Sildenafil exposure and hemodynamic effect after stage II single-ventricle surgery

Prediction of Pediatric Pharmacokinetics for CYP3A4 Metabolized Drugs: Comparison of the Performance of Two Hepatic Ontogeny Within a Physiologically Based Pharmacokinetic Model

The rapid growth in the use of pediatric physiologically based pharmacokinetic (PBPK) models, particularly for regulatory applications, has focused emphasis on model verification and ensuring system parameters are robust, including how these change with age. Uncertainty remains regarding the ontogeny of some enzymes and transporters, in this study 2 published ontogeny profiles for hepatic CYP3A4 were compared. Clinical pharmacokinetic data on 4 intravenously administered CYP3A4 substrates (alfentanil, fentanyl, midazolam, and sildenafil) used across the pediatric age range was collected from the literature. The PBPK models were verified in the adult population and then used to compare the Salem and a modified Upreti ontogeny profiles for CYP3A4 in terms of parent drug clearance and area under the curve from birth onward. Overall, the modified Upreti ontogeny profile resulted in 15 out of 17 age-related predictions within 2-fold and 12 out of 17 predictions within 1.5-fold ranges of observed values, for the Salem ontogeny these values were 12 out of 17 and 8 out of 17, respectively. The Upreti ontogeny profile performed better than Salem, average fold error and absolute average fold error were 1.14 and 1.35 compared to 1.56 and 1.90, respectively. Identifying the optimal CYP3A4 ontogeny is important for regulatory use of PBPK especially given the number of drugs cleared by this enzyme. This study broadens the evidence from previous studies that Upreti is more favorable than Salem, but further work is needed especially in the neonatal and early infant age range.

Current Status of Pharmacokinetic Research in Children: A Systematic Review of Clinical Trial Records

BACKGROUND

Many medications have different pharmacokinetics in children than in adults. Knowledge about the safety and efficacy of medications in children requires research into the pharmacokinetic profiles of children's medicines. By analysing registered clinical trial records, this study determined how frequently pharmacokinetic data is gathered in paediatric drug trials.

METHODS

We searched for the pharmacokinetic data from clinical trial records for preterm infants and children up to the age of 16 from January 2011 to April 2022. The records of trials involving one or more drugs in preterm infants and children up to the age of 16 were examined for evidence that pharmacokinetic data would be collected.

RESULTS

In a total of 1483 records of interventional clinical trials, 136 (9.17%) pharmacokinetic data involved adults. Of those 136 records, 60 (44.1%) records were pharmacokinetics trials involving one or more medicines in children up to the age of 16. 20 (33.3 %) in America, followed by 19 (31.6 %) in Europe. Most trials researched medicines in the field of infection or parasitic diseases 20 (33.3%). 27 (48.2%) and 26 (46.4%) trials investigated medicines that were indicated as essential medicine.

CONCLUSION

The pharmacokinetic characteristics of children's drugs need to be better understood. The current state of pharmacokinetic research appears to address the knowledge gap in this area adequately. Despite slow progress, paediatric clinical trials have experienced a renaissance as the significance of paediatric trials has gained international attention. The outcome of paediatric trials will have an impact on children's health in the future. In recent years, the need for greater availability and access to safe child-size pharmaceuticals has received a lot of attention.

Medical Therapies for Heart Failure in Hypoplastic Left Heart Syndrome

Significant surgical and medical advances over the past several decades have resulted in a growing number of infants and children surviving with hypoplastic left heart syndrome (HLHS) and other congenital heart defects associated with a single systemic right ventricle (RV). However, cardiac dysfunction and ultimately heart failure (HF) remain the most common cause of death and indication for transplantation in this population. Moreover, while early recognition and treatment of single ventricle-related complications are essential to improving outcomes, there are no proven therapeutic strategies for single systemic RV HF in the pediatric population. Importantly, prototypical adult HF therapies have been relatively ineffective in mitigating the need for cardiac transplantation in HLHS, likely due to several unique attributes of the failing HLHS myocardium. Here, we discuss the most commonly used medical therapies for the treatment of HF symptoms in HLHS and other single systemic RV patients. Additionally, we provide an overview of potential novel therapies for systemic ventricular failure in the HLHS and related populations based on fundamental science, pre-clinical, clinical, and observational studies in the current literature.

Bosentan combined with sildenafil in the treatment of COPD patients with pulmonary arterial hypertension

OBJECTIVE

To explore the impacts of bosentan combined with sildenafil on chronic obstructive pulmonary disease (COPD) patients with pulmonary arterial hypertension (PAH).

METHODS

From April 2019 to October 2020, 90 COPD patients with PAH diagnosed in our hospital were recruited and divided into groups A and B. The patients in group A (50 cases) were treated with bosentan combined with sildenafil, and the patients in group B (40 cases) were administered bosentan combined with iloprost solution for inhalation. The PAH conditions, the heart rates (HR), the cardiac function, the pulmonary function, the blood gas indexes, the inflammatory factor expressions, the incidences of adverse reactions, the overall response rates (ORR), and the patient satisfaction levels were determined or evaluated.

RESULTS

Compared with group B, the patients in group A had better recovered PAH, HR, cardiac function, pulmonary function, and blood gas indexes, lower inflammatory factor expression levels and a lower incidence of adverse reactions, as well as higher ORR and higher satisfaction levels.

CONCLUSION

Bosentan combined with sildenafil can reduce pulmonary artery pressure and promote the recovery of cardiopulmonary function in COPD patients with PAH.

Pediatric Pulmonary Hypertension: Definitions, Mechanisms, Diagnosis, and Treatment

Pediatric pulmonary hypertension (PPH) is a multifactorial disease with diverse etiologies and presenting features. Pulmonary hypertension (PH), defined as elevated pulmonary artery pressure, is the presenting feature for several pulmonary vascular diseases. It is often a hidden component of other lung diseases, such as cystic fibrosis and bronchopulmonary dysplasia. Alterations in lung development and genetic conditions are an important contributor to pediatric pulmonary hypertensive disease, which is a distinct entity from adult PH. Many of the causes of pediatric PH have prenatal onset with altered lung development due to maternal and fetal conditions. Since lung growth is altered in several conditions that lead to PPH, therapy for PPH includes both pulmonary vasodilators and strategies to restore lung growth. These strategies include optimal alveolar recruitment, maintaining physiologic blood gas tension, nutritional support, and addressing contributing factors, such as airway disease and gastroesophageal reflux. The outcome for infants and children with PH is highly variable and largely dependent on the underlying cause. The best outcomes are for neonates with persistent pulmonary hypertension (PPHN) and reversible lung diseases, while some genetic conditions such as alveolar capillary dysplasia are lethal. © 2021 American Physiological Society. Compr Physiol 11:2135-2190, 2021.

Heart failure in single right ventricle congenital heart disease: physiological and molecular considerations

Because of remarkable surgical and medical advances over the past several decades, there are growing numbers of infants and children living with single ventricle congenital heart disease (SV), where there is only one functional cardiac pumping chamber. Nevertheless, cardiac dysfunction (and ultimately heart failure) is a common complication in the SV population, and pharmacological heart failure therapies have largely been ineffective in mitigating the need for heart transplantation. Given that there are several inherent risk factors for ventricular dysfunction in the setting of SV in addition to probable differences in molecular adaptations to heart failure between children and adults, it is perhaps not surprising that extrapolated adult heart failure medications have had limited benefit in children with SV heart failure. Further investigations into the molecular mechanisms involved in pediatric SV heart failure may assist with risk stratification as well as development of targeted, efficacious therapies specific to this patient population. In this review, we present a brief overview of SV anatomy and physiology, with a focus on patients with a single morphological right ventricle requiring staged surgical palliation. Additionally, we discuss outcomes in the current era, risk factors associated with the progression to heart failure, present state of knowledge regarding molecular alterations in end-stage SV heart failure, and current therapeutic interventions. Potential avenues for improving SV outcomes, including identification of biomarkers of heart failure progression, implications of personalized medicine and stem cell-derived therapies, and applications of novel models of SV disease, are proposed as future directions.

Efficacy of phosphodiesterase type 5 inhibitors in univentricular congenital heart disease: the SV-INHIBITION study design

Aims

In univentricular hearts, selective lung vasodilators such as phosphodiesterase type 5 (PDE5) inhibitors would decrease pulmonary resistance and improve exercise tolerance. However, the level of evidence for the use of PDE5 inhibitors in patients with a single ventricle (SV) remains limited. We present the SV‐INHIBITION study rationale, design, and methods.

Methods and results

The SV‐INHIBITION trial is a nationwide multicentre, randomized, double blind, placebo‐controlled, Phase III study, aiming to evaluate the efficacy of sildenafil on the ventilatory efficiency during exercise, in teenagers and adult patients (>15 years old) with an SV. Patients with a mean pulmonary arterial pressure >15 mmHg and a trans‐pulmonary gradient >5 mmHg, measured by cardiac catheterization, will be eligible. The primary outcome is the variation of the VE/VCO₂ slope, measured by a cardiopulmonary exercise test, between baseline and 6 months of treatment. A total of 50 patients are required to observe a decrease of 5 ± 5 points in the VE/VCO₂ slope, with a power of 90% and an alpha risk of 5%. The secondary outcomes are clinical outcomes, oxygen saturation, 6 min walk test, SV function, NT‐proBNP, peak VO₂, stroke volume, mean pulmonary arterial pressure, trans‐pulmonary gradient, SF36 quality of life score, safety, and acceptability.

Conclusions

The SV‐INHIBITION study aims to answer the question whether PDE5 inhibitors should be prescribed in patients with an SV. This trial has been built focusing on the three levels of research defined by the World Health Organization: disability (exercise tolerance), deficit (SV function), and handicap (quality of life).

Management of Pulmonary Arterial Hypertension in the Pediatric Patient

PURPOSE OF REVIEW

Pediatric pulmonary arterial hypertension (PAH) is associated with significant morbidity and mortality. Herein we review the diagnosis and classification for pediatric PAH and detail the current therapeutic options available for use in the pediatric PAH population.

RECENT FINDINGS

Classification and treatment of pediatric PAH is guided by adult criteria and treatment algorithms, yet the distribution of factors contributing to PAH in children differs significantly from that seen in adults. It is necessary to understand these differences in order to appropriately tailor therapy to the needs of the child or adolescent. An expanding array of targeted PAH drugs are now approved for use in adults, and many of these drugs are used "off-label" to treat children and adolescents with PAH. Use of these novel therapies has coincided with marked improvement in outcomes, suggesting significant benefit. However, because most of these drugs have not been studied in rigorous randomized, controlled trials in children, it is critical that physicians understand their mechanisms of action, potential benefits, and safety profiles. Pediatric PAH outcomes have improved substantially in the modern era, coinciding with the "off-label" use of targeted PAH drugs in children and adolescents. Ideally, care should be provided at centers with specialized expertise in the diagnosis and treatment of pediatric PAH by providers who understand the appropriate diagnostic algorithms, classification schemes, and treatment approaches.

Safety of enteral sildenafil in hemodynamically unstable children

BACKGROUND

Enteral sildenafil may be used in the intensive care unit for treatment of pulmonary arterial hypertension. We aimed to determine if initial enteral sildenafil dosing is safe in children receiving concurrent vasoactive infusions.

METHODS

We performed a single-centre retrospective chart review that included patients less than 2 years of age in paediatric and cardiovascular intensive care units at an academic medical centre from 1 January, 2010 to 30 November, 2016. Included patients received concomitant enteral sildenafil and a continuously infused vasoactive agent. Exclusion criteria consisted of mechanical circulatory support, any form of dialysis, or a suspicion of septic shock at the time of sildenafil initiation. We sought to identify patients who developed worsening hemodynamic instability after initiation of enteral sildenafil defined as one or more of the following observations within 24 hours of sildenafil initiation: sildenafil discontinuation, total fluid bolus receipt >10 ml/kg, increased vasoactive support, epinephrine intravenous push administration, and/or the initiation of mechanical circulatory support.

RESULTS

Worsening hemodynamic instability was identified in 35% of the 130-patient cohort. Patients younger than 4 months were at increased risk of further hemodynamic instability compared with older patients (56% versus 44%, p = 0.0003) despite receiving lower median doses (1.28 mg/kg/day versus 1.78 mg/kg/day, p = 0.01).

CONCLUSIONS

Critically ill children receiving vasoactive infusions may be at increased risk for further hemodynamic instability after initiation of enteral sildenafil, particularly in younger patients. This population may benefit from lower starting enteral sildenafil doses of 0.25 mg/kg/dose or less every 8 hours to avoid further hemodynamic compromise.

Routine Sildenafil Does Not Improve Clinical Outcomes After Fontan Operation

Fontan operation can be complicated by persistent chest tube output (CTO) leading to prolonged hospital length of stay (LOS). Postoperative sildenafil administration has been shown to improve clinical outcomes in selected patients after Fontan. We initiated a practice change utilizing intravenous (IV) sildenafil in early postoperative period in all patients undergoing Fontan operation with aim to decrease LOS and CTO. Nineteen patients (February 2014-May 2016) received 0.35 mg/kg sildenafil IV (three doses) followed by enteral, 1 mg/kg every eight hours until hospital discharge. Clinical outcomes were compared to 84 pre-protocol controls. Vital signs were recorded after second sildenafil dose. Demographics were similar between groups. Sildenafil group had longer median LOS [9 (7, 11) vs. 13 (8, 25) days, p = 0.016]. CTO days were longer [6 (5, 8) vs. 8 (6, 13) days, p = 0.011]. Sildenafil group had longer mechanical ventilation [6.9 (3.5, 11.1) vs. 4 (2, 7) h, p = 0.045] and longer oxygen therapy [99 (52, 225) vs. 14.5 (14, 56) h, p = 0.001]. There was a trend towards more albumin 5% resuscitation in first 24 h [17 (1, 30) vs. 21 (10, 40) ml/kg, p = 0.069]. There was no difference in inotrope score at 24 h, maximum lactate, or fluid balance. Readmission rates were similar. There was no mortality. IV sildenafil was well tolerated, and no doses were held. Routine early administration of sildenafil after Fontan operation is not associated with an improvement in any measured clinical outcome, including postoperative CTO, LOS, colloid administration, or duration of mechanical ventilation.

NOTCH1-Dependent Nitric Oxide Signaling Deficiency in Hypoplastic Left Heart Syndrome Revealed Through Patient-Specific Phenotypes Detected in Bioengineered Cardiogenesis

Hypoplastic left heart syndrome (HLHS) is a severe congenital heart defect (CHD) attributable to multifactorial molecular underpinnings. Multiple genetic loci have been implicated to increase the risk of disease, yet genotype-phenotype relationships remain poorly defined. Whole genome sequencing complemented by cardiac phenotype from five individuals in an HLHS-affected family enabled the identification of NOTCH1 as a prioritized candidate gene linked to CHD in three individuals with mutant allele burden significantly impairing Notch signaling in the HLHS-affected proband. To better understand a mechanistic basis through which NOTCH1 contributes to heart development, human induced pluripotent stem cells (hiPSCs) were created from the HLHS-affected parent-proband triad and differentiated into cardiovascular cell lineages for molecular characterization. HLHS-affected hiPSCs exhibited a deficiency in Notch signaling pathway components and a diminished capacity to generate hiPSC-cardiomyocytes. Optimization of conditions to procure HLHS-hiPSC-cardiomyocytes led to an approach that compensated for dysregulated nitric oxide (NO)-dependent Notch signaling in the earliest specification stages. Augmentation of HLHS-hiPSCs with small molecules stimulating NO signaling in the first 4 days of differentiation provided a cardiomyocyte yield equivalent to the parental hiPSCs. No discernable differences in calcium dynamics were observed between the bioengineered cardiomyocytes derived from the proband and the parents. We conclude that in vitro modeling with HLHS-hiPSCs bearing NOTCH1 mutations facilitated the discovery of a NO-dependent signaling component essential for cardiovascular cell lineage specification. Potentiation of NO signaling with small therapeutic molecules restored cardiogenesis in vitro and may identify a potential therapeutic target for patients affected by functionally compromised NOTCH1 variants. Stem Cells 2017;35:1106-1119.

Evaluation of the Tolerability of Intermittent Intravenous Sildenafil in Pediatric Patients With Pulmonary Hypertension

OBJECTIVES: The primary purpose of this study was to determine the tolerability of intermittent intravenous (IV) sildenafil for the treatment of pulmonary hypertension in pediatric patients. Secondary objectives were to evaluate parameters related to efficacy. METHODS: This was a retrospective chart review from January 2013 to August 2014 of pediatric patients under age 18 years treated with intermittent doses of IV sildenafil for pulmonary hypertension. Patients were excluded if they were over age 18 years or received sildenafil for other indications. Measures collected to assess tolerability include blood pressure and heart rate before and after the administration of IV sildenafil, as well as adverse events. RESULTS: Thirty-seven patients (21 females and 16 males) were identified meeting inclusion criteria, and 21 (56.8%) were on oral sildenafil prior to the initial IV dose. The mean decrease in blood pressure after the first dose of IV sildenafil was 7.16/2.74 mmHg. The decrease in systolic blood pressure was statistically significant. During the study period, 5 patients experienced medication related adverse events, primarily hypotension. Despite this, none of the patients had the medication discontinued due to these events. For secondary objectives, a statistically significant difference was not found between other clinical measures before and after intermittent IV sildenafil dosing. CONCLUSIONS: Sildenafil, when administered as intermittent IV doses, was tolerated by the majority of patients evaluated in this study. For pediatric patients with pulmonary hypertension in whom enteral or continuous IV sildenafil cannot be administered, intermittent IV sildenafil may be considered as an alternative administration option.

Pharmacokinetics of intravenous sildenafil in children with palliated single ventricle heart defects: effect of elevated hepatic pressures

Aims Sildenafil is frequently prescribed to children with single ventricle heart defects. These children have unique hepatic physiology with elevated hepatic pressures, which may alter drug pharmacokinetics. We sought to determine the impact of hepatic pressure on sildenafil pharmacokinetics in children with single ventricle heart defects.

METHODS

A population pharmacokinetic model was developed using data from 20 single ventricle children receiving single-dose intravenous sildenafil during cardiac catheterisation. Non-linear mixed effect modelling was used for model development, and covariate effects were evaluated based on estimated precision and clinical significance.

RESULTS

The analysis included a median (range) of 4 (2-5) pharmacokinetic samples per child. The final structural model was a two-compartment model for sildenafil with a one-compartment model for des-methyl-sildenafil (active metabolite), with assumed 100% sildenafil to des-methyl-sildenafil conversion. Sildenafil clearance was unaffected by hepatic pressure (clearance=0.62 L/hour/kg); however, clearance of des-methyl-sildenafil (1.94×(hepatic pressure/9)(-1.33) L/hour/kg) was predicted to decrease ~7-fold as hepatic pressure increased from 4 to 18 mmHg. Predicted drug exposure was increased by ~1.5-fold in subjects with hepatic pressures ⩾10 versus <10 mmHg (median area under the curve=533 versus 792 µg*h/L). Discussion Elevated hepatic pressure delays clearance of the sildenafil metabolite - des-methyl-sildenafil - and increases drug exposure. We speculate that this results from impaired biliary clearance. Hepatic pressure should be considered when prescribing sildenafil to children. These data demonstrate the importance of pharmacokinetic assessments in patients with unique cardiovascular physiology that may affect drug metabolism.

Sildenafil in pediatric pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a life-threatening disease of varied etiologies. Although PAH has no curative treatment, a greater understanding of pathophysiology, technological advances resulting in early diagnosis, and the availability of several newer drugs have improved the outlook for patients with PAH. Sildenafil is one of the therapeutic agents used extensively in the treatment of PAH in children, as an off-label drug. In 2012, the United States Food and Drug Administration (USFDA) issued a warning regarding the of use high-dose sildenafil in children with PAH. This has led to a peculiar situation where there is a paucity of approved therapies for the management of PAH in children and the use of the most extensively used drug being discouraged by the regulator. This article provides a review of the use of sildenafil in the treatment of PAH in children.

Effect of Tadalafil on Myocardial and Endothelial Function and Exercise Performance After Modified Fontan Operation

Better postoperative management of patients who have undergone single ventricle (SV) Fontan procedure could potentially reduce long-term complications and improve the quality of life for patients. The present study determined the effect of tadalafil on myocardial and endothelial function and exercise performance after modified Fontan operation. Patients who had undergone SV modified Fontan operation were enrolled in this clinical trial. The demographic characteristics of the patients were recorded. Before administration of tadalafil and after the trial, ventricular function (MPI, EF, FS, E/A, VTI), exercise performance, and endothelial function were evaluated for sonographic and biochemical markers (FMD, IMT, ICAM, VCAM, NO) using echocardiography, exercise testing, vascular ultrasonography, and biochemical measurements, respectively. A single dose of tadalafil of 1 mg/kg was administered daily for 6 weeks, and the functional class of the patients before and after tadalafil was determined. A total of 15 patients completed this clinical trial. Tadalafil was shown to have a significant effect on myocardial function, exercise performance, and improvement in NYHA functional class (p < 0.05) of study population. It had no significant effect on the biochemical variables and endothelial function except for IMT (p > 0.05), which decreased significantly after tadalafil administration (p < 0.05). The findings indicate that tadalafil is a safe, well-tolerated agent for the use after modified Fontan operation to improve myocardial function and exercise performance and possibly reduce long-term morbidity and mortality of patients. More conclusive results could be obtained from further study with a larger sample size and long-term follow-up.

Sildenafil exposure and hemodynamic effect after Fontan surgery

OBJECTIVE

Determine sildenafil exposure and hemodynamic effect in children after Fontan single-ventricle surgery.

DESIGN

Prospective dose-escalation trial.

SETTING

Single-center pediatric catheterization laboratory.

PATIENTS

Nine children post Fontan single-ventricle surgical palliation and undergoing elective cardiac catheterization: median (range) age and weight, 5.2 years (2.5-9.4 yr) and 16.3 kg (9.5-28.1 kg). Five children (55%) were boys, and six of nine (67%) had a systemic right ventricle.

INTERVENTIONS

Catheterization and echocardiography performed before and immediately after single-dose IV sildenafil (0.25, 0.35, or 0.45 mg/kg over 20 min).

MEASUREMENTS AND MAIN RESULTS

Peak sildenafil and desmethyl sildenafil concentration, change in hemodynamic variables measured by cardiac catheterization and echocardiography. Maximum sildenafil concentrations ranged from 124 to 646 ng/mL and were above the in vitro threshold needed for 77% phosphodiesterase type-5 inhibition in eight of nine children and 90% inhibition in seven of seven children with doses more than or equal to 0.35 mg/kg. Sildenafil improved stroke volume (+22%, p = 0.05) and cardiac output (+10%, p = 0.01) with no significant change in heart rate in eight of nine children. Sildenafil also lowered systemic (-16%, p = 0.01) and pulmonary vascular resistance index in all nine children (median baseline pulmonary vascular resistance index 2.4 [range, 1.3-3.7]; decreased to 1.9 [0.8-2.7] Wood Units × m; p = 0.01) with no dose-response effect. Pulmonary arterial pressures decreased (-10%, p = 0.02) and pulmonary blood flow increased (9%, p = 0.02). There was no change in myocardial performance index and no adverse events.

CONCLUSIONS

After Fontan surgery, sildenafil infusion acutely improves cardiopulmonary hemodynamics, increasing cardiac index. For the range of doses studied, exposure was within the acute safety range reported in adult subjects.