Population Pharmacokinetics of Intravenous Paracetamol (Acetaminophen) in Preterm and Term Neonates: Model Development and External Evaluation

Intermittent intravenous paracetamol versus continuous morphine in infants undergoing cardiothoracic surgery: a multi-center randomized controlled trial

BACKGROUND

To determine whether intermittent intravenous (IV) paracetamol as primary analgesic would significantly reduce morphine consumption in children aged 0-3 years after cardiac surgery with cardiopulmonary bypass.

METHODS

Multi-center, randomized, double-blinded, controlled trial in four level-3 Pediatric Intensive Care Units (PICU) in the Netherlands and Belgium. Inclusion period; March 2016-July 2020. Children aged 0-3 years, undergoing cardiac surgery with cardiopulmonary bypass were eligible. Patients were randomized to continuous morphine or intermittent IV paracetamol as primary analgesic after a loading dose of 100 mcg/kg morphine was administered at the end of surgery. Rescue morphine was given if numeric rating scale (NRS) pain scores exceeded predetermined cutoff values. Primary outcome was median weight-adjusted cumulative morphine dose in mcg/kg in the first 48 h postoperative. For the comparison of the primary outcome between groups, the nonparametric Van Elteren test with stratification by center was used. For comparison of the proportion of patients with one or more NRS pain scores of 4 and higher between the two groups, a non-inferiority analysis was performed using a non-inferiority margin of 20%.

RESULTS

In total, 828 were screened and finally 208 patients were included; parents of 315 patients did not give consent and 305 were excluded for various reasons. Fourteen of the enrolled 208 children were withdrawn from the study before start of study medication leaving 194 patients for final analysis. One hundred and two patients received intermittent IV paracetamol, 106 received continuous morphine. The median weight-adjusted cumulative morphine consumption in the first 48 h postoperative in the IV paracetamol group was 5 times lower (79%) than that in the morphine group (median, 145.0 (IQR, 115.0-432.5) mcg/kg vs 692.6 (IQR, 532.7-856.1) mcg/kg; P < 0.001). The rescue morphine consumption was similar between the groups (p = 0.38). Non-inferiority of IV paracetamol administration in terms of NRS pain scores was proven; difference in proportion - 3.1% (95% CI - 16.6-10.3%).

CONCLUSIONS

In children aged 0-3 years undergoing cardiac surgery, use of intermittent IV paracetamol reduces the median weight-adjusted cumulative morphine consumption in the first 48 h after surgery by 79% with equal pain relief showing equipoise for IV paracetamol as primary analgesic. Trial Registration Clinicaltrials.gov, Identifier: NCT05853263; EudraCT Number: 2015-001835-20.

Prophylactic Intravenous Acetaminophen in Extremely Premature Infants: Minimum Effective Dose Research by Bayesian Approach

BACKGROUND

Patent ductus arteriosus (PDA) in preterm infants is associated with increased morbidities and mortality. Prophylactic treatment with cyclooxygenase inhibitors, as indomethacin or ibuprofen, failed to demonstrate significant clinical benefits. Acetaminophen may represent an alternative treatment option.

OBJECTIVE

This study evaluated the minimum effective dose of prophylactic acetaminophen to close the ductus and assessed the safety and tolerability profile in extremely preterm infants at 23-26 weeks of gestation.

METHODS

A dose finding trial with Bayesian continual reassessment method was performed in a multicenter study with premature infants hospitalized in neonatal intensive care unit. Infants of 23-26 weeks of gestation and post-natal age ≤ 12 h were enrolled. Four intravenous acetaminophen dose levels were predefined. The primary outcome was the ductus arteriosus closing at two consecutive echocardiographies or at day 7. The main secondary objectives included the safety of acetaminophen on hemodynamics and biological hepatic function.

RESULTS

A total of 29 patients were analyzed sequentially for the primary analysis with 20 infants assigned to the first dose level followed by 9 infants to the second dose level. No further dose level increase was necessary. The posterior probabilities of success, estimated from the Bayesian logistic model, were 46.1% [95% probability interval (PI), 24.9-63.9] and 67.6% (95% PI, 51.5-77.9) for dose level 1 and 2, respectively. A closing or closed pattern was observed among 19 patients at the end of treatment [65.5% (95% confidence interval (CI), 45.7-82.0)]. No change in alanine aminotransferase values was observed during treatment. A significant decrease in aspartate aminotransferase values was observed with postnatal age. No change in systolic and diastolic blood pressures was observed during treatment.

CONCLUSIONS

Minimum effective dose to close the ductus was 25 mg/kg loading dose then 10 mg/kg/6 h for 5 days in extremely preterm infants. Acetaminophen was well tolerated in this study following these doses.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04459117.

The Use of Population Pharmacokinetics to Extrapolate Food Effects from Human Adults and Beagle Dogs to the Pediatric Population Illustrated with Paracetamol as a Test Case

To date, food-drug interactions in the pediatric population remain understudied. The current food effect studies are mostly performed in adults and do not mimic the real-life situation in the pediatric population. Since the potential benefits of food effect studies performed in pediatrics should be counterbalanced with the burden that these studies pose to the patients, alternative research strategies should be evaluated. The present study aimed to evaluate whether population pharmacokinetics (popPK) using data in beagle dogs and human adults could reliably assess food effects relevant for the pediatric population. PopPK was utilized to understand the performance of paracetamol under different dosing conditions (when the participants were fasted, with a reference meal, and with infant formula) in human adults (n = 8) and beagle dogs (n = 6) by constructing models to derive the pharmacokinetic parameters and to evaluate the food effects in both species. A two-compartment model with a single input function for the absorption phase best described the profiles of paracetamol in the beagle dogs. In the human adults, a one-compartment model with a dual input function for the absorption phase best described the data. The simulated profiles for the different dosing conditions demonstrated that both the human adults' and beagle dogs' simulations were able to acceptably describe the plasma concentration-time profiles of paracetamol observed in a representative pediatric population, which opens up perspectives on pediatric-relevant food effect predictions. However, the obtained results should be carefully interpreted, since an accurate validation of these findings was not possible due to the scarcity of the literature on observed pediatric data.

Predicting Volume of Distribution in Neonates: Performance of Physiologically Based Pharmacokinetic Modelling

The volume of distribution at steady state (Vss) in neonates is still often estimated through isometric scaling from adult values, disregarding developmental changes beyond body weight. This study aimed to compare the accuracy of two physiologically based pharmacokinetic (PBPK) Vss prediction methods in neonates (Poulin & Theil with Berezhkovskiy correction (P&T+) and Rodgers & Rowland (R&R)) with isometrical scaling. PBPK models were developed for 24 drugs using in-vitro and in-silico data. Simulations were done in Simcyp (V22) using predefined populations. Clinical data from 86 studies in neonates (including preterms) were used for comparison, and accuracy was assessed using (absolute) average fold errors ((A)AFEs). Isometric scaling resulted in underestimated Vss values in neonates (AFE: 0.61), and both PBPK methods reduced the magnitude of underprediction (AFE: 0.82-0.83). The P&T+ method demonstrated superior overall accuracy compared to isometric scaling (AAFE of 1.68 and 1.77, respectively), while the R&R method exhibited lower overall accuracy (AAFE: 2.03). Drug characteristics (LogP and ionization type) and inclusion of preterm neonates did not significantly impact the magnitude of error associated with isometric scaling or PBPK modeling. These results highlight both the limitations and the applicability of PBPK methods for the prediction of Vss in the absence of clinical data.

Maturation of Paracetamol Elimination Routes in Preterm Neonates Born Below 32 Weeks of Gestation

PURPOSE

Despite being off-label, intravenous paracetamol (PCM) is increasingly used to control mild-to-moderate pain in preterm neonates. Here we aim to quantify the maturation of paracetamol elimination pathways in preterm neonates born below 32 weeks of gestation.

METHODS

Datasets after single dose (rich data) or multiple doses (sparse data) of intravenous PCM dose (median (range)) 9 (3-25) mg/kg were pooled, containing 534 plasma and 44 urine samples of PCM and metabolites (PCM-glucuronide, PCM-sulfate, PCM-cysteine, and PCM-mercapturate) from 143 preterm neonates (gestational age 27.7 (24.0-31.9) weeks, birthweight 985 (462-1,925) g, postnatal age (PNA) 5 (0-30) days, current weight 1,012 (462-1,959) g. Population pharmacokinetic analysis was performed using NONMEM® 7.4.

RESULTS

For a typical preterm neonate (birthweight 985 g; PNA 5 days), PCM clearance was 0.137 L/h, with glucuronidation, sulfation, oxidation and unchanged renal clearance accounting for 5.3%, 73.7%, 16.3% and 4.6%, respectively. Maturational changes in total PCM clearance and its elimination pathways were best described by birthweight and PNA. Between 500-1,500 g birthweight, total PCM clearance increases by 169%, with glucuronidation, sulfation and oxidation clearance increasing by 347%, 164% and 164%. From 1-30 days PNA for 985 g birthweight neonate, total PCM clearance increases by 167%, with clearance via glucuronidation and oxidation increasing by 551%, and sulfation by 69%.

CONCLUSION

Birthweight and PNA are the most important predictors for maturational changes in paracetamol clearance and its glucuronidation, sulfation and oxidation. As a result, dosing based on bodyweight alone will not lead to consistent paracetamol concentrations among preterm neonates.

Pharmacokinetics of acetaminophen after a single Oral administration of 20 or 40 mg/kg to 7-9 Day-old foals

Background

Acetaminophen is utilized in human infants for pain management and fever. Neonatal foals might benefit from administration of acetaminophen but effective and safe dosage regimens for neonatal foals remains to be determined.

Objective

The objective was to determine the plasma pharmacokinetics of acetaminophen following oral administration of a single dose of 20 mg/kg or 40 mg/kg to neonatal foals. A secondary objective was to evaluate any changes in hematology and biochemistry profiles.

Study design

Randomized study.

Methods

Eight clinically healthy 7-9-day old Quarter Horse foals (3 colts and 5 fillies) received a single oral dose of acetaminophen either 20 (n = 4) or 40 (n = 4) mg/kg. Hematology and biochemistry profiles were evaluated before and 7 days after drug administration. Blood samples were collected before and 8 times after acetaminophen administration for 48 h to quantify plasma acetaminophen concentrations. Plasma pharmacokinetic parameters were estimated using non- compartmental analysis.

Results

The median peak plasma concentrations (and range) occurred at 1.5 (0.5-2) hours, and 1.0 (1-2) hours for the 20 and 40 mg/kg doses. The maximum plasma concentration (and range) was 12 (7.9-17.4) μg/mL for the 20 mg/kg dose and 14 (11-18) μg/mL for 40 mg/kg dose. The median AUC_0-∞ ranged from 46 to 100 and 79 to 160 h*-μg/mL for the 20 and 40 mg/kg dose, respectively. Hematology and biochemistry profiles remained within normal limits.

Conclusion

Plasma disposition of acetaminophen after oral administration of 20 and 40 mg/kg to neonates is comparable to adult horses. However, safety and the optimal dosage regimen of acetaminophen for treating pain and or pyrexia in neonates in this age group remains to be determined.

Dexmedetomidine: An Alternative to Pain Treatment in Neonatology

Infants might be exposed to pain during their admissions in the neonatal intensive care unit [NICU], both from their underlying conditions and several invasive procedures required during their stay. Considering the particularities of this population, recognition and adequate management of pain continues to be a challenge for neonatologists and investigators. Diverse therapies are available for treatment, including non-pharmacological pain management measures and pharmacological agents (sucrose, opioids, midazolam, acetaminophen, topical agents…) and research continues. In recent years one of the most promising drugs for analgesia has been dexmedetomidine, an alpha-2 adrenergic receptor agonist. It has shown a promising efficacy and safety profile as it produces anxiolysis, sedation and analgesia without respiratory depression. Moreover, studies have shown a neuroprotective role in animal models which could be beneficial to neonatal population, especially in preterm newborns. Side effects of this therapy are mainly cardiovascular, but in most studies published, those were not severe and did not require specific therapeutic measures for their resolution. The main objective of this article is to summarize the existing literature on neonatal pain management strategies available and review the efficacy of dexmedetomidine as a new therapy with increasing use in the NICU.

Racing against time: leveraging preclinical models to understand pulmonary susceptibility to perinatal acetaminophen exposures

Over the past decade, clinicians have increasingly prescribed acetaminophen (APAP) for patients in the neonatal intensive care unit (NICU). Acetaminophen has been shown to reduce postoperative opiate burden, and may provide similar efficacy for closure of the patent ductus arteriosus (PDA) as nonsteroidal anti-inflammatory drugs (NSAIDs). Despite these potential benefits, APAP exposures have spread to increasingly less mature infants, a highly vulnerable population for whom robust pharmacokinetic and pharmacodynamic data for APAP are lacking. Concerningly, preclinical studies suggest that perinatal APAP exposures may result in unanticipated adverse effects that are unique to the developing lung. In this review, we discuss the clinical observations linking APAP exposures to adverse respiratory outcomes and the preclinical data demonstrating a developmental susceptibility to APAP-induced lung injury. We show how clinical observations linking perinatal APAP exposures to pulmonary injury have been taken to the bench to produce important insights into the potential mechanisms underlying these findings. We argue that the available data support a more cautious approach to APAP use in the NICU until large randomized controlled trials provide appropriate safety and efficacy data.

Population pharmacokinetic-pharmacodynamic modeling of acetaminophen in preterm neonates with hemodynamically significant patent ductus arteriosus

BACKGROUND

Pharmacokinetics (PK) of intravenous acetaminophen has not been assessed in preterm neonates with hemodynamically significant patent ductus arteriosus (PDA). Moreover, there is a lack of data evaluating the association between PK and pharmacodynamics (PD) of acetaminophen in hemodynamically significant PDA. Hence, we performed a population PK-PD modeling of acetaminophen in preterm neonates with hemodynamically significant PDA.

METHODS

A prospective, observational study was carried out in preterm neonates with hemodynamically significant PDA receiving intravenous acetaminophen (15 mg/kg six hourly) for maximum of nine days. The diameter of the ductus arteriosus was measured using General Electric Vivid 7® (echocardiography) and was the PD measure. The PK-PD modeling was performed using Monolix 2019R2. We performed Monte Carlo (MC) simulations to determine the probability of ductus arteriosus closure from first to the ninth day of acetaminophen treatment.

RESULTS

Fifty-five neonates were recruited. A one-compartment model with first-order elimination described well the PK of acetaminophen. Clearance (CL) and volume of distribution (Vd) for typical neonate weighing 0.98 kg was 0.0452 L/h and 1.18 L, respectively. A combination of an Imax model with effect compartment and an exponential disease progression model described well the PD of acetaminophen. The average baseline diameter of the ductus arteriosus (E0) was 2.53 mm while IC₅₀ was 0.477 µg/mL. The disease progression rate constant (Kprog) and effect compartment transfer rate constant (ke0) were 0.00425 h^-1 and 0.000103 h^-1, respectively. MC simulations of the current dosing regimen revealed a probability of 73.7% ductus arteriosus closure compared to 83.8% with 20 mg/kg six hourly dose.

CONCLUSION

The PK-PD model developed can be used for dosing acetaminophen in premature neonates with hemodynamically significant PDA. Intravenous dose of 20 mg/kg intravenously every six hours is likely to provide a better therapeutic effect than the existing dosing regimen.

Pharmacokinetics of Intravenous Paracetamol (Acetaminophen) and Ductus Arteriosus Closure After Premature Birth

In preterm infants, a high risk of hemodynamically significant patent ductus arteriosus (PDA) exists and its persistence is associated with an increased risk of severe morbidity. Current pharmacological options include ibuprofen or indomethacin. However, treatment by indomethacin or ibuprofen of a large PDA was shown to reduce early pulmonary hemorrhage and later medical treatment but had no effect on neonatal death or morbidity. Early prophylactic treatment of ductus arteriosus by paracetamol seems to be an attractive opportunity to reduce life-threatening morbidity. However, there are currently no data regarding the pharmacokinetics (PK) and pharmacodynamics of paracetamol in preterm neonates in this potential new indication. In this study, we aimed to develop a population PK model for paracetamol and investigate the relationship between paracetamol exposure levels and time to contraction of the ductus. Data were modeled using Monolix software. A one-compartment model adequately described the paracetamol concentration-time course. A Weibull model adequately described the time to contraction of the ductus. Our results suggest that the dosage used in this study (i.e., first day 42.5 mg/kg, then 30 mg/kg/day) allows for reaching the maximum inhibition response from paracetamol regarding the time to close the ductus. However, this study pointed out a lower effect of paracetamol on extremely preterm neonates (below 27 weeks). Therefore, a dose-finding study focusing specifically on extremely preterm neonates with treatment efficacy and toxicity is strongly needed.

Acetaminophen Therapy for Persistent Patent Ductus Arteriosus

Persistence of a left-to-right shunt caused by a patent ductus arteriosus (PDA) leads to significant sequelae in extremely premature infants as a result of pulmonary overcirculation and systemic steal. Although timing and duration of treatment for a persistent clinically significant PDA differ among institutions, standard pharmacologic interventions are the nonsteroidal anti-inflammatory drugs indomethacin and ibuprofen. Acetaminophen has emerged as an alternative to indomethacin and ibuprofen with less significant adverse effects, but there is no consensus regarding its use. This review summarizes the most recent evidence for the use of acetaminophen in PDA treatment.

Does high dose intravenous acetaminophen affect liver function for PDA closure in premature neonate?

Objectives

The aim of this study was to collect consistent data on the efficacy and safety and evaluation hepatotoxicity of intravenous acetaminophen for the treatment of PDA in preterm infants.

Methods

This is an observational longitudinal prospective study on 46 preterm infants with PDA who treated with high dose of acetaminophen and evaluated with echocardiography and serum liver enzymes at Hafez and Zeinabiyeh hospitals from January 2016 to December 2019.

Result

Forty-six preterm infants with PDA treated with intravenous acetaminophen. Rate of closure of PDA was 82.6. There was no significant difference after treatment regarding AST, ALT, Albumin, total and direct bilirubin (P value > 0.05) and no adverse side effects were observed in association with intravenous acetaminophen.

Conclusion

High dose of acetaminophen is not more effective than that with standard doses although without hepatotoxic side effect for PDA closure.

Paracetamol for patent ductus arteriosus in preterm infants: a UK national survey

Introduction: Evidence is emerging that paracetamol is a safe and effective alternative therapy for haemodynamically significant patent ductus arteriosus (hsPDA). Although there is no consensus opinion on its routine use for PDA in preterm infants, paracetamol is being used increasingly in many centres to treat hsPDA.Objective: We conducted a national survey to review the current practice in the UK and the prevalence of paracetamol use for hsPDA closure in preterm infants.Method: A web-based and telephone survey on the use of paracetamol for hsPDA closure in preterm infants was conducted. All neonatal intensive care and local neonatal units across the UK were contacted between May and August 2018.Results: 98% (143/146) neonatal units responded. The first-line medication for hsPDA closure was ibuprofen in 92% (131/143) units. 33% (47/143) of units used paracetamol; three units used it as first-line. The dose and duration of paracetamol varied greatly among the units with a dose of 15 mg/kg 6 hourly in 62% (29/47) units and a duration of 3 and 5 days in 33% (14/42) and 31% (13/42) of units, respectively. 44% (19/43) of units did routine blood investigations using paracetamol for monitoring patients on treatment and 21% (9/43) took paracetamol level in addition to other tests.Conclusion: 33% of the neonatal units across the UK offered paracetamol to treat hsPDA in preterm infants. Currently, there is a variation in practice regarding the dose, duration of paracetamol and monitoring of infants during its use for hsPDA closure. One strategy would be to develop national guidance once strong evidence is established to support its routine use for hsPDA in preterm infants.

Narcotic-Sparing Approaches and the Shift Toward Paracetamol in Neonatal Intensive Care

Effective analgesia in neonates is relevant not only because of ethical aspects or empathy, but it is a crucial and integral part of medical and nursing care. However, there is also emerging evidence - although mainly in animal models - on the relation between the exposure to narcotics and impaired neurodevelopmental outcome, resulting in a CATCH-22 scenario. Consequently, a balanced approach is needed with the overarching intention to attain adequate pain management with minimal side effects. Despite the available evidence-based guidance on narcotics in ventilated neonates, observations on drug utilization still suggest an overall increase in exposure with extensive variability between units. This increased exposure over time and the extensive variability is concerning given the limited evidence of benefits and potential harm.Implementation strategies are effective to reduce exposure to narcotics but result in increased paracetamol exposure. We therefore summarized the evidence on paracetamol use in procedural pain management, in minor to moderate as well as major pain syndromes in neonates. While there are sufficient data on short-term safety, there are still concerns on long-term side effects. These concerns relate to neurobehavioral outcome, atopy or fertility, and are at present mainly driven by epidemiological perinatal observations, together with postulated mechanisms.We conclude that future clinical research objectives should still focus on the need to develop better assessment tools to quantify pain and on the need for high-quality data on long-term outcome of therapeutic interventions - also for paracetamol - and exploration of the mechanisms involved.

A Critical Review on the Relevance of Paracetamol for Procedural Pain Management in Neonates

Effective and safe pain relief in neonates matters. This is not only because of ethical constraints or human empathy, but even more because pain treatment is an important and crucial part of contemporary medical, paramedical, and nursing care to improve the outcome in neonatal intensive care graduates. Paracetamol (acetaminophen) is likely one of the pharmacological tools to attain this, with data on prescription practices suggesting that paracetamol is somehow the "rising star" in neonatal pain management. Besides very rare topical clinical scenarios like peripartal asphyxia and subsequent whole body hypothermia or the use of cardiorespiratory support devices, data on paracetamol pharmacokinetics and metabolism were reported throughout neonatal age or weight ranges, and we have summarized these data. In this review, we subsequently aimed to provide the reader with the currently available observations on the use of paracetamol as analgesic for different pain syndromes (major surgery, minor surgery or trauma, and procedural pain), with focus on the limitations of paracetamol when prescribed for neonatal procedural pain management. We hereby intentionally will not discuss other indications (patent ductus arteriosus and fever) for paracetamol administration in neonates. Based on the available evidence, paracetamol has opioid-sparing effects for major pain syndromes, is effective to treat minor to moderate pain syndromes, but fails for effective procedural pain management in neonates. This efficacy failure for procedural pain management should stimulate us to continue to search for more effective interventions, including non-pharmacological interventions and preventive strategies. Furthermore, there are also upcoming association type of epidemiological studies on the relation between exposure to analgesics-including paracetamol-and the negative short- or long-term outcome characteristics (neuro-behavioral, atopy, and fertility). Consequently and in addition to the search for effective alternatives to prevent or treat pain, studies on long-term outcome following paracetamol exposure are needed to inform all stakeholders on the full effect-side effect balance of the different strategies to treat pain.

Electronic Health Record-Embedded Decision Support Platform for Morphine Precision Dosing in Neonates

Morphine is the opioid most commonly used for neonatal pain management. In intravenous form, it is administered as continuous infusions and intermittent injections, mostly based on empirically established protocols. Inadequate pain control in neonates can cause long-term adverse consequences; however, providing appropriate individualized morphine dosing is particularly challenging due to the interplay of rapid natural physiological changes and multiple life-sustaining procedures in patients who cannot describe their symptoms. At most institutions, morphine dosing in neonates is largely carried out as an iterative process using a wide range of starting doses and then titrating to effect based on clinical response and side effects using pain scores and levels of sedation. Our background data show that neonates exhibit large variability in morphine clearance resulting in a wide range of exposures, which are poorly predicted by dose alone. Here, we describe the development and implementation of an electronic health record-integrated, model-informed decision support platform for the precision dosing of morphine in the management of neonatal pain. The platform supports pharmacokinetic model-informed dosing guidance and has functionality to incorporate real-time drug concentration information. The feedback is inserted directly into prescribers' workflows so that they can make data-informed decisions. The expected outcomes are better clinical efficacy and safety with fewer side effects in the neonatal population.

Analgesics and Sedatives in Critically Ill Newborns and Infants: The Impact on Long-Term Neurodevelopment

Inadequate pain and/or stress management in preterm- and term-born infants has been associated with increased morbidity and even mortality. However, exposure to analgosedatives during early infancy may also be one of the risk factors for subsequent neurodevelopmental impairment, at least in animal studies. Because infants admitted to neonatal or pediatric intensive care units may receive high amounts of these drugs for prolonged periods of time and the majority of these infants nowadays survive to discharge, this is of major concern. A balanced approach that incorporates the assessment and quantification of both wanted effects as well as unwanted side effects is therefore needed. In this article, the optimal dose determination of commonly used analgosedative drugs as well as their potential long-term effects on the developing human brain and neuropsychological functioning are reviewed.

Development and comparison of population pharmacokinetic models of vancomycin in neurosurgical patients based on two different renal function markers

WHAT IS KNOWN AND OBJECTIVES

Some previous studies have indicated that serum cystatin C (Cys C) is a better marker than serum creatinine (SCR) for assessing the glomerular filtering rate (GFR). However, in almost all population pharmacokinetic models of vancomycin, the GFR is usually estimated from SCR. Therefore, the aim of this study was to compare the GFR estimated from SCR (sGFR) with the GFR estimated from Cys C (cGFR) and investigate which one can describe the characteristics of vancomycin population pharmacokinetics better in Chinese neurosurgical adult patients.

METHODS

Patients from the Neurosurgery Department aged ≥18 years were enrolled retrospectively. Among these patients, the data from 222 patients were used to establish two population pharmacokinetic models based on sGFR and cGFR, separately. The data from another 95 patients were used for the external validation of these two models. Non-linear mixed-effect modelling (NONMEM) 7.4.3 was used for the population pharmacokinetic analysis.

RESULTS

We developed two one-compartment models with first-order absorption based on Cys C and SCR, separately. In the Cys C model, age, body weight and cGFR were significant covariates on the clearance rate (CL) of vancomycin (typical value, 6.4 L/hour). In the SCR model, age and sGFR were significant covariates on the CL (typical value, 6.46 L/hour). The external validation results showed that the predictive performance of the two models was similar.

WHAT IS NEW AND CONCLUSION

In this study, the predictive performance of two models was similar in neurosurgical patients. We did not find a significant improvement in the predictive performance of the model when GFR was estimated from Cys C.

Randomized Population Pharmacokinetic Analysis and Safety of Intravenous Acetaminophen for Acute Postoperative Pain in Neonates and Infants

Intravenous administration of acetaminophen is an alternative to the oral and rectal routes, which may be contraindicated in particular clinical settings. This randomized, placebo-controlled study of intravenous acetaminophen (Ofirmev, Mallinckrodt Pharmaceuticals, Bedminster, New Jersey) in neonate and infant patients with acute postoperative pain assessed pharmacokinetics (PK) and safety, in addition to efficacy and pharmacodynamics of repeated doses administered over 24 hours. Neonate and infant patients (<2 years of age) who were undergoing surgery or had experienced a traumatic injury and were expected to need pain management for at least 24 hours were enrolled. Subjects were randomly assigned to receive intravenous acetaminophen low dose, intravenous acetaminophen high dose, or placebo. A population PK model of intravenous acetaminophen was updated by combining 581 samples from the current study of 158 neonate and infant subjects with results from a previously developed model. The individual predicted-versus-observed concentrations plots showed that the structural PK model fit the blood and plasma acetaminophen concentration-versus-time profiles in the active and placebo groups. Terminal elimination half-life was prolonged in neonates and younger infants and in intermediate and older infants similar to values in adults. When compared with placebo, total rescue opioid consumption was similar and significantly fewer intravenous acetaminophen patients prematurely discontinued because of treatment-emergent adverse events (P < .01). For intravenous acetaminophen, neonates receiving 12.5 mg/kg every 6 hours had PK profiles similar to younger, intermediate, and older infants, adolescents, and adults weighing <50 kg receiving 15 mg/kg every 6 hours and adults ≥ 50 kg receiving 1000 mg every 6 hours.

Population Pharmacokinetic Modeling in the Presence of Missing Time-Dependent Covariates: Impact of Body Weight on Pharmacokinetics of Paracetamol in Neonates

Body weight is the primary covariate in pharmacokinetics of many drugs and dramatically changes during the first weeks of life of neonates. The objective of this study is to determine if missing body weights in preterm and term neonates affect estimates of model parameters and which methods can be used to improve performance of a population pharmacokinetic model of paracetamol. Data for our analysis were obtained from previously published studies on the pharmacokinetics of intravenous paracetamol in neonates. We adopted a population model of body weight change in neonates to implement three previously introduced methods of handling missing covariates based on data imputation, likelihood function modification, and full random effects modeling. All models were implemented in NONMEM 7.4, and population parameters were estimated using the FOCE method. Our major finding was that missing body weights minimally affect population estimates of pharmacokinetic parameters but do affect the covariate relationship parameters, particularly the one describing dependence of clearance on body weight. None of the tested methods changed estimates of between-subject variability nor impacted the predictive performance of the model. Our analysis shows that a modeling approach towards handling missing covariates allows borrowing information gathered in various studies as long as they target the same population. This approach is particularly useful for handling time-dependent missing covariates.

Acetaminophen Serum Concentrations in Infants Treated Intravenously for Patent Ductus Arteriosus

OBJECTIVE

Although acetaminophen has emerged as a therapeutic option for treating hemodynamically significant patent ductus arteriosus (PDA) in preterm infants, limited data exist on pharmacodynamics. The objective of this research is to report serum acetaminophen concentrations at steady state in infants treated with intravenous acetaminophen for PDA and to examine associations with clinical outcomes.

METHODS

This retrospective study evaluated all infants admitted during the study period who received intravenous acetaminophen for the treatment of PDA. Acetaminophen dosing was 15 mg/kg every 6 hours. A serum acetaminophen concentration was obtained 4 hours after the eighth dose. Associations between serum concentrations and efficacy, assessed by ductal constriction on echocardiogram, and safety, assessed by serum creatinine and hepatic transaminases, were explored using simple linear regression.

RESULTS

A total of 36 infants were included, with a median birth weight of 720 g (IQR 585-895 g) and a median gestational age of 25 weeks (IQR 24-26 weeks). The median acetaminophen concentration in the cohort was 12.3 mg/L (IQR 6.7-16.5 mg/L; range, 1.1-29.0 mg/L). Serum acetaminophen concentrations did not correlate with infant demographics, hepatic transaminases during treatment, or duct size at treatment completion. We observed ductal closure across a wide range of serum acetaminophen concentrations.

CONCLUSIONS

We did not identify an association between acetaminophen serum concentrations following intravenous therapy and ductal response or hepatic toxicity.

A pilot randomised blinded placebo-controlled trial of paracetamol for later treatment of a patent ductus arteriosus

OBJECTIVE

To explore the efficacy and risks of oral paracetamol in later (>2 weeks old) treatment of patent ductus arteriosus (PDA).

STUDY DESIGN

A multicentre double-blind placebo-controlled randomised pilot trial in three neonatal intensive care units in Australia. Infants born <33 weeks with haemodynamically significant PDA were treated with a 5-day course of oral paracetamol or placebo. Cardiac ultrasounds were used to document haemodynamic parameters. The primary outcome analysed was ductal closure by 48 h after treatment completion. Secondary outcomes included reduction in ductal diameter >25% and safety.

RESULTS

Fifty-five infants were enrolled, of whom 27 received paracetamol and 28 placebo. Eighty percent had received previous non-steroidal anti-inflammatory drug. Mean postnatal age was 25 days. Four of the 27 ducts treated with paracetamol closed vs. 0/28 treated with placebo (p = 0.05). An additional 13/27 given  paracetamol vs. 7/28 given placebo showed significant constriction (p = 0.008). No adverse effects were observed .

CONCLUSIONS

There was some evidence of increased closure with oral paracetamol at postnatal age >2 weeks; however, the overall efficacy was not high.

Simultaneous determination of acetaminophen and oxycodone in human plasma by LC-MS/MS and its application to a pharmacokinetic study

A simple and rapid liquid chromatography–tandem mass spectrometry (LC–MS/MS) method was developed and validated for simultaneous determination of acetaminophen and oxycodone in human plasma. Acetaminophen-d4 and oxycodone-d3 were used as internal standards. The challenge encountered in the method development that the high plasma concentration level of acetaminophen made the MS response saturated while the desired lower limit of quantification (LLOQ) for oxycodone was hard to reach was well solved. The analytes were extracted by protein precipitation using acetonitrile. The matrix effect of the analytes was avoided by chromatographic separation using a hydrophilic C₁₈ column coupled with gradient elution. Multiple reaction monitoring in positive ion mode was performed on tandem mass spectrometer employing electrospray ion source. The calibration curves were linear over the concentration ranges of 40.0–8000 ng/mL and 0.200–40.0 ng/mL for acetaminophen and oxycodone, respectively. This method, which could contribute to high throughput analysis and better clinical drug monitoring, was successfully applied to a pharmacokinetic study in healthy Chinese volunteers.

Assessing the impact of in-utero exposures: potential effects of paracetamol on male reproductive development

Human male reproductive disorders (cryptorchidism, hypospadias, testicular cancer and low sperm counts) are common and some may be increasing in incidence worldwide. These associated disorders can arise from subnormal testosterone production during fetal life. This has resulted in a focus on in-utero environmental influences that may result in reproductive effects on the offspring in later life. Over recent years, there has been a dramatic increase in the scientific literature describing associations between in-utero environmental exposures (eg, industrial chemicals and pharmaceuticals) and subsequent reproductive outcomes in male offspring. This includes studies investigating a potential role for in-utero analgesic exposure(s) on the fetal testis; however, providing definitive evidence of such effects presents numerous challenges. In this review, we describe an approach to assessing the potential clinical relevance of in-utero (and postnatal) environmental exposures on subsequent male reproductive function using exposure to the analgesic paracetamol as an example.

Non-steroidal Anti-inflammatory Drugs in Newborns and Infants

Nonsteroidal antiinflammatory drugs (NSAIDs) and acetaminophen are used in young infants and newborns for pain and fever control, patent ductus closure, prevention of intraventricular hemorrhage, and potentially for prevention of retinopathy of prematurity. These drugs inhibit cyclooxygenase 1 (COX-1), COX-2, and peroxidases, thus, blocking prostaglandin (PG) synthesis. PGs are eicosanoids that regulate several physiologic, pathologic, and cellular processes, including vasomotor tone, platelet aggregation, sensitization of neurons to pain, and many molecular events critical to physiologic homeostasis. NSAIDs inhibit caspases and cell death. Increasing knowledge of these molecular entities may allow targeted drug development to prevent or minimize neonatal morbidities.

Quantification of Acetaminophen and Its Metabolites in Plasma Using UPLC-MS: Doors Open to Therapeutic Drug Monitoring in Special Patient Populations

BACKGROUND

Acetaminophen (APAP, paracetamol) is the most commonly used drug for pain and fever in both the United States and Europe and is considered safe when used at registered dosages. Nevertheless, differences between specific populations lead to remarkable changes in exposure to potentially toxic metabolites. Furthermore, extended knowledge is required on metabolite formation after intoxication, to optimize antidote treatment. Therefore, the authors aimed to develop and validate a quick and easy analytical method for simultaneous quantification of APAP, APAP-glucuronide, APAP-sulfate, APAP-cysteine, APAP-glutathione, APAP-mercapturate, and protein-derived APAP-cysteine in human plasma by ultraperformance liquid chromatography-electrospray ionization-tandem mass spectrometry.

METHODS

The internal standard was APAP-D4 for all analytes. Chromatographic separation was achieved with a reversed-phase Acquity ultraperformance liquid chromatography HSS T3 column with a runtime of only 4.5 minutes per injected sample. Gradient elution was performed with a mobile phase consisting of ammonium acetate, formic acid in Milli-Q ultrapure water or in methanol at flow rate of 0.4 mL/minute.

RESULTS

A plasma volume of only 10 μL was required to achieve both adequate accuracy and precision. Calibration curves of all 6 analytes were linear. All analytes were stable for at least 48 hours in the autosampler; the high quality control of APAP-glutathione was stable for 24 hours. The method was validated according to the U.S. Food and Drug Administration guidelines.

CONCLUSIONS

This method allows quantification of APAP and 6 metabolites, which serves purposes for research, as well as therapeutic drug monitoring. The advantage of this method is the combination of minimal injection volume, a short runtime, an easy sample preparation method, and the ability to quantify APAP and all 6 metabolites.

Perinatal and neonatal use of paracetamol for pain relief

Paracetamol (acetaminophen) is the most widely used drug to treat pain or fever in pregnant women or neonates, but its pharmacokinetics (PK) and pharmacodynamics (PD) warrant a focused analysis. During pregnancy, there is an important increase in paracetamol clearance. Consequently, it is reasonable to anticipate that the analgesic effect of paracetamol will decrease faster, whereas higher doses may result in even higher oxidative toxic metabolites. Therefore, most peripartal PD data relate to multimodal analgesia strategies. In neonates, weight/size is the most relevant covariate of paracetamol PK. This resulted in proposed dosing regimens containing higher doses than currently prescribed in the label for term neonates. Using adequate dosing, paracetamol is a poor procedural analgesic, is effective for mild-to-moderate pain, and has morphine-sparing effects. Short-term safety has been well documented, and there is active research investigating the potential association between paracetamol exposure and atopy, fertility, and neurobehavior.

Exposure to acetaminophen and all its metabolites upon 10, 15, and 20 mg/kg intravenous acetaminophen in very-preterm infants

BackgroundExposure to acetaminophen and its metabolites in very-preterm infants is partly unknown. We investigated the exposure to acetaminophen and its metabolites upon 10, 15, or 20 mg/kg intravenous acetaminophen in preterm infants.MethodsIn a randomized trial, 59 preterm infants (24-32 weeks' gestational age, postnatal age <1 week) received 10, 15, or 20 mg/kg acetaminophen intravenously. Plasma concentrations of acetaminophen and its metabolites (glucuronide, sulfate, cysteine, mercapturate, and glutathione) were determined in 293 blood samples. Area under the plasma concentration-time curves (AUC_0-500 min) was related to dose and gestational age.ResultsBetween 10 and 20 mg/kg dose, median AUCs of acetaminophen, glucuronide, sulfate, and cysteine increased significantly resulting in unchanged ratios of AUC of metabolite to acetaminophen. The AUC ratio of glucuronide to acetaminophen increased with gestational age, that of sulfate decreased, and the ratio of cysteine and mercapturate remained unchanged.ConclusionWe found a gestational-age-dependent increase in glucuronidation but no evidence for saturation of a specific pathway as there was a proportional increase in exposure of acetaminophen and all metabolites. Compared with adults, very low exposure to glucuronide but higher exposure to sulfate, cysteine, and mercapturate metabolites was found, of which the relevance is not yet known.

Neonatal Maturation of Paracetamol (Acetaminophen) Glucuronidation, Sulfation, and Oxidation Based on a Parent-Metabolite Population Pharmacokinetic Model

OBJECTIVES

This study aimed to model the population pharmacokinetics of intravenous paracetamol and its major metabolites in neonates and to identify influential patient characteristics, especially those affecting the formation clearance (CL_formation) of oxidative pathway metabolites.

METHODS

Neonates with a clinical indication for intravenous analgesia received five 15-mg/kg doses of paracetamol at 12-h intervals (<28 weeks' gestation) or seven 15-mg/kg doses at 8-h intervals (≥28 weeks' gestation). Plasma and urine were sampled throughout the 72-h study period. Concentration-time data for paracetamol, paracetamol-glucuronide, paracetamol-sulfate, and the combined oxidative pathway metabolites (paracetamol-cysteine and paracetamol-N-acetylcysteine) were simultaneously modeled in NONMEM 7.2.

RESULTS

The model incorporated 259 plasma and 350 urine samples from 35 neonates with a mean gestational age of 33.6 weeks (standard deviation 6.6). CL_formation for all metabolites increased with weight; CL_formation for glucuronidation and oxidation also increased with postnatal age. At the mean weight (2.3 kg) and postnatal age (7.5 days), CL_formation estimates (bootstrap 95% confidence interval; between-subject variability) were 0.049 L/h (0.038-0.062; 62 %) for glucuronidation, 0.21 L/h (0.17-0.24; 33 %) for sulfation, and 0.058 L/h (0.044-0.078; 72 %) for oxidation. Expression of individual oxidation CL_formation as a fraction of total individual paracetamol clearance showed that, on average, fractional oxidation CL_formation increased <15 % when plotted against weight or postnatal age.

CONCLUSIONS

The parent-metabolite model successfully characterized the pharmacokinetics of intravenous paracetamol and its metabolites in neonates. Maturational changes in the fraction of paracetamol undergoing oxidation were small relative to between-subject variability.

Paracetamol in Patent Ductus Arteriosus Treatment: Efficacious and Safe?

In preterm infants, failure or delay in spontaneous closure of Ductus Arteriosus (DA), resulting in the condition of Patent Ductus Arteriosus (PDA), represents a significant issue. A prolonged situation of PDA can be associated with several short- and long-term complications. Despite years of researches and clinical experience on PDA management, unresolved questions about the treatment and heterogeneity of clinical practices in different centers still remain, in particular regarding timing and modality of intervention. Nowadays, the most reasonable strategy seems to be reserving the treatment only to hemodynamically significant PDA. The first-line therapy is medical, and ibuprofen, related to several side effects especially in terms of nephrotoxicity, is the drug of choice. Administration of oral or intravenous paracetamol (acetaminophen) recently gained attention, appearing effective as traditional nonsteroidal anti-inflammatory drugs (NSAIDs) in PDA closure, with lower toxicity. The results of the studies analyzed in this review mostly support paracetamol efficacy in ductal closure, with inconstant low and transient elevation of liver enzymes as reported side effect. However, more studies are needed to confirm if this therapy shows a real safety profile and to evaluate its long-term outcomes, before considering paracetamol as first-choice drug in PDA treatment.

Pharmacokinetics, pharmacodynamics and pharmacogenetics associated with nonsteroidal anti-inflammatory drugs and opioids in pediatric cancer patients

INTRODUCTION

Advancing appropriate and adequate analgesic pharmacotherapy in pediatric patients with cancer is an area of clinical need. Few studies have been performed to evaluate the selection of an analgesic and appropriate dosing corresponding to analgesic effect among pediatric cancer patients. This review describes information related to pharmacokinetic, pharmacodynamic, and pharmacogenomic (when applicable) considerations for analgesics that are commonly used to manage pain experienced by pediatric patients with cancer. Areas covered: Analgesics commonly used to treat pediatric patients with malignancy patterned after the World Health Organization's 'analgesic ladder' for cancer pain management. Expert opinion: Addressing pain management safely and effectively in pediatric patients with cancer will require advances in both drug development, to increase the armament of analgesics available for children, and our pharmacologic understanding of those analgesics in current use. However, performing the necessary types of studies to develop new analgesics, or gain knowledge of existing therapy, within a population that is relatively small, diverse, and who experience pain originating from a variety of sources, is a tremendous challenge.

Paracetamol and morphine for infant and neonatal pain; still a long way to go?

INTRODUCTION

Pharmacologic pain management in newborns and infants is often based on limited scientific data. To close the knowledge gap, drug-related research in this population is increasingly supported by the authorities, but remains very challenging. This review summarizes the challenges of analgesic studies in newborns and infants on morphine and paracetamol (acetaminophen). Areas covered: Aspects such as the definition and multimodal character of pain are reflected to newborn infants. Specific problems addressed include defining pharmacodynamic endpoints, performing clinical trials in this population and assessing developmental changes in both pharmacokinetics and pharmacodynamics. Expert commentary: Neonatal and infant pain management research faces two major challenges: lack of clear biomarkers and very heterogeneous pharmacokinetics and pharmacodynamics of analgesics. There is a clear call for integral research addressing the multimodality of pain in this population and further developing population pharmacokinetic models towards physiology-based models.

Neonatal pain management: still in search for the Holy Grail

Inadequate pain management but also inappropriate use of analgesics in early infancy has negative effects on neurodevelopmental outcome. As a consequence, neonatal pain management is still in search for the Holy Grail. At best, effective pain management is based on prevention, assessment, and treatment followed by a re-assessment of the pain to determine if additional treatment is still necessary. Unfortunately, epidemiological observations suggest that neonates are undergoing painful procedures very frequently, unveiling the need for effective preventive, non-pharmacological strategies. In addition, assessment is still based on validated, multimodal, but subjective pain assessment tools. Finally, in neonatal intensive care units, there is a shift in clinical practices (e.g., shorter intubation and ventilation), and this necessitates the development and validation of new pharmacological treatment modalities. To illustrate this, a shift in the use of opioids to paracetamol has occurred and short-acting agents (remifentanil, propofol) are more commonly administered to neonates. In addition to these new modalities and as part of a more advanced approach of the developmental pharmacology of analgesics, pharmacogenetics also emerged as a tool for precision medicine in neonates. To assure further improvement of neonatal pain management the integration of pharmacogenetics with the usual covariates like weight, age and/or disease characteristics is needed.