Opioid Treatment for Neonatal Opioid Withdrawal Syndrome: Current Challenges and Future Approaches

Bayesian Population Pharmacokinetic Modeling of Ondansetron for Neonatal Opioid Withdrawal Syndrome

Ondansetron is an anti-emetic 5-HT3 receptor antagonist being investigated for treating neonatal opioid withdrawal syndrome (NOWS). Sparse PK data were analyzed from a multicenter, double-blind clinical trial with 98 mother/neonate dyads. Pregnant women with opioid use disorder were randomized to receive either placebo or ondansetron 8 mg intravenously within 4 h of delivery. Neonates born to mothers who were randomized to ondansetron received 0.07 mg/kg orally once every 24 h for up to five doses. Using current PK data, model parameters from a two-compartmental structural model from the literature (i.e., a priori model) were updated with the Metropolis-Hastings Markov-chain Monte Carlo estimation algorithm in NONMEM. The updated Bayesian model indicated a slower absorption rate (KA) but no differences in model parameters (CL, V, V2, Q) after including body weight and postmenstrual age. Sensitivity analyses on CL prior revealed statistical improvement favoring larger body weights, but not changes in postmenstrual age. However, further model development using larger body weights did not illustrate superior performance through visual inspection of diagnostic plots. Overall, a cumulative AUC of at least 1000 ng*h/mL appears to be the threshold for reductions in symptom severity. Exposure-response analyses suggest the total number of doses to be the primary driver for efficacy with respect to AUC, which reasonably aligns with the literature. Overall, it is suggested that at least three doses of the current oral ondansetron regimen are required to reduce symptom severity in neonates.

Recent Update on Pretreatment and Analysis Methods of Buprenorphine in Different Matrix

Buprenorphine is one of the most commonly used pain-killing drugs due to its lengthy duration of action and high potency. However, excessive usage of buprenorphine can be harmful to one's health and prolonged use might result in addiction. Additionally, an increasing number of cases have been documented involving the illegal use of buprenorphine. Therefore, a variety of effective and reliable methods for pretreatment and determination of buprenorphine and its main metabolite norbuprenorphine have been established. This review aims to update the current state of pretreatment and detection techniques for buprenorphine and norbuprenorphine from January 2010 to March 2022. Pretreatment methods include several traditional extraction methods, solid-phase extraction, QuECHERS, various micro-extraction techniques, etc. while analytical methods include LC-MS, LC coupled with other detectors, GC-MS, capillary electrophoresis, electrochemical sensors, etc. The pros and cons of various techniques were compared and summarized, and the prospects were provided.HIGHLIGHTSProgress in pretreatment and detection methods for buprenorphine is demonstrated.Pros and cons of different pretreatment and analysis methods are compared.New materials (such as nanomaterials and magnetic materials) used in buprenorphine pretreatment are summarized.Newly emerged environmental-friendly methods are discussed.

Neonatal Opioid Withdrawal Syndrome Treatment Guidelines and Birth Hospital Utilization

BACKGROUND AND OBJECTIVES

In November 2020, the American Academy of Pediatrics published guidelines for management of neonatal opioid withdrawal syndrome (NOWS), recommending nonpharmacologic treatment as the first-line approach, unless pharmacologic treatment is needed for severe NOWS. Using data from tertiary care pediatric hospitals, we examined the impact of the guidelines on use of pharmacotherapy, length of stay, and NICU admission for infants with NOWS.

METHODS

We extracted birth hospitalization data for newborns diagnosed with NOWS discharged from 2019 to 2022 from the Pediatric Health Information System. We compared hospital utilization and pharmacologic treatment pre- and postguidelines and used interrupted time series regression to examine trends over time.

RESULTS

We included N = 824 newborns (n = 434 pre, n = 390 post) with NOWS from 11 hospitals. The use of pharmacologic treatment was significantly lower in the postguidelines period (59.0% pre versus 50.3% post; P = .01). Median length of stay was similar pre and post (P = .55). NICU admission was significantly lower in the postguidelines period (78.6% pre versus 46.7% post; P < .001), with an immediate decrease (β = -23.0%; P < .001) and a decrease over time in the postguidelines period (β = -0.7% per month; P = .03). Most hospitals reduced pharmacologic treatment (8 of 11; 73%) and NICU use (10 of 11; 91%) postguidelines.

CONCLUSIONS

There was a reduction in the use of pharmacologic treatment and NICU utilization for infants with NOWS after the release of American Academy of Pediatrics guidelines for NOWS management.

Advances in animal models of prenatal opioid exposure

Neonatal opioid withdrawal syndrome (NOWS) is a growing public health concern. The complexity of in utero opioid exposure in clinical studies makes it difficult to investigate underlying mechanisms that could ultimately inform early diagnosis and treatments. Clinical studies are unable to dissociate the influence of maternal polypharmacy or the environment from direct effects of in utero opioid exposure, highlighting the need for effective animal models. Early animal models of prenatal opioid exposure primarily used the prototypical opioid, morphine, and opioid exposure that was often limited to a narrow period during gestation. In recent years, the number of preclinical studies has grown rapidly. Newer models utilize both prescription and nonprescription opioids and vary the onset and duration of opioid exposure. In this review, we summarize novel prenatal opioid exposure models developed in recent years and attempt to reconcile results between studies while critically identifying gaps within the current literature.

Decreased myelin-related gene expression in the nucleus accumbens during spontaneous neonatal opioid withdrawal in the absence of long-term behavioral effects in adult outbred CFW mice

Prenatal opioid exposure is a major health concern in the United States, with the incidence of neonatal opioid withdrawal syndrome (NOWS) escalating in recent years. NOWS occurs upon cessation of in utero opioid exposure and is characterized by increased irritability, disrupted sleep patterns, high-pitched crying, and dysregulated feeding. The main pharmacological strategy for alleviating symptoms is treatment with replacement opioids. The neural mechanisms mediating NOWS and the long-term neurobehavioral effects are poorly understood. We used a third trimester-approximate model in which neonatal outbred pups (Carworth Farms White; CFW) were administered once-daily morphine (15 mg/kg, s.c.) from postnatal day (P) day 1 through P14 and were then assessed for behavioral and transcriptomic adaptations within the nucleus accumbens (NAc) on P15. We also investigated the long-term effects of perinatal morphine exposure on adult learning and reward sensitivity. We observed significant weight deficits, spontaneous thermal hyperalgesia, and altered ultrasonic vocalization (USV) profiles following repeated morphine and during spontaneous withdrawal. Transcriptome analysis of NAc from opioid-withdrawn P15 neonates via bulk mRNA sequencing identified an enrichment profile consistent with downregulation of myelin-associated transcripts. Despite the neonatal behavioral and molecular effects, there were no significant long-term effects of perinatal morphine exposure on adult spatial memory function in the Barnes Maze, emotional learning in fear conditioning, or in baseline or methamphetamine-potentiated reward sensitivity as measured via intracranial self-stimulation. Thus, the once daily third trimester-approximate exposure regimen, while inducing NOWS model traits and significant transcriptomic effects in neonates, had no significant long-term effects on adult behaviors.

Neonatal opioid toxicity: opioid withdrawal (abstinence) syndrome with emphasis on pharmacogenomics and respiratory depression

The increasing use of opioids in pregnant women has led to an alarming rise in the number of cases of neonates with drug-induced withdrawal symptoms known as neonatal opioid withdrawal syndrome (NOWS). NOWS is a toxic heterogeneous condition with many neurologic, autonomic, and gastrointestinal symptoms including poor feeding, irritability, tachycardia, hypertension, respiratory defects, tremors, hyperthermia, and weight loss. Paradoxically, for the management of NOWS, low doses of morphine, methadone, or buprenorphine are administered. NOWS is a polygenic disorder supported by studies of genomic variation in opioid-related genes. Single-nucleotide polymorphisms (SNPs) in CYP2B6 are associated with variations in NOWS infant responses to methadone and SNPs in the OPRM1, ABCB1, and COMT genes are associated with need for treatment and length of hospital stay. Epigenetic gene changes showing higher methylation levels in infants and mothers have been associated with more pharmacologic treatment in the case of newborns, and for mothers, longer infant hospital stays. Respiratory disturbances associated with NOWS are not well characterized. Little is known about the effects of opioids on developing neonatal respiratory control and respiratory distress (RD), a potential problem for survival of the neonate. In a rat model to test the effect of maternal opioids on the developing respiratory network and neonatal breathing, maternal-derived methadone increased apneas and lessened RD in neonates at postnatal (P) days P0 and P1. From P3, breathing normalized with age suggesting reorganization of respiratory rhythm-generating circuits at a time when the preBötC becomes the dominant inspiratory rhythm generator. In medullary slices containing the preBötC, maternal opioid treatment plus exposure to exogenous opioids showed respiratory activity was maintained in younger but not older neonates. Thus, maternal opioids blunt centrally controlled respiratory frequency responses to exogenous opioids in an age-dependent manner. In the absence of maternal opioid treatment, exogenous opioids abolished burst frequencies at all ages. Prenatal opioid exposure in children stunts growth rate and development while studies of behavior and cognitive ability reveal poor performances. In adults, high rates of attention deficit disorder, hyperactivity, substance abuse, and poor performances in intelligence and memory tests have been reported.

Decreased myelin-related gene expression in the nucleus accumbens during spontaneous neonatal opioid withdrawal in the absence of long-term behavioral effects in adult outbred CFW mice

Prenatal opioid exposure is a major health concern in the United States, with the incidence of neonatal opioid withdrawal syndrome (NOWS) escalating in recent years. NOWS occurs upon cessation of in utero opioid exposure and is characterized by increased irritability, disrupted sleep patterns, high-pitched crying, and dysregulated feeding. The main pharmacological strategy for alleviating symptoms is treatment with replacement opioids. The neural mechanisms mediating NOWS and the long-term neurobehavioral effects are poorly understood. We used a third trimester-approximate model in which neonatal outbred pups (Carworth Farms White; CFW) were administered once-daily morphine (15 mg/kg, s.c.) from postnatal day (P) day 1 through P14 and were then assessed for behavioral and transcriptomic adaptations within the nucleus accumbens (NAc) on P15. We also investigated the long-term effects of perinatal morphine exposure on adult learning and reward sensitivity. We observed significant weight deficits, spontaneous thermal hyperalgesia, and altered ultrasonic vocalization (USV) profiles following repeated morphine and during spontaneous withdrawal. Transcriptome analysis of NAc from opioid-withdrawn P15 neonates via bulk mRNA sequencing identified an enrichment profile consistent with downregulation of myelin-associated transcripts. Despite the neonatal behavioral and molecular effects, there were no significant long-term effects of perinatal morphine exposure on adult spatial memory function in the Barnes Maze, emotional learning in fear conditioning, or in baseline or methamphetamine-potentiated reward sensitivity as measured via intracranial self-stimulation. Thus, the once daily third trimester-approximate exposure regimen, while inducing NOWS model traits and significant transcriptomic effects in neonates, had no significant long-term effects on adult behaviors.

HIGHLIGHTS

We replicated some NOWS model traits via 1x-daily morphine (P1-P14).We found a downregulation of myelination genes in nucleus accumbens on P15.There were no effects on learning/memory or reward sensitivity in adults.

Potential problems and solutions of opioid-based treatment in neonatal opioid withdrawal syndrome (NOWS): a scoping review protocol

INTRODUCTION

Rates of neonatal opioid withdrawal syndrome (NOWS) have paralleled the rise of opioid use during pregnancy. While short-term phenotypic symptoms of NOWS are well defined, molecular implications and long-term effects are not well understood. Preferred and first-line of treatment for NOWS includes non-pharmacological interventions; however, more than half of the NOWS neonates will need pharmacologics, with opioids as the primary pharmacological treatment. While effective at reducing symptoms, treating NOWS with opioids is paradoxical given that molecular and long-term developmental consequences with such exposure are unknown. There is a pressing need for a synthesis of current and potential/ novel treatment options for NOWS.

METHODS AND ANALYSIS

Following a published framework, a scoping review will be conducted to evaluate NOWS treatment, including established treatment methods and novel methods that may warrant future research and consideration. Using broad search terms, as well as Medical Subject Headings terms, a comprehensive search of PubMed, Cochrane Library, Google Scholar, CINAHL, Web of Science and Scopus, as well as references of selected literature, will take place, followed by a screening procedure to identify included and excluded articles. Included studies must address NOWS treatment, or opioid withdrawal treatment of any age group, that may or may not have been tested in preclinical or clinical models. Results will summarise the current pharmacological and non-pharmacological treatment methods for NOWS, as well as potential novel treatments with a specific interest in non-opioid pharmacological interventions.

ETHICS AND DISSEMINATION

This scoping review aims to broadly search preclinical and clinical literature as it relates to treatment of NOWS, including potential novel treatments with a specific interest in non-opioid pharmacological interventions. Given that this study does not directly involve human subjects or animal subjects research, Institutional Review Board (IRB) or Institutional Animal Care and Use Committee (IACUC) approval is not required. Results of this scoping review will be disseminated at conferences and submitted for publication in a peer-reviewed journal.

Do small for gestational age infants have less severe neonatal abstinence syndrome?

BACKGROUND

Small for gestational age (SGA) infants are likely to have decreased placental transfer of opioids and other substances and lower amounts of fat deposition, hence less severe neonatal abstinence syndrome (NAS). The goal of this study is to correlate SGA status and severity of NAS in infants admitted to the neonatal intensive care unit (NICU).

METHODS

This is a retrospective analysis of term and late-preterm infants (≥35 weeks gestation) exposed to in-utero substances, born between September 2006 and May 2021, and admitted to an inner-city NICU for medical therapy for NAS. Indicators of the severity of NAS (duration of medical treatment, duration of hospitalization, use of phenobarbital, and use of clonidine) were compared between infants characterized as SGA (birth weight <10th percentile for gestational age) to those not categorized as SGA (non-SGA).

RESULTS

A total of 992 infants met the study criteria; 205 (20.7%) in the SGA group and 787 (79.3%) in the non-SGA group. The median duration of medical treatment was significantly lower in infants in the SGA group (22 days vs. 26 days, p = 0.04) and they were less likely to be treated with phenobarbital (19% vs. 26.8%, p = 0.02).

CONCLUSION

SGA infants displayed less severe NAS symptoms as indicated by shorter a duration of medical treatment and decreased need for phenobarbital. Our findings may impact decisions around identifying the optimum treatment protocols catered to SGA infants with NAS.

In Silico Modeling for Ex Vivo Placental Transfer of Morphine

Morphine may be administered in pregnant women as an analgesic agent. The transplacental pharmacokinetics (PK) of morphine varies during pregnancy because of physiological and metabolic changes. In this work, we use a multi-compartment model to simulate ex vivo human placental transfer studies of morphine. The computational model is based on a recently published model for metformin with both passive and active transport kinetics. Modifications were made to incorporate morphine-specific transfer parameters. Parameters for the PK models were determined via the nonlinear regression method. In addition, the Latin hypercube sampling (LHS) method was used for the global parameter analysis of the model. Simulation results show good agreement between the model and observed fetal and maternal morphine concentrations. In addition, the lower efflux of morphine from fetal to maternal plasma reflects reduced P-glycoprotein (P-gp) transport as pregnancy progresses, which leads to slower clearance of morphine in the maternal plasma. The LHS analysis also indicates the more significant roles played by the passive diffusion parameters than the active transport parameter on the fetal/maternal morphine concentrations. In conclusion, we used an in silico model to investigate the transplacental properties of morphine and to predict the in vivo transplacental properties of morphine when PK parameters change.

Physiologic dysregulation in newborns with prenatal opioid exposure: Cardiac, respiratory and movement activity

BACKGROUND

Newborns with prenatal opioid exposure (POE) are commonly diagnosed with neonatal abstinence/opioid-withdrawal syndromes due to characteristic symptoms and overt behaviors. However, little is known about the underlying physiology of opioid-exposed newborns.

OBJECTIVE

Cardiac, respiratory and movement activity were measured to identify physiologic dysregulation and quantify pathophysiologic instabilities of the central and autonomic nervous systems in POE newborns.

METHODS

In this pilot study, 30 hospitalized POE newborns (>35 wks gestational age) participated in one of two study phases wherein physiologic activity was measured for an 8-10 h session. In Phase 1, 17 infants received usual treatment to provide a general assessment of physiologic activity. In Phase 2, 13 infants participated in an interventional study (NCT02768844) using a prototype mattress that delivered stochastic vibratory stimulation (SVS). Changes in physiologic activity were compared for device on (N) and off (F) for three interfeed periods (FNF or NFN).

RESULTS

Phase 1 showed that although infants' heart rate was on average within normal newborn range (mean 137 bpm, SD 7), infants were tachycardic 16% of the study period and tachypneic (mean 74 breaths/min, SD 13) 62% of the period. Infants moved 33% of the period; 17% were durations >30 s. In Phase 2, heart rate, respiratory rate, movement duration and frequency were each reduced for SVS N compared to SVS F in the FNF protocol (P < 0.05).

CONCLUSION

Findings support that physiologic measures can identify dysregulation not captured with current withdrawal scoring assessments. Larger studies are warranted to assess if mattress SVS helps regulate pathophysiologic instabilities in infants with POE.

Assessing waivered and non-waivered physician barriers to treating patients with substance use disorders: a cross-sectional Kentucky pilot

INTRODUCTION

Opioid and other substance use disorders (OUD/SUDs) have been and continue to be significant public health issues. The standard of care for OUD is the use of medication for opioid use disorder (MOUD) in conjunction with counseling or behavioral therapies, yet research has indicated that barriers exist for patients accessing MOUD as well as for physicians prescribing MOUD due to requirements associated with the DATA 2000 waiver.

METHODS

A pilot cross-sectional survey was conducted among Kentucky physicians in order to reassess common barriers as well as to explore barriers that non-waivered providers face to becoming waivered. Barriers were compared by waiver status (waiver vs. non-waivered) as well as geographic location (rural vs. non-rural).

RESULTS

Compared to waivered physicians, non-waivered physicians were significantly less likely to report positive personal beliefs related to the use of MOUD for OUD and reported significantly more barriers to treating OUD patients in the areas of physicians' practice and culture, auditing, and institutional support and resources (p < .05). The majority (69%) of all physicians indicated they would benefit from a tool kit with evidence-based clinical guidelines.

CONCLUSIONS

The barriers and beliefs identified in this pilot study indicate the need for policy action at the federal level to reduce barriers and incentivize more physicians to obtain waivers to treat OUD. Further, the development of brief educational resources tailored to physicians to treat OUD patients including pregnant patients with OUD is recommended.

Economic Evaluation of Interventions for Treatment of Neonatal Opioid Withdrawal Syndrome: A Review

This study assessed the economic evidence on the pharmacological and non-pharmacological management of infants with neonatal opioid withdrawal syndrome (NOWS). Six databases were searched up to October 2020 for peer-reviewed studies. After titles and abstracts were screened, 79 studies remained for full-text review, and finally, 8 studies were eligible for inclusion in the review. The methodological quality of included studies was assessed using the Drummond checklist. The review showed significant limitations in these studies, with one study being rated as good and the remaining seven studies as of poor quality. There are methodological issues that require addressing, including a lack of detail on cost categories, a robust investigation of uncertainty, and extending the time horizon to consider longer-term outcomes beyond the initial birth hospitalization. Despite these limitations, existing evidence suggests non-pharmacological strategies such as rooming-in were associated with a shorter hospital stay and a decreased need for pharmacological treatment, thereby lowering hospitalization costs. The review highlights the paucity of high-quality studies assessing the cost-effectiveness of intervention strategies for NOWS. There is also a lack of evidence on long-term outcomes associated with NOWS and the treatment of NOWS. The inclusion of economic analyses in future studies will provide evidence to inform policymakers on resource allocation decisions for this patient population.

Use of Phenobarbital to Treat Neonatal Abstinence Syndrome From Exposure to Single vs. Multiple Substances

Drug use in pregnancy is a major public health issue. Intrauterine exposure to opioids alone or in addition to other substances may lead to neonatal abstinence syndrome (NAS). Little consensus exists on optimal therapy, especially for those exposed to multiple drugs. We aim to determine whether the use of opioids alone vs. in combination with phenobarbital will affect short-term neonatal outcomes. This retrospective review of infants admitted to the neonatal intensive care unit (NICU) included newborns ≥35 weeks of gestation exposed to opioids, or multiple substances including opioids, in utero. Treatment with opioids alone, and addition of phenobarbital as initial therapy vs. rescue, was evaluated. Out of 182 newborns, 54 (30%) were exposed to methadone alone vs. 128 (70%) to multiple drugs. Length of stay (LOS) in the hospital was not significantly affected (p = 0.684) by single vs. multiple drug exposure in utero. Treatment of NAS with opioid alone resulted in significantly shorter LOS (27 days), as compared to those treated with opioid and phenobarbital (45 days, p < 0.001). LOS was further prolonged in those treated with phenobarbital as a "rescue" medication in addition to an opioid (49 days, p < 0.0001). There was a significant increase in LOS and duration of opioid treatment for all infants treated with phenobarbital, both in those exposed to opioids alone, and to multiple substances in utero.