Caffeine dosing in premature neonates: impact of birth weight on a pharmacokinetic simulation study.

BACKGROUND: The optimal caffeine dosing in extremely premature neonates remains elusive. This study aimed to evaluate the impact of birth weight on caffeine pharmacokinetics and various dosing regimens. METHODS: In this pharmacokinetic simulation study, we generated the body weights (0-49 days of postnatal age [PNA]) of neonates <28 weeks gestational age with different birth weights (550, 750, and 1050 g). Their pharmacokinetic parameters were determined based on published pharmacokinetic models. Then, we simulated and compared the caffeine base concentration-time profiles of standard versus off-label caffeine citrate dose regimens. RESULTS: The half-life decreased and the weight-adjusted clearance increased more significantly in neonates with lower birth weights, resulting in lower caffeine plasma concentrations. The neonate with the lowest birth weight did not achieve a threshold trough concentration of 15 mg/L after receiving the standard dose (5 mg/kg/day), while the higher-birth-weights (≥750 g) had trough concentrations below the threshold around the second week of life. Higher caffeine doses (10 mg/kg/day) resulted in peak concentrations of <36 mg/L by 10-14 days of PNA while maintaining trough concentrations above 15 mg/L throughout the 49 days PNA. CONCLUSION: Higher-than-standard caffeine dosing may be needed for extremely premature neonates, especially for those with lower birth weights. IMPACT: Extremely premature neonates with a lower birth weight may require a higher weight-based caffeine dosing due to their higher weight-adjusted clearance and shorter half-lives. Not only do these extremely premature neonates have a higher risk of developing bronchopulmonary dysplasia due to their structurally underdeveloped lungs, but the low birth weight-related underdosing may further contribute to the reduced caffeine effectiveness. Higher-than-standard caffeine citrate dosing (e.g., 10 mg/kg/day maintenance dose) may be needed to further prevent bronchopulmonary dysplasia.

Ampicillin Dose for Early and Late-Onset Group B Streptococcal Disease in Neonates.

Ampicillin is frequently used in neonates for early- and late-onset group B streptococcal (GBS) disease. In 2019, the American Academy of Pediatrics (AAP) published guidelines for GBS which included updated dosing recommendations for ampicillin for bacteremia and provided specific dosing recommendations for meningitis. The dosing recommendations in the guidelines were based off the 2018 Report of the Committee on Infectious Diseases (i.e., Red Book), which differed from the 2015 Red Book. For bacteremia, no dosing changes were recommended for ampicillin dosing in neonates ≤ 7 days of postnatal age (PNA), but less frequent dosing intervals were recommended for neonates > 7 days PNA. For meningitis, increased dosing recommendations were provided in the update. However, the rationale and supporting evidence for these changes were not provided. A literature search was performed to review articles pertaining to the pharmacokinetics (PK), pharmacodynamics (PD) and safety of ampicillin in neonates. The ampicillin dosing recommendations in the AAP guidelines were mainly supported by a 2014 publication that evaluated the PK and PD of ampicillin in neonates with gestational age (GA) of 24 to 41 weeks and PNA of 0 to 25 days. The proposed dosing from this study for bacteremia is included in the 2018 Red Book and 2019 guidelines. For meningitis, no supporting evidence was identified for the dosing recommendations in the 2018 Red Book and 2019 guidelines. Only one study has evaluated ampicillin concentrations in cerebrospinal fluid, but proposed dosing from this study was much lower than that included in the guidelines. The high ampicillin doses for GBS meningitis should be used with caution, as high ampicillin concentrations have been associated with seizures and no studies have evaluated efficacy of this dosing strategy. The purpose of this review is to identify key pieces of literature regarding dosing recommendations and safety of ampicillin in neonates. KEY POINTS: · Recent guidelines provide dosing recommendations for ampicillin, but the supporting evidence is not included.. · Literature supporting evidence for ampicillin dosing for bacteremia is available, but not for dosing for meningitis.. · Recommended meningitis dose may result in supratherapeutic concentrations and increase seizure risk..

Conversion From Continuous Infusion Fentanyl to Continuous Infusion Hydromorphone in the Pediatric Intensive Care Unit.

BACKGROUND: Opioid rotations from fentanyl to hydromorphone may reduce opioid/sedative exposure in critically ill children. OBJECTIVE: The primary objective was to determine the conversion percentage from fentanyl to hydromorphone infusions using equianalgesic conversions (0.1 mg fentanyl = 1.5 mg hydromorphone). Secondary objectives included identification of the median time and hydromorphone rate at stabilization (defined as the first 24-hour period no hydromorphone rates changed, 80% of State Behavioral Scale [SBS] scores between 0 and -1, and <3 hydromorphone boluses administered). Additional outcomes included a comparison of opioid/sedative requirements on the day of conversion versus the three 24-hour periods prior to conversion. METHODS: This retrospective study included children <18 years old converted from fentanyl to hydromorphone infusions over 6.3 years. Linear mixed models were used to determine if the mean cumulative opioid/sedative dosing differed from the day of conversion versus three 24-hour periods prior to conversion. RESULTS: A total of 36 children were converted to hydromorphone. The median conversion percentage of hydromorphone was 86% of their fentanyl dose (interquartile range [IQR] = 67-100). The median hydromorphone rate at stabilization was 0.08 mg/kg/h (IQR = 0.05-0.1). Eight (22%) were stabilized on their initial hydromorphone rate; 8 (22%) never achieved stabilization. Patients had a significant decrease in opioid dosing on the day of conversion versus the 24-hour period prior to conversion but no changes in sedative dosing following conversion. CONCLUSION AND RELEVANCE: A median 14% fentanyl dose reduction was noted when transitioning to hydromorphone. Further exploration is needed to determine if opioid rotations with hydromorphone can reduce opioid/sedative exposure.

Prediction and Comparison of Fentanyl Infusion Pharmacokinetics in Obese and Nonobese Children.

OBJECTIVES: To compare fentanyl infusion pharmacokinetic variables in obese children and nonobese children. DESIGN: A pharmacokinetic simulation study. SETTING: We used a semi-physiologically based pharmacokinetic model to generate fentanyl pharmacokinetic variables. SUBJECTS: Simulations of pharmacokinetic variables were based on historical inpatient demographic data in less than 18-year-olds. INTERVENTIONS: Obese children were defined as children less than 2 years with weight-for-length greater than or equal to 97.7th percentile or body mass index-for-age greater than or equal to 95th percentile for greater than or equal to 2-17-year-olds. MEASUREMENTS AND MAIN RESULTS: Overall, 4,376 patients were included, with 807 (18.4%) classified as obese children. The majority (52.9%) were male, with a median age of 8.1 years (interquartile range, 4.3-13.0 yr). The differences in total clearance (CLS), volume of distribution at steady-state values, weight-normalized CLS, and weight-normalized volume of distribution at steady state were assessed in obese children and nonobese children. Multivariable analyses indicated that obesity was significantly associated with a higher CLS in obese children greater than 6-year-olds (p < 0.0375). However, there was an 11-30% decrease in weight-normalized CLS in obese children versus nonobese children in all age groups (p < 0.05). Both volume of distribution at steady state and weight-normalized volume of distribution at steady state increased significantly in obese children compared with nonobese children (p < 0.05). Fentanyl plasma concentration-time profiles of obese children and nonobese children pairs (ages 4, 9, and 15) receiving 1 µg/kg/hr using total body weight were also compared. Steady-state concentrations of the obese children using similar weight-based dosing increased by 25%, 77%, and 44% in comparison to nonobese children 4-, 9-, and 15-year-olds, respectively. Time to steady state and elimination half-lives were two- to four-fold longer in obese children. An additional simulation was conducted for 15-year-old obese children and nonobese children using a fixed dose of 50 µg/hr and it provided similar pharmacokinetic profiles. CONCLUSIONS: CLS may increase less than proportional to weight in obese children greater than 6-year-olds, while volume of distribution at steady state increases more than proportional to weight in all obese children compared with nonobese children. Weight-based dosing in obese children may cause an increase in steady-state concentration while prolonging the time to steady state. Exploring alternative dosing strategies for obese children is warranted.

Characterization of early versus late opioid iatrogenic withdrawal syndrome in critically ill children transitioning from fentanyl -infusions to methadone.

OBJECTIVE: Methadone is used to prevent opioid iatrogenic withdrawal syndrome (IWS) in children, but the optimal dose and overlap time with an opioid infusion have not been elucidated. The purpose was to compare clinical manifestations among patients who developed opioid IWS within 24 hours (early) versus ≥24 hours (late) of fentanyl discontinuation when enteral methadone was initiated. DESIGN: A retrospective, descriptive study. SETTING: Pediatric and cardiovascular intensive care units at a tertiary care health system. PARTICIPANTS: Sixty-seven children received fentanyl infusions for ≥3 days and initiated on methadone prior to fentanyl discontinuation. MAIN OUTCOME MEASURES: The primary objective was to compare clinical characteristics between those with early versus late opioid IWS. Opioid IWS was defined as a Withdrawal Assessment Tool-1 score ≥3 within 5 days of fentanyl discontinuation. Secondary objectives included a comparison of time to IWS, clinical characteristics, and risk factors among patients with and without IWS. RESULTS: Fifty children (74.6 percent) developed opioid IWS within a median time of 3.5 hours. No differences were noted for those with and without IWS. Thirty-seven patients (74.0 percent) with IWS developed early IWS. A higher percentage of males in the late versus early group developed IWS, 100 percent versus 51.4 percent, p = 0.002. The median overlap time with methadone and fentanyl was shorter in the early versus late IWS group without reaching statistical significance, 27.5 versus 64.0 hours, p = 0.127. CONCLUSIONS: The majority developed opioid IWS, with most developing early IWS, despite methadone initiation. Future studies should evaluate the optimal methadone dosing and overlap time to prevent opioid IWS.

Opioid tolerance and opioid-induced hyperalgesia: Is TrkB modulation a potential pharmacological solution?

Opioids are widely prescribed for moderate to severe pain in patients with acute illness, cancer pain, and chronic noncancer pain. However, long-term opioid use can cause opioid tolerance and opioid-induced hyperalgesia (OIH), contributing to the opioid misuse and addiction crisis. Strategies to mitigate opioid tolerance and OIH are needed to reduce opioid use and its sequelae. Currently, there are few effective pharmacological strategies that reduce opioid tolerance and OIH. The intrinsic tyrosine kinase receptor B (TrkB) ligand, brain-derived neurotrophic factor (BDNF), has been shown to modulate pain. The BDNF-TrkB signaling plays a role in initiating and sustaining elevated pain sensitivity; however, increasing evidence has shown that BDNF and 7,8-dihydroxyflavone (7,8-DHF), a potent blood-brain barrier-permeable ligand to TrkB, exert neuroprotective, anti-inflammatory, and antioxidant effects that may protect against opioid tolerance and OIH. As such, TrkB signaling may be an important therapeutic avenue in opioid tolerance and OIH. Here, we review 1) the mechanisms of pain, opioid analgesia, opioid tolerance, and OIH; 2) the role of BDNF-TrkB in pain modulation; and 3) the neuroprotective effects of 7,8-DHF and their implications for opioid tolerance and OIH.

Analysis of fentanyl pharmacokinetics, and its sedative effects and tolerance in critically ill children.

INTRODUCTION: Fentanyl pharmacokinetic and pharmacodynamic data are limited in mechanically ventilated children. This study aimed to assess the fentanyl pharmacokinetics (PK), the sedation outcome, and the development of tolerance in children receiving fentanyl continuous infusion. METHODS: This study included children admitted to the pediatric or cardiovascular intensive care unit between January 1 and October 31, 2016, who were >30 days to <18 years of age, receiving ventilatory support via endotracheal tube or tracheostomy, and receiving a fentanyl infusion. Population PK analysis was performed using a nonlinear mixed-effects model. The relationship between initial sedation outcome using State Behavioral Scale (SBS) and fentanyl exposure was assessed, and the observations consistent with tolerance were described. RESULTS: Seventeen children, with a median age of 0.83 years (range: 0.1-12) and weight of 8.7 kg (range: 3.4-52), were included. The fentanyl PK was adequately described by a weight-based allometry model with the power of 0.75 for clearance (CL=89.8 L/hr/70 kg) and distributional CL, and 1 for volumes of distribution. In infants <6.6 months, age was an additional factor for CL (31.4 L/h/70 kg) to account for age-related maturation. Seven of twelve nonparalyzed patients achieved goal sedation, defined as >80% of SBS scores ≤0 per 24 h, on the first day of fentanyl infusion with a median plasma concentration of 1.29 ng/ml (interquartile range: 0.78-2.05). Eight of the nine tolerant patients developed tolerance within a day of reaching goal sedation. CONCLUSION: Different weight-based fentanyl dosing rates may be required for infants and children of different ages to achieve similar plasma concentrations. Using SBS scores may guide the dosing titration of fentanyl that resulted in plasma concentrations within the therapeutic range of 1-3 ng/ml. For those who developed tolerance to fentanyl and/or a sedative, it was noted one day after goal sedation was achieved.

Evaluation of the Use of Caffeine Citrate Maintenance Doses >5 mg/kg/day in Preterm Neonates for Apnea of Prematurity.

OBJECTIVE: Caffeine citrate doses >5 mg/kg/day are frequently used for apnea of prematurity. The primary objective was identification of patients maintained on 5 mg/kg/day (Group 1). Secondary objectives included identification of patients requiring dose increases: 7.5 mg/kg every 24 hours (Group 2), 10 mg/kg every 24 hours (Group 3), and 5 mg/kg every 12 hours (Group 4); comparison of demographics and clinical characteristics; and identification of patients requiring dose adjustments owing to caffeine-associated tachycardia. METHODS: Retrospective study of neonates born between 23 to <31 weeks' gestation, receiving caffeine between January 1, 2015, and July 31, 2019. Patients receiving caffeine <1 week, initial maintenance dose >5 mg/kg/day, or with congenital abnormalities were excluded. Descriptive and inferential statistics were performed, with a p < 0.05. RESULTS: Overall, 281 patients were included, with 99 (35.2%) in Group 1; 56 (19.9%) in Group 2; 47 (16.7%) in Group 3; and 79 (28.1%) in Group 4. Significant differences in gestational age were noted, with Group 3 and 4 patients being more premature than Groups 1 and 2 (p < 0.001). Dose increases occurred at a median postnatal age and postmenstrual age of 13.0 days and 31.4 weeks in Group 2; 17.0 days and 30.3 weeks in Group 3; and 16.0 days and 30.1 weeks in Group 4. Significant differences were noted for development of tachycardia requiring dose adjustment, with Groups 3 and 4 having the highest percentage (p < 0.001). CONCLUSIONS: Two-thirds received caffeine citrate doses >5 mg/kg/day, with 44% receiving 10 mg/kg/day. Further exploration is necessary to determine the optimal PNA or PMA for dose adjustments.

Daptomycin Pharmacokinetics in Adolescents Undergoing Hemodialysis and Peritoneal Dialysis: A Case Series With Pharmacokinetic Modeling.

BACKGROUND: Children who undergo hemodialysis (HD) and peritoneal dialysis are at increased risk of infection. Daptomcyin is used to treat resistant infections; however, the pharmacokinetics of daptomycin in pediatric and adolescent dialysis patients remain unknown. METHODS: We report the safety and pharmacokinetics of a single intravenous 5 mg/kg dose of daptomycin for 6 individuals age 12 to 17 years old who underwent HD or continuous cycling peritoneal dialysis (CCPD). Daptomycin concentrations from all samples were determined by high-performance liquid chromatography. A non-compartmental analysis was performed to compare the pharmacokinetic parameters among HD and CCPD patients. A population pharmacokinetic model was developed to describe the concentration-time profiles of daptomycin in plasma, urine, and dialysis effluent. Monte Carlo simulations were performed to assess the pharmacodynamic outcomes. RESULTS: All subjects tolerated the single dose of daptomycin. During HD, significant drug removal was observed, compared with CCPD (26% vs 5% of total dose). A low daptomycin renal clearance (<12% of total clearance) with moderate variability (40.5%) was observed among subjects with residual renal function. An anuric and obese subject who received CCPD treatment appeared to have >80% higher daptomycin area under the plasma concentration-time curve than the other CCPD subjects. Dosing regimens that achieved predefined pharmacodynamic targets were reported. CONCLUSIONS: Daptomycin clearance was faster in 12- to 17-year-old patients receiving HD than CCPD. Administration of daptomycin immediately after HD reduces drug loss. The CCPD treatment, anuria, and obesity may increase the risk for drug accumulation. Our pharmacokinetic model can be further used to optimize dosing regimens of daptomycin in this population.

Model-Based Analysis of Cannabidiol Dose-Exposure Relationship and Bioavailability.

INTRODUCTION: There is a large variation in cannabidiol (CBD) pharmacokinetics and little information on its bioavailability. This study aims to establish the CBD dose-exposure relationship and to evaluate the effects of dosage forms, food, and doses on CBD absorption. METHODS: Single-dose (range: 5-6000 mg) CBD plasma concentration-time profiles administered as oral solution (OS), oral capsule (OC), or oromucosal spray/drop (OM) from healthy volunteers were extracted from 15 published clinical studies. A dose-exposure proportionality assessment was performed, and a population-based meta-analysis of CBD pharmacokinetics and systemic bioavailability was conducted with a nonlinear mixed-effects modeling. A three-compartment model with a Weibull or zero-order absorption model was used to describe CBD disposition and absorption kinetics. Dosage form, food, and dose were assessed for covariation. RESULTS: Oral solution CBD exposures increased less than proportionally with doses of 750 mg or greater, and bioavailability (6.5% at 3000 mg) decreased with increasing dose. The bioavailability of OC (5.6%) and fed-state OM (6.2%) were similar, whereas it was lower in fasted-state OM (0.9%). The Weibull absorption model best described OS, OC, and fed-state OM profiles. The slowest absorption rate was observed in OS, resulting in a time of maximum concentration of 4.75 hours, followed by fed-state OM (3.13 hrs) and OC (2.1 hrs). The absorption kinetics of fasted-state OM was best described by a zero-order absorption for the duration of 1.71 hours. CONCLUSION: The effects of doses, dosage forms, and feeding status on CBD pharmacokinetics were quantified and should be taken into consideration for dose optimization.

Pharmacokinetic considerations in pediatric pharmacotherapy.

PURPOSE: The changes in physiological functions as children grow and organ systems mature result in pharmacokinetic alterations throughout childhood. These alterations in children result in absorption, distribution, metabolism, and excretion of drugs that are different from those seen in the typical adult diseased population. SUMMARY: Changes in gastrointestinal motility and gastric pH in neonates and infants affect the absorption rate and bioavailability of drugs. Skin absorption rate and extent can be altered by different skin structures and perfusion in young children. Intramuscular and rectal absorption become less predictable in children due to erratic absorption site perfusion and other factors. Children's body compositions also differ greatly from that in adults. Water-soluble drugs distribute more extensively in newborns due to larger water content than in older children and adults. Drug elimination and excretion are also affected in pediatric population due to differences in liver and renal function. Immature enzyme development and renal function result in reduced clearance of drugs in young children. There are limited pharmacokinetic data available for many drugs used in children. CONCLUSION: Considering the changes in pharmacokinetics in children can help pharmacists optimize the dosing and monitoring of drugs and do the best they can to help this vulnerable population.

Prescribing Patterns of Continuous Infusions in Nonobese versus Obese Children Admitted to the Pediatric Intensive Care Unit.

This retrospective study compared the continuous infusions prescribed for obese and nonobese children. Ninety-five (13.2%) received an infusion. A greater percentage of obese ( n = 42/168) versus nonobese (53/552) children received infusions, p < 0.01. No difference was noted in the median number of infusions between the obese and nonobese groups, 2 versus 2, p = 0.975. The top 20 prescribed infusions included ten (50%) for sedation/analgesia or neuromuscular blockade and six (30%) for hemodynamic support. A literature search was performed for these 20 agents to determine pharmacokinetics, pharmacodynamics, and dosing in obese children and revealed six studies evaluating fentanyl ( n = 2), midazolam ( n = 1), and propofol ( n = 3).