycophenolic acid. The recommendations put forth in this review can help guide future studies in achieving the goal of improving the care of transplant recipients by simplifying multisample collection for the dose optimization of these drugs., Competing Interests: None of the authors report conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Volumetric absorptive microsampling may reduce the blood collection burden associated with therapeutic drug monitoring of immunosuppression to prevent organ transplant rejection. This work describes the development of a laboratory and analytical technique for quantifying tacrolimus and mycophenolic acid (MPA) from the Tasso-M20™ in human whole blood using bead-based impact-assisted extraction. Results: The sampled blood volume was accurate with estimated volumes within <2% of the expected 20 μl. Recovery using impact-assisted extraction was 73-87% for MPA and 100% for tacrolimus and was hematocrit-independent for both analytes. The LC-MS/MS assay is precise and accurate within the acceptance criteria of 15%. Conclusion: The sampling and extraction procedures allowed for accurate quantification of tacrolimus and MPA. Exploration of abuse scenarios identified important education points for patients conducting home-based sample collections in the future.

Introduction: High tacrolimus intrapatient variability is associated with poor outcomes following transplantation. A commonly hypothesized cause of this variability is medication non-adherence, but this has not been conclusively demonstrated. Research Question: The purpose of this study was to evaluate the relationship between medication adherence and tacrolimus intrapatient variability. Design: This was a retrospective cohort study of kidney transplant recipients. Adherence was assessed at the 12-month clinic visit as a composite of patient self-report, pharmacist assessment, and lab monitoring frequency. Tacrolimus intrapatient variability was calculated as the coefficient of variation (CV). Linear regression and receiver operating curve (ROC) analysis were used to assess the relationship between adherence and CV. Results: Nonadherence was identified in 37.5% of patients. The median CV was 27.1% for adherent patients and 29.8% for non-adherent patients ( P = 0.051). In the multivariable analysis, the only significant predictor of CV was the incidence of dose changes ( P = 0.002). ROC analysis demonstrated poor discriminant power with an AUC of 0.597. Discussion: The results fail to support a clinically meaningful relationship between medication adherence and tacrolimus CV. There is very little evidence at this time that adherence is the primary contributing factor to tacrolimus intrapatient variability and, by extension, that CV can be used as a surrogate for adherence.

Study Objective: This study investigated the effect of CYP3A5 phenotype on time in therapeutic range (TTR) of tacrolimus post-transplant in pediatric patients., Design and Data Source: This retrospective study assessed medical records of pediatric kidney and heart recipients with available CYP3A5 genotype for tacrolimus dosing, troughs, and the clinical events (biopsy-proven acute rejection [BPAR] and de novo donor-specific antibodies [dnDSA])., Measurements and Main Results: The primary outcome, mean TTR in the first 90 days post-transplant, was 9.0% (95% CI: -16.1, -1.9) lower in CYP3A5 expressers (p = 0.014) when adjusting for time to therapeutic concentration and organ type. There was no difference between CYP3A5 phenotypes in time to the first clinical event using TTR during the first 90 days. When applying TTR over the first year, there was a significant difference in event-free survival (EFS) which was 50.0% for CYP3A5 expressers/TTR < 35%, 45.5% for expressers/TTR ≥ 35%, 38.1% for nonexpressers/TTR < 35%, and 72.9% for nonexpressers/TTR ≥ 35% (log-rank p = 0.03). A post hoc analysis of EFS identified CYP3A5 expressers had lower EFS compared to nonexpressers in patients with TTR ≥ 35% (p = 0.04) but no difference among patients with TTR < 35% (p = 0.6)., Conclusions: The relationship between TTR and CYP3A5 phenotype suggests that achieving a TTR ≥ 35% during the first year may be a modifiable factor to attenuate the risk of BPAR and dnDSA., (© 2021 Pharmacotherapy Publications, Inc.)

Background: Currently, there is limited literature evaluating rATG induction dosing and incidence of opportunistic viral infections when using steroid-free maintenance immunosuppression., Methods: This single-center, retrospective, study compared high rATG (>4.5 mg/kg) versus low (<4.5 mg/kg) induction dosing and the overall incidence of early opportunistic viral infection at 180 days in the setting of maintenance immunosuppression consisting of tacrolimus, mycophenolate, rapid steroid withdrawal, and a tiered antiviral prevention strategy based on donor-recipient Cytomegalovirus (CMV) serostatus., Results: A total of 209 patients were included; 76 patients received low-dose and 133 patients received high-dose rATG. Incidence of overall opportunistic viral infection occurred more frequently in patients who received high compared to low dose (29.8% vs 25% p = .030). Incidence of CMV infection was also significantly increased in the high-dose group (31.6% vs 18.4% p = .039). In a multivariable model, rATG dose, as a continuous variable, remained a significant independent predictor of infection along with CMV risk (OR 1.46, 95% CI 1.02-2.09) controlling for age and CMV risk. There were no differences in graft-related outcomes at 180 days., Conclusion: Higher cumulative rATG induction dose was associated with increased incidence of opportunistic viral infections, in the setting of a steroid-free maintenance immunosuppression in the early post-transplant period., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Tacrolimus therapy in solid organ transplant (SOT) recipients is challenging due to its narrow therapeutic window and pharmacokinetic variability both between patients and within a single patient. Intrapatient variability (IPV) of tacrolimus trough concentrations has become a novel marker of interest for predicting transplant outcomes. The purpose of this review is to evaluate the association of tacrolimus IPV with graft and patient outcomes and identify interventions to improve IPV in SOT recipients., Methods: A systematic review of the literature was performed using PubMed and Embase from database inception to September 20, 2020. Studies were eligible only if they evaluated an association between tacrolimus IPV and transplant outcomes. Both pediatric and adult studies were included. Measures of variability were limited to standard deviation, coefficient of variation, and time in therapeutic range., Results: Forty-four studies met the inclusion criteria. Studies were published between 2008 and 2020 and were observational in nature. Majority of data were published in adult kidney transplant recipients and identified an association with rejection, de novo donor specific antibody (dnDSA) formation, graft loss, and patient survival. Evaluation of IPV-directed interventions was limited to small preliminary studies., Conclusions: High tacrolimus IPV has been associated with poor outcomes including acute rejection, dnDSA formation, graft loss, and patient mortality in SOT recipients. Future research should prospectively explore IPV-directed interventions to improve transplant outcomes., (© 2020 Pharmacotherapy Publications, Inc.)

Objective: To evaluate statin use in the U.S. before and after the 2015 American Diabetes Association position statement, which expanded statin therapy recommendations to include all adults 40-75 years old with diabetes., Research Design and Methods: The National Health and Nutrition Examination Survey (NHANES) was used to obtain a representative sample. The difference-in-differences technique determined the impact of the recommendation on the proportion of people with diabetes for whom statin therapy was newly recommended., Results: Among people with diabetes, the change in statin use in people without atherosclerotic cardiovascular disease (ASCVD) risk factors, controlling for change among people with ASCVD/risk factors, was 6.6% ( P = 0.388). In the adjusted analysis, overt ASCVD, age, Black race, health insurance, a place for routine care, and total cholesterol were significantly associated with statin use ( P < 0.05)., Conclusions: The most recent change in statin recommendations had minimal impact on the proportion of patients receiving a statin., (© 2020 by the American Diabetes Association.)

Background: Reduction in donor-specific antibody (DSA) has been associated with improved renal allograft survival after antibody-mediated rejection (AMR). These observations have not been separately analyzed for early and late AMR and mixed acute rejection (MAR). The purpose of this study was to evaluate long-term responses to proteasome inhibitor-based therapy for 4 rejection phenotypes and to determine factors that predict allograft survival., Methods: Retrospective cohort study evaluating renal transplant recipients with first AMR episodes treated with proteasome inhibitor-based therapy from January 2005 to July 2015., Results: A total of 108 patients were included in the analysis. Immunodominant DSA reduction at 14 days differed significantly (early AMR 79.6%, early MAR 54.7%, late AMR 23.4%, late MAR 21.1%, P < 0.001). Death-censored graft survival (DCGS) differed at 3 years postrejection (early AMR 88.3% versus early MAR 77.8% versus late AMR 56.7% versus late MAR 54.9%, P = 0.02). Multivariate analysis revealed that immunodominant DSA reduction > 50% at 14 days was associated with improved DCGS (odds ratio, 0.12, 95% CI, 0.02-0.52, P = 0.01)., Conclusions: In summary, significant differences exist across rejection phenotypes with respect to histological and DSA responses. The data suggest that DSA reduction may be associated with improved DCGS in both early and late AMR.

Calcineurin inhibitors, the primary immunosuppressive therapy used to prevent alloreactivity of transplanted organs, have a narrow therapeutic index. Currently, treatment is individualized based on clinical assessment of the risk of rejection or toxicity guided by trough concentration monitoring. Advances in immune monitoring have identified potential markers that may have value in understanding calcineurin inhibitor pharmacodynamics. Integration of these markers has the potential to complement therapeutic drug monitoring. Existing pharmacokinetic-pharmacodynamic (PK-PD) data is largely limited to correlation between the biomarker and trough concentrations at single time points. Immune related gene expression currently has the most evidence supporting PK-PD integration. Novel biomarker-based approaches to pharmacodynamic monitoring including development of enhanced PK-PD models are proposed to realize the full clinical benefit.

Cannabidiol (CBD), a major purified nonpsychoactive component of cannabis with anticonvulsant properties, was approved by the U.S. Food and Drug Administration (FDA) in June 2018 as an adjuvant treatment for refractory epilepsy (Epidiolex; GW Pharmaceuticals). CBD is metabolized by cytochrome P450 (CYP)3A4 and CYP2C19 with a growing body of evidence suggesting it is also a potent inhibitor of these pathways. We report for the first time a significant drug-drug interaction between the purified CBD product and tacrolimus. A participant in a CBD clinical trial for epilepsy who was also receiving tacrolimus showed an approximately 3-fold increase in dose-normalized tacrolimus concentrations while receiving 2000-2900 mg/day of CBD. Our report delineates an important concern for the transplant community with the increasing legalization of cannabis and advent of an FDA-approved CBD product. Larger studies are needed to better understand the impact of this drug-drug interaction in solid organ transplant recipients., (© 2019 The American Society of Transplantation and the American Society of Transplant Surgeons.)

The purpose of this study was to determine the intrapatient (within the same patient) variability of tacrolimus in adherent patients. Daily tacrolimus trough levels were obtained at home using dried blood spot technology in kidney and liver transplant recipients. Patients were randomized to receive 3 formulations of tacrolimus, each for two 1-week periods. Adherence was monitored by patient diary, pill counts, and use of the Medication Event Monitoring System (MEMS). Variability was quantified as the coefficient of variation (CV). Comparison of CV between groups was by independent t test or one-way ANOVA as appropriate. The population was found to be adherent with a rate of 99.9% with a mean interval between the evening and morning dose of tacrolimus of 11.86 hours. The median CV for the entire population was 15.2% (range 4.8%-110%). There were no differences in CV by allograft type or tacrolimus formulation. The multivariate analysis did not identify any demographic characteristics associated with a CV > 30%. In a highly adherent population, tacrolimus did not display high intrapatient variability. Given the association between IPV and poor allograft outcomes, future studies are needed to quantitate the influence of adherence and establish target IPV goals., (© 2018 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Starting in 2015, the American Society of Transplantation Psychosocial Community of Practice, with representatives of the Transplant Pharmacy Community of Practice, convened a taskforce to develop a white paper that focused on clinically practical, evidenced-based interventions that transplant centers could implement to increase adherence to medication and behavioral recommendations in adult solid organ transplant recipients. The group focused on what centers could do in their daily routines to implement best practices to increase adherence in adult transplant recipients. We developed a list of strategies using available resources, clinically feasible methods of screening and tracking adherence, and activities that ultimately empower patients to improve their own self-management. We limited the target population to adults because they predominate the research, and because adherence issues differ in pediatric patients, given the necessary involvement of parents/guardians. We also examined broader multilevel areas for intervention including provider and transplant program practices. Ultimately, the task force aims to foster greater recognition, discussion, and solutions required for implementing practical interventions targeted at improving adherence., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The endeavor to study desensitization in kidney transplantation has not been matched by an effort to investigate strategies to prevent sensitization. In this study (NCT02437422), we investigated the safety, impact on sensitization, and pharmacokinetics of SANGUINATE (SG), a hemoglobin-based oxygen carrier, as a potential alternative to packed red blood cells (PRBC) in transplant candidates with end-stage renal disease (ESRD). Ten ESRD subjects meeting inclusion/exclusion (I/E) criteria were planned to receive three weekly infusions of SG (320 mg/kg). The study was stopped after five subjects were enrolled, and their data were analyzed after completing a follow-up period of 90 days. Two subjects had elevated troponin I levels in setting of SG infusion, one of which was interpreted as a non-ST elevation myocardial infarction. All other adverse events were transient. SG pharmacokinetic analysis showed mean (SD) C max , T max , AUC, and half-life of 4.39 (0.69) mg/mL, 2.42 (0.91) hours, 171.86 (52.35) mg h/mL, and 40.60 (11.96) hours, respectively. None of the subjects developed new anti-HLA antibodies following SG infusion and throughout the study period. In conclusion, SG is a potential alternative to PRBCs in ESRD patients considered for kidney transplantation as it was not associated with humoral sensitization. Larger studies in highly sensitized patients are required to further evaluate for potential safety signals., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Severe obesity has been shown to limit access to renal transplantation in patients with end-stage renal disease (ESRD). Laparoscopic sleeve gastrectomy (LSG) has been performed in the ESRD population to assist in achieving waitlist and transplant eligibility. Little is known about how LSG impacts the bioequivalence of tacrolimus products and immunosuppression pharmacokinetics., Methods: This was a prospective, open-label, single-dose, crossover, two-period pharmacokinetic (PK) study. The purpose of this study was to assess single-dose PK of immediate-release tacrolimus (IR-TAC), extended-release tacrolimus (ER-TAC), and mycophenolic acid (MPA) in adult ESRD patients post-LSG., Results: Twenty-three subjects were included in the 24-hour PK assessments. The ratio of geometric means between ER-TAC and IR-TAC was 103.5% (90% CI; 89.6%-119.6%) for AUC 0-24 and 92.5% (90% CI; 80.4%-106.4%) for C max . PK parameters were similar between ER-TAC and IR-TAC, except for C min (P=.004) and C max (P=.04). MPA AUC 0-24 was similar when given with either ER-TAC or IR-TAC (P=.32). Patients expressing CYP3A5*1 genotypes had lower tacrolimus AUC 0-24 values vs those with CYP3A5*3/*3 (IR-TACP<.001; ER-TACP=.008). Genotype did not impact MPA PK., Conclusion: Dose modification of immunosuppressants post-LSG may not be necessary aside from standard therapeutic drug monitoring., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)