Immunosuppression-Free Life after Pediatric Liver Transplant: A Case-Control Study from the Society of Pediatric Liver Transplant (SPLIT) Registry.

OBJECTIVE: To compare long-term outcomes of pediatric liver transplant (LT) recipients off immunosuppression (IS) with matched controls on IS using data from the Society of Pediatric Liver Transplant (SPLIT) registry. STUDY DESIGN: This was a retrospective case-control study. SPLIT participants <18 years of age, ≥4 years after isolated LT, and off IS for ≥1 year (cases) were age- and sex-matched 1:2 to patients with the same primary diagnosis and post-LT follow-up duration (controls). Primary outcomes included retransplantation, allograft rejection, IS comorbidities, and prevalence of SPLIT-derived composite ideal outcome (c-IO) achieved at the end of the follow-up period. Differences were compared using multiple linear regression for continuous outcomes and logistic regression for dichotomous data. RESULTS: The study cohort was composed of 33 cases (42.4% male, 60.6% biliary atresia, median age at LT of 0.7 [P25, P75, 0.5, 1.6] years, median IS withdrawal time of 9 [P25, P75, 6, 12] years after LT) and 66 age- and sex-matched controls. No cases required retransplantation. Cases and controls had similar growth parameters, laboratory values, calculated glomerular filtration rates, rates of post-transplant lymphoproliferative disease, graft rejection, and attainment of c-IO. CONCLUSIONS: No differences in allograft rejection rates, IS complications, or c-IO prevalence were seen between SPLIT patients off IS and age- and sex-matched controls remaining on IS. Discontinuation of IS most commonly occurred in the context of rigorously designed IS withdrawal trials. The available sample size was small, affecting generalizability to the broader pediatric LT population.

An appraisal of technical variant grafts compared to whole liver grafts in pediatric liver transplant recipients: Multicenter analysis from the SPLIT registry.

BACKGROUND: Shortages of liver allografts for children awaiting transplantation have led to high LT waitlist mortality. Prior studies have shown that usage of TVG can reduce waiting time and waitlist mortality, but their use is not universal. We sought to compare patient and graft survival between WLG and TVG and to identify potential associated risk factors in a contemporary pediatric LT cohort. METHODS: We performed a retrospective analysis of patient survival, graft survival, and biliary and vascular complications for LT recipients <18 years old entered into the Society of Pediatric Liver Transplantation prospective multicenter database. RESULTS: Of 1839 LT recipients, 1029 received a WLG and 810 received a TVG from either a LD or a DD. There was no difference in patient survival or graft survival by graft type. Three-year patient survival and graft survival were 96%, 93%, and 96%, and 95%, 89%, and 92% for TVG-LD, TVG-DD, and WLG, respectively. Biliary complications were more frequent in TVG. Hepatic artery thrombosis was more frequent in WLG. Multivariate analysis revealed primary diagnosis was the only significant predictor of patient survival. Predictors for graft survival included time-dependent development of biliary and vascular complications. CONCLUSIONS: There were no significant differences in patient and graft survival based on graft types in this North American multi-center pediatric cohort. Widespread routine use of TVG should be strongly encouraged to decrease mortality on the waitlist for pediatric LT candidates.

The improving Medication Adherence in Adolescents and young adults following Liver Transplantation (iMALT) multisite trial: Design and trial implementation considerations.

BACKGROUND/AIMS: Medication non-adherence is a leading cause of transplant rejection, organ loss, and death; yet no rigorous controlled study to date has shown compelling clinical benefits from an adherence-improving intervention. Non-adherent patients are less likely to participate in trials, and therefore, most studies enroll a majority of adherent patients who do not stand to benefit from the intervention, as they do not have the condition (non-adherence) under investigation. The improving Medication Adherence in adolescent Liver Transplant recipients trial specifically targets non-adherent patients to investigate whether a remote intervention to improve adherence results in reduced incidence of biopsy-confirmed rejection. METHODS: Improving Medication Adherence in adolescent Liver Transplant is a randomized single-blind controlled multisite, multinational National Institutes of Health-funded trial involving 13 pediatric transplant centers in the United States and Canada. An innovative, objective adherence biomarker-the Medication Level Variability Index, which is the standard deviation of a series of medication blood levels for each patient, is used to identify non-adherent patients at risk for rejection. The index is computed using electronic health record information for all potentially eligible patients based on repeated reviews of the entire clinic's roster. Identified patients, after consent, are randomized to intervention versus control (treatment as usual) arms. The remote intervention is delivered for 2 years by trained interventionists who reside in various locations in the United States. The primary outcome is the incidence of biopsy-confirmed acute cellular rejection, as confirmed by a majority vote of three pathologists who are masked to the study allocation and clinical information. DISCUSSION: Improving Medication Adherence in adolescent Liver Transplant includes several innovative design elements. The use of a validated, objective adherence index to survey a large cohort of transplant recipients allows the teams to avoid bias inherent in both convenience sampling and referral-based recruitment and enroll only patients whose computed index indicates substantially increased risk of rejection. The remote intervention paradigm helps to engage patients who are by definition hard to engage. The use of an objective, masked medical (rather than behavioral) outcome measure reduces the likelihood of biases related to clinical information and ensures broad acceptance by the field. Finally, monitoring for potential adverse events related to increased medication exposure due to the adherence intervention acknowledges that a successful intervention (increasing adherence) could have detrimental side effects via increased exposure to and potential toxicity of the medication. Such monitoring is almost never attempted in clinical trials evaluating adherence interventions.

Predictors of survival following liver transplantation for pediatric hepatoblastoma and hepatocellular carcinoma: Experience from the Society of Pediatric Liver Transplantation (SPLIT).

Management of unresectable pediatric hepatoblastoma (HB) and hepatocellular carcinoma (HCC) remains challenging. The Society of Pediatric Liver Transplantation (SPLIT) database was used to study survival predictors in pediatric liver transplantation (LT) for HB and HCC. Event-free survival (EFS), associated risk factors, and postoperative complications were studied in children requiring LT for HB/HCC at 16 SPLIT centers. Three-year EFS was 81% for HB (n = 157) and 62% for HCC (n = 18) transplants. Of HB transplants, 6.9% were PRETEXT II and 15.3% were POST-TEXT I/II. Tumor extent did not impact survival (p = NS). Salvage (n = 13) and primary HB transplants had similar 3-year EFS (62% versus 78%, p = NS). Among HCC transplants, 3-year EFS was poorer in older patients (38% in ≥8-year-olds vs 86% <8-year-olds) and those with larger tumors (48% for those beyond versus 83% within Milan criteria, p = NS). Risk of infection (HR 1.5, 95% CI 1.1-2.2, p = .02) and renal injury (HR 2.4, 95% CI 1.7-3.3, p < .001) were higher in malignant versus nonmalignant LT. Survival is favorable for pediatric HB and HCC LT, including outcomes after salvage transplant. Unexpected numbers of LTs occurred in PRE/POST-TEXT I/II tumors. Judicious patient selection is critical to distinguish tumors that are potentially resectable; simultaneously, we must advocate for patients with unresectable malignancies to receive organs.

Factors associated with improved patient and graft survival beyond 1 year in pediatric liver transplantation.

With advances in surgical techniques, medical management, and more equitable allocation systems, children who receive a liver transplantation (LT) today can expect remarkable outcomes early after LT. However, beyond 1 year after transplant, attrition rates have not improved. We reviewed two separate eras (Era 1: January 1995-June 2004 vs. Era 2: July 2004-March 2018) of the Society of Pediatric Liver Transplantation registry to explore the evolution and associated factors contributing to late graft loss (LGL) and late mortality (LM). The fraction of long-term pediatric LT recipients surviving after 1 year with their first graft significantly improved (81.5% in Era 1 vs. 85.7% in Era 2; p < 0.0001). This improvement occurred despite significant changes in patient selection toward higher risk populations (p < 0.001) and without notable improvement in perioperative complications such as hepatic artery thrombosis (p = 0.24) and early posttransplant reoperation (p = 0.94) that have historically contributed to poor late-allograft outcomes. Improved outcomes were associated with changes in patient characteristics and perioperative practices, which subsequently impacted both early post-LT complications as well as other sequalae known to contribute to adverse events in long-term pediatric LT recipients. In conclusion, despite significant changes in patient selection toward higher risk populations, and without notable improvement in several perioperative complications known to contribute to poor late-allograft outcomes, significant improvements in LGL and a trend toward improvement in LM was seen in a more contemporary cohort of children receiving an LT.

Organ-Specific Comorbidities Are Associated With Distinct Complications After Liver Transplantation for Biliary Atresia.

Although transplant outcomes for biliary atresia (BA) have improved, there are few data to predict the risk of specific posttransplant complications. We therefore defined the impact of comorbidities in BA on posttransplant outcomes. Patients enrolled in the Society of Pediatric Liver Transplantation registry from 2011 to 2019 (n = 1034) were grouped by comorbidities of >1.0% incidence: any supplemental feeding, dialysis, other abdominal surgery (not Kasai portoenterostomy [KPE]), hepatopulmonary syndrome, and cardiac disease requiring intervention. Demographic and outcome data were compared using the Kruskal-Wallis, chi-square, and log-rank tests. Cox proportional hazards models and binary logistic regression were performed for modeling. Patients with BA with comorbidities comprised 77% (n = 799) of our cohort and had evidence of greater medical acuity, including higher calculated Pediatric End-Stage Liver Disease scores and hospitalizations in the intensive care unit before transplant (P < 0.001 for both) versus those without comorbidities. After transplant, patients with BA with comorbidities had more graft loss (P = 0.02), longer initial hospitalization and intubation (P < 0.001 for both), and increased rates of reoperation (P = 0.001) and culture-proven infection (P < 0.001) within 30 days after transplant. Only patients with BA with comorbidities on supplemental feed had increased rates of patient death (P = 0.02). Multivariate analysis identified lower z weight and higher creatinine as risk factors for graft and patient loss in patients with BA with comorbidities. Prior KPE was protective against culture-proven infection and vascular complications within 30 and 90 days, respectively. Patients with BA with comorbidities have evidence of higher medical acuity at transplant and reduced graft survival; however, they overall did not experience greater incidence of patient death. Our data provide organ-system-specific data to risk-stratify patients with BA and posttransplant outcomes.

Outcomes following liver transplantation in young infants: Data from the SPLIT registry.

Liver transplantation (LT) in young patients is being performed with greater frequency. We hypothesized that objective analysis of pre-, intra-, and postoperative events would help understand contributors to successful outcomes and guide transplant decision processes. We queried SPLIT registry for pediatric transplants between 2011 and 2018. Outcomes were compared for age groups: 0-<3, 3-<6, 6-<12 months, and 1-<3 years (Groups A, B, C, D respectively) and by weight categories: <5, 5-10, >10 kg; 1033 patients were available for analysis. Cholestatic disease and fulminant failure were highest in group A and those <5 kg; and biliary atresia in group C (72.8%). Group A had significantly higher life support dependence (34.6%; P < .001), listing as United Network for Organ Sharing status 1a/1b (70.4%; P < .001), and shortest wait times (P < .001). The median (interquartile range) for international normalized ratio and bilirubin were highest in group A (3.0 [2.1-3.9] and 16.7 [6.8-29.7] mg/dL) and those <5 kg (2.6 [1.8-3.4] and 13.5 [3.0-28.4] mg/dL). A pediatric end -stage liver disease score ≥40, postoperative hospital stays, rejection, and nonanastomotic biliary strictures were highest in group A with lowest survival at 93.1%. Infants 0 to <3 months and those <5 kg need more intensive care with lower survival and higher complications. Importantly, potential LT before reaching status 1a/1b and aggressive postoperative management may positively influence their outcomes.

Approaches to Research Determination of Late Acute Cellular Rejection in Pediatric Liver Transplant Recipients.

A central pathology or site reading of biopsy slides is used in liver transplant clinical trials to determine rejection. We evaluated interrater reliability of readings of "rejection or not" using digitized slides from the Medication Adherence in Children who had a Liver Transplant (MALT) study. Four masked experienced pathologists read the digitized slides and then reread them after a study-specific histologic endpoint development program. Agreement was expressed throughout as a Kappa or Fleiss Kappa statistic (Ò¡). A Ò¡ > 0.6 was predefined as desirable. Readings were correlated with immunosuppressant adherence (the Medication Level Variability Index, [MLVI]), and maximal liver enzyme levels during the study period. Interrater agreement between site and central review in MALT, and between 4 pathologists later on, was low (Ò¡ = 0.44, Fleiss Ò¡ = 0.41, respectively). Following the endpoint development program, agreement improved and became acceptable (Ò¡ = 0.71). The final reading was better-aligned with maximal gamma-glutamyl transferase levels and MLVI as compared with the original central reading. We found substantial disagreement between experienced pathologists reading the same slides. A unique study-specific procedure improved interrater reliability to the point it was acceptable. Such a procedure may be indicated to increase reliability of histopathologic determinations in future research, and perhaps also clinically.

Improved Outcomes for Liver Transplantation in Patients with Biliary Atresia Since Pediatric End-Stage Liver Disease Implementation: Analysis of the Society of Pediatric Liver Transplantation Registry.

OBJECTIVE: To identify changes in demographics, outcomes, and risk factors for patient and graft loss in patients with biliary atresia undergoing liver transplantation since Pediatric End-Stage Liver Disease implementation (2002). STUDY DESIGN: Demographics and outcomes were compared between patients enrolled in the Society of Pediatric Liver Transplantation registry before (n = 547) and after (n = 1477) 2002. Kruskal-and χ2 Wallis tests identified significant differences between eras. Risk factors for patient and graft loss after 2002 were determined by Cox regression model analysis of time to event data. RESULTS: Significant patient differences after 2002 support increasing disease severity including more status 1 patients and those with a derived Model for End-Stage Liver Disease/Pediatric End-Stage Liver Disease score of greater than 30 awaiting transplant. Both patient and graft survival improved after 2002 from 90% to 97% and 81% to 90%, respectively (primary transplant; P < .0001). Significant differences in complications within 30 days included reduced relisting for transplant, rejection, culture-positive infection, repeat operation, hepatic artery thrombosis, portal vein thrombosis, and death/transplant before discharge. Multivariable analysis identified deceased technical variant vs whole graft and retransplantation predictive for patient death, hazard ratios of 4.041 and 8.308, respectively. Deceased technical variant vs whole graft (hazard ratio, 1.963) and donor age 0-5 months vs 1-17 years (hazard ratio, 5.525) were risk factors for graft loss. CONCLUSIONS: The overall outcomes of patients receiving liver transplantation for patients with biliary atresia have improved since 2002 despite evidence of increased disease severity at the time of transplant. Risk factors impacting post-transplant morbidity and mortality in patients with biliary atresia are now mainly surgical including donor variables.

The impact of caregiver post-traumatic stress and depressive symptoms on pediatric transplant outcomes.

PTSS as well as symptoms of depression have been reported in children who experience a serious medical adversity as well as their caretakers. The adverse effects of PTSS, when experienced by the patients, on medical outcomes have been clearly documented. However, the impact of those symptoms, if any, when experienced by the caretakers on child outcomes has not been investigated prospectively. We evaluated whether caregiver PTSS and depression symptoms predict adherence to medications and medical outcomes in a prospective multisite study. Four hundred children participated in MALT. Caretaker PTSS were assessed by the IES and depressive symptoms by CES-D. During 2 years of follow-up, the MLVI was used to determine adherence. Centrally read, biopsy-confirmed organ rejection was the primary medical outcome. IES scores were not associated with either adherence or rejection outcomes. In contrast, there were significant correlations between CES-D (depression) scores and lower adherence, r = .13, P < .001, and a trend toward higher scores on the CES-D among those whose children had experienced rejection, 12.4 (SD = 10.9) versus 9.1 (SD = 8.6), P = .077. Caregivers' PTSS were not a risk factor for poor child outcomes in this cohort, whereas depression symptoms were associated with non-adherence and possibly increased rates of rejection. Further study can validate if caregivers' depression as opposed to PTSS confers greater risk and should be a focus during the clinical care of medically ill children.

Society of pediatric liver transplantation: Current registry status 2011-2018.

BACKGROUND: SPLIT was founded in 1995 in order to collect comprehensive prospective data on pediatric liver transplantation, including waiting list data, transplant, and early and late outcomes. Since 2011, data collection of the current registry has been refined to focus on prospective data and outcomes only after transplant to serve as a foundation for the future development of targeted clinical studies. OBJECTIVE: To report the outcomes of the SPLIT registry from 2011 to 2018. METHODS: This is a multicenter, cross-sectional analysis characterizing patients transplanted and enrolled in the SPLIT registry between 2011 and 2018. All patients, <18 years of age, received a first liver-only, a combined liver-kidney, or a combined liver-pancreas transplant during this study period. RESULTS: A total of 1911 recipients from 39 participating centers in North America were registered. Indications included biliary atresia (38.5%), metabolic disease (19.1%), tumors (11.7%), and fulminant liver failure (11.5%). Greater than 50% of recipients were transplanted as either Status 1A/1B or with a MELD/PELD exception score. Incompatible transplants were performed in 4.1%. Kaplan-Meier estimates of 1-year patient and graft survival were 97.3% and 96.6%. First 30 days of surgical complications included reoperation (31.7%), hepatic artery thrombosis (6.3%), and portal vein thrombosis (3.2%). In the first 90 days, biliary tract complications were reported in 13.6%. Acute cellular rejection during first year was 34.7%. At 1 and 2 years of follow-up, 39.2% and 50.6% had normal liver tests on monotherapy (tacrolimus or sirolimus). Further surgical, survival, allograft function, and complications are detailed.

Rifampin Pharmacokinetics and Safety in Preterm and Term Infants.

Rifampin is active against methicillin-resistant staphylococcal species and tuberculosis (TB). We performed a multicenter, prospective pharmacokinetic (PK) and safety study of intravenous rifampin in infants of <121 days postnatal age (PNA). We enrolled 27 infants; the median (range) gestational age was 26 weeks (23 to 41 weeks), and the median PNA was 10 days (0 to 84 days). We collected 102 plasma PK samples from 22 of the infants and analyzed safety data from all 27 infants. We analyzed the data using a population PK approach. Rifampin PK was best characterized by a one-compartment model; drug clearance increased with increasing size (body weight) and maturation (PNA). There were no adverse events related to rifampin. Simulated weight and PNA-based intravenous dosing regimens administered once daily (<14 days PNA, 8 mg/kg; ≥14 days PNA, 15 mg/kg) in infants resulted in comparable exposures to adults receiving therapeutic doses of rifampin against staphylococcal infections and TB. (This study has been registered at ClinicalTrials.gov under identifier NCT01728363.).

Pharmacokinetics of ticarcillin-clavulanate in premature infants.

Ticarcillin-clavulanate covers a broad spectrum of pathogens that are common in premature infants. In infants <30 weeks gestational age, pharmacokinetic data to guide ticarcillin-clavulanate dosing are lacking. We enrolled 15 premature infants <30 weeks gestational age, determined pharmacokinetic parameters, and performed dosing simulations to determine optimal dosing for ticarcillin-clavulanate. The infants had a median (range) postnatal age (PNA) of 18 days (6-44 days) and gestational age of 25 weeks (23-28 weeks). Clearance was lower in infants with a PNA <14 days (0.050 L/kg/h [range 0.043-0.075]) compared with a PNA ≥14-45 days (0.078 L/kg/h [0.047-0.100]), consistent with maturation of renal function. Dosing simulations determined that ticarcillin 75 mg/kg q12h (PNA <14 days) or q8h (PNA ≥ 14-45 days) achieved the target exposure for organisms with a minimum inhibitory concentration ≤16 µ/mL in >90% of simulated infants. For highly resistant organisms (minimum inhibitory concentration 32 µg/mL), increased dosing frequency or extended infusion are necessary.

Predicting ideal outcome after pediatric liver transplantation: An exploratory study using machine learning analyses to leverage Studies of Pediatric Liver Transplantation Data.

Machine learning analyses allow for the consideration of numerous variables in order to accommodate complex relationships that would not otherwise be apparent in traditional statistical methods to better classify patient risk. The SPLIT registry data were analyzed to determine whether baseline demographic factors and clinical/biochemical factors in the first-year post-transplant could predict ideal outcome at 3 years (IO-3) after LT. Participants who received their first, isolated LT between 2002 and 2006 and had follow-up data 3 years post-LT were included. IO-3 was defined as alive at 3 years, normal ALT (<50) or GGT (<50), normal GFR, no non-liver transplants, no cytopenias, and no PTLD. Heat map analysis and RFA were used to characterize the impact of baseline and 1-year factors on IO-3. 887/1482 SPLIT participants met inclusion criteria; 334 had IO-3. Demographic, biochemical, and clinical variables did not elucidate a visual signal on heat map analysis. RFA identified non-white race (vs white race), increased length of operation, vascular and biliary complications within 30 days, and duct-to-duct biliary anastomosis to be negatively associated with IO-3. UNOS regions 2 and 5 were also identified as important factors. RFA had an accuracy rate of 0.71 (95% CI: 0.68-0.74), PPV = 0.83, and NPV = 0.70. RFA identified participant variables that predicted IO-3. These findings may allow for better risk stratification and personalization of care following pediatric liver transplantation.

Trajectory of adherence behavior in pediatric and adolescent liver transplant recipients: The medication adherence in children who had a liver transplant cohort.

Knowledge of the longterm trajectory of nonadherence to immunosuppressants can inform decisions regarding organ allocation, adherence monitoring, and intervention efforts. The Medication Adherence in Children Who Had a Liver Transplant (MALT) prospective multisite study followed 400 pediatric and adolescent liver transplant recipients for 2 years, using the Medication Level Variability Index to monitor adherence. We hypothesized that adherence is an unstable (fluctuating) phenomenon: that patients who are adherent in year 1 may become nonadherent in year 2, and vice versa. However, we also hypothesized that a majority (more than 50%) of nonadherent patients remain nonadherent over time. We further hypothesized that the longer nonadherence lasts, the higher the likelihood of adverse events (rejection). Finally, we explored the effect of socioeconomic factors on the evolution of adherence over time. Most (59.7%) of the MALT patients who were nonadherent in year 1 remained so in year 2; 18.5% of patients who were adherent in year 1 became nonadherent in year 2. Only 4.4% of patients who were adherent in both year 1 and year 2 had a rejection, compared with 22.9% of patients who were nonadherent during 1 of the years, and 34.9% of those who were nonadherent in both years (P < 0.001), establishing a "dose-dependent" effect of adherence on transplant outcomes. Single-parent households were associated with worsening adherence. Our results suggest that good baseline adherence does not guarantee adherence later on, that nonadherence is likely to persist in the absence of interventions, and that monitoring of adherence and interventions to improve it should be expected to last for years if transplant outcomes are to be improved. Liver Transplantation 24 80-88 2018 AASLD.

Pharmacokinetics of Clindamycin in Obese and Nonobese Children.

Although obesity is prevalent among children in the United States, pharmacokinetic (PK) data for obese children are limited. Clindamycin is a commonly used antibiotic that may require dose adjustment in obese children due to its lipophilic properties. We performed a clindamycin population PK analysis using data from three separate trials. A total of 420 samples from 220 children, 76 of whom had a body mass index greater than or equal to the 95th percentile for age, were included in the analysis. Compared to other metrics, total body weight (TBW) was the most robust measure of body size. The final model included TBW and a sigmoidal maturation relationship between postmenstrual age (PMA) and clearance (CL): CL (liters/hour) = 13.8 × (TBW/70)0.75 × [PMA2.83/(39.52.83+PMA2.83)]; volume of distribution (V) was associated with TBW, albumin (ALB), and alpha-1 acid glycoprotein (AAG): V (liters) = 63.6 × (TBW/70) × (ALB/3.3)-0.83 × (AAG/2.4)-0.25 After accounting for differences in TBW, obesity status did not explain additional interindividual variability in model parameters. Our findings support TBW-based dosing for obese and nonobese children.

Recruiting a representative sample in adherence research-The MALT multisite prospective cohort study experience.

Medication adherence is an important determinant of transplant outcomes. Attempts to investigate adherence are frequently undermined by selection bias: It is very hard to recruit and retain non-adherent patients in research efforts. This manuscript presents recruitment strategies and results from the MALT (Medication Adherence in children who had a Liver Transplant) multisite prospective cohort study. MALT sites recruited 400 pediatric liver transplant patients who agreed to be followed for 2 years. The primary purpose was to determine whether a marker of adherence, the Medication Level Variability Index (MLVI), predicts rejection outcomes. The present manuscript describes methods used in MALT to ensure that a representative sample was recruited, and presents detailed recruitment results. MALT sites were able to recruit a nationally representative sample, as determined by a comparison between the MALT cohort and a national sample of transplant recipients. Strategies that helped ensure that the sample was representative included monitoring of the outcome measure in comparison with a national sample, drastically limiting patient burden, and specific recruitment methods. We discuss the importance of a representative sample in adherence research and recommend that future efforts to study adherence pay special attention to sample characteristics.

Safety and efficacy of sodium nitroprusside during prolonged infusion in pediatric patients.

OBJECTIVE: Sodium nitroprusside is a direct-acting vasodilator used to lower blood pressure in the operating room and ICU. The efficacy of sodium nitroprusside has been analyzed in few pediatric randomized trials. This study assesses the efficacy and safety of sodium nitroprusside following at least 12 hours of IV infusion in children. DESIGN: Randomized, double-blind withdrawal to placebo study. SETTING: ICUs. PATIENTS: Pediatric patients younger than 17 years. INTERVENTIONS: Following 12-24 hours of open-label sodium nitroprusside titration, a blinded infusion of sodium nitroprusside or placebo was administered (at the stable rate used at the end of the open-label phase) for up to 30 minutes. MEASUREMENTS AND MAIN RESULTS: The primary efficacy measure was whether control of mean arterial blood pressure was lost, that is, increased above ambient baseline for two consecutive minutes during the blinded phase. The proportion of patients who lost mean arterial blood pressure control in the placebo group (15/19; 79%) was significantly different than those in the sodium nitroprusside group (9/20; 45%) (p = 0.048). Three patients experienced rebound hypertension during the blinded phase, and all were in the placebo group. Serious adverse event rates were low (7/52; 13%), and in only one patient was the serious adverse event determined to be related to sodium nitroprusside by the site investigator. Fourteen patients (27%) had whole blood cyanide levels above 0.5 µg/mL, with high correlation (0.7) between infusion rate and cyanide levels, but there were few clinical signs of cyanide toxicity. CONCLUSIONS: Sodium nitroprusside is efficacious in maintaining mean arterial blood pressure control in children following a 12-hour infusion. Although a high proportion of patients were found to have elevated cyanide levels, toxicity was not observed.

Medication level variability index predicts rejection, possibly due to nonadherence, in adult liver transplant recipients.

Nonadherence to immunosuppressants may play a role in late rejection in liver transplant recipients. In children, emerging data suggest that adherence can be measured through the computation of the standard deviation (SD) of consecutive blood levels of tacrolimus, which results in a number that reflects the degree of variability between individual measures: the medication level variability index (MLVI). A higher MLVI value means erratic immunosuppression, likely due to less adherence. Data on this method are limited for adults. We obtained data from the medical charts of 150 randomly selected adult recipients. The MLVI was significantly higher for patients who had biopsy-confirmed rejection (mean MLVI = 3.8, SD = 3.2) versus the rest of the cohort (mean MLVI = 2.3, SD = 1.5, P = 0.003), and it was significantly higher for patients who suffered rejection versus patients whose biopsy sample was not read as rejection (mean MLVI = 2.6, SD = 1.6, P = 0.008). The MLVI was associated with rejection and predicted its occurrence. A threshold MLVI of 2.0 resulted in 77% sensitivity and 60% specificity in predicting rejection; a threshold of 1.8 resulted in a sensitivity of 92% and a specificity of 48%. The area under the curve in a receiver operating characteristic curve analysis was 0.71 (95% CI = 0.61-0.81). In conclusion, the MLVI is associated with and can predict rejection, possibly related to nonadherence, in adult liver transplant recipients.

Physiologically-based pharmacokinetic modeling of pantoprazole to evaluate the role of CYP2C19 genetic variation and obesity in the pediatric population.

Pantoprazole is a proton pump inhibitor indicated for the treatment of gastroesophageal reflux disease, a condition that disproportionately affects children with obesity. Appropriately dosing pantoprazole in children with obesity requires understanding the body size metric that best guides dosing, but pharmacokinetic (PK) trials using traditional techniques are limited by the need for larger sample sizes and frequent blood sampling. Physiologically-based PK (PBPK) models are an attractive alternative that can account for physiologic-, genetic-, and drug-specific changes without the need for extensive clinical trial data. In this study, we explored the effect of obesity on pantoprazole PK and evaluated label-suggested dosing in this population. An adult PBPK model for pantoprazole was developed using data from the literature and accounting for genetic variation in CYP2C19. The adult PBPK model was scaled to children without obesity using age-associated changes in anatomical and physiological parameters. Lastly, the pediatric PBPK model was expanded to children with obesity. Three pantoprazole dosing strategies were evaluated: 1 mg/kg total body weight, 1.2 mg/kg lean body weight, and US Food and Drug Administration-recommended weight-tiered dosing. Simulated concentration-time profiles from our model were compared with data from a prospective cohort study (PAN01; NCT02186652). Weight-tiered dosing resulted in the most (>90%) children with pantoprazole exposures in the reference range, regardless of obesity status or CYP2C19 phenotype, confirming results from previously published population PK models. PBPK models may allow for the efficient study of physiologic and developmental effects of obesity on PK in special populations where clinical trial data may be limited.