Analgesia, Opioids, and Other Drug Use During Pregnancy and Neonatal Abstinence Syndrome

Drug-induced fetal and offspring disorders, beyond birth defects

Studies on drug utilization in western countries disclosed that about nine over ten women use at least one or more drugs during pregnancy. Determining whether a drug is safe or not in pregnant women is a challenge of all times. As a developing organism, the fetus is particularly vulnerable to effects of drugs used by the mother. Historically, research has predominantly focused on birth defects, which represent the most studied adverse pregnancy outcomes. However, drugs can also alter the ongoing process of pregnancy and impede the general growth of the fetus. Finally, adverse drug reactions can theoretically damage all developing systems, organs or tissues, such as the central nervous system or the immune system. This extensive review focuses on different aspects of drug-induced damages affecting the fetus or the newborn/infant, beyond birth defects, which are not addressed here.

New insights into the physiology and pathophysiology of the atypical sodium leak channel NALCN

Cell excitability and its modulation by hormones and neurotransmitters involve the concerted action of a large repertoire of membrane proteins, especially ion channels. Unique complements of coexpressed ion channels are exquisitely balanced against each other in different excitable cell types, establishing distinct electrical properties that are tailored for diverse physiological contributions, and dysfunction of any component may induce a disease state. A crucial parameter controlling cell excitability is the resting membrane potential (RMP) set by extra- and intracellular concentrations of ions, mainly Na+, K+, and Cl-, and their passive permeation across the cell membrane through leak ion channels. Indeed, dysregulation of RMP causes significant effects on cellular excitability. This review describes the molecular and physiological properties of the Na+ leak channel NALCN, which associates with its accessory subunits UNC-79, UNC-80, and NLF-1/FAM155 to conduct depolarizing background Na+ currents in various excitable cell types, especially neurons. Studies of animal models clearly demonstrate that NALCN contributes to fundamental physiological processes in the nervous system including the control of respiratory rhythm, circadian rhythm, sleep, and locomotor behavior. Furthermore, dysfunction of NALCN and its subunits is associated with severe pathological states in humans. The critical involvement of NALCN in physiology is now well established, but its study has been hampered by the lack of specific drugs that can block or agonize NALCN currents in vitro and in vivo. Molecular tools and animal models are now available to accelerate our understanding of how NALCN contributes to key physiological functions and the development of novel therapies for NALCN channelopathies.

Early Identification of Atypical Motor Performance of Infants With Prenatal Opioid Exposure

PURPOSE

To investigate the association between prenatal opioid exposure (POE) and newborn infants' motor performance to aid in the early identification of developmental delays.

METHODS

Nineteen infants with POE requiring pharmacological treatment, 27 infants with POE without pharmacological treatment, and 25 infants without POE were assessed via the Test of Infant Motor Performance (TIMP).

RESULTS

Infants in both groups with POE had lower TIMP scores than infants without POE. There was no difference between the TIMP scores of infants with POE who required pharmacological treatment and infants with POE who did not require pharmacological treatment.

CONCLUSIONS

The TIMP can detect differences in motor performance of infants with POE. Regardless of whether infants required pharmacological treatment, POE was associated with lower motor performance. Those working in hospital or early intervention settings can use the TIMP to identify early delays in infants with POE and refer for intervention.

Licit and illicit drug use across trimesters in pregnant women endorsing past-year substance use: Results from National Survey on Drug Use and Health (2009-2019)

PURPOSE

Given the health consequences, perinatal substance use is a significant public health concern, especially as substance use rates increase among women; ongoing data regarding the rates of substance use across trimesters of pregnancy is needed.

METHODS

The present study utilized cross-sectional population-based data from the National Survey of Drug Use and Health (NSDUH) between 2009 and 2019. We aimed to explore both licit and illicit substance use assessed within each trimester among women endorsing past-year substance use. The NSDUH sample included 8,530 pregnant women.

RESULTS

Perinatal substance use was less prevalent among women in later trimesters; however, past-month substance use was observed for all substances across trimesters. The prevalence of past-month licit substance use among pregnant women ranged from 5.77 to 22.50% and past-month illicit substance use ranged from 4.67 to 14.81%. In the second trimester, lower odds of past-month substance use were observed across tobacco, alcohol, and marijuana (odds ratios [ORs] ranging from 0.29 to 0.47), when compared to the first trimester. A similar lower rate of past-month substance use was observed in the third trimester compared to the first trimester, across tobacco, alcohol, and marijuana use, as well as cocaine, prescription pain medication, and tranquilizer use (ORs ranging from 0.02 to 0.42). The likelihood of polysubstance use was lower among women in the second and third trimesters compared to the first trimester (ORs ranging from 0.09 to 0.46).

CONCLUSION

Findings indicate that a minority of women continue to use substances across all trimesters. This is especially true among women using licit substances and marijuana. These results highlight the need for improved interventions and improved access to treatment for these women.

Risk Factors Associated with Perinatal Relapse to Opioid Use Disorder

The recent opioid epidemic in the United States has led to rising prevalence of maternal opioid use disorder (OUD). First-line treatment for maternal OUD involves the use of opioid agonist pharmacotherapy, such as methadone or buprenorphine, in addition to cognitive behavioral therapy and counseling. The management of maternal OUD can become overwhelming for both patients and clinicians, especially during the early postpartum period. Therefore, it is imperative that clinicians understand the impact of additional stressors in caring for these patients. Maternal chronic opioid dependence can lead to neonatal opioid withdrawal syndrome after birth. This multisystem condition affects neonatal neurobehavioral functioning and has significant human and socioeconomic consequences. First-line treatment for this syndrome involves intensive nonpharmacologic comforting measures, with maternal presence and involvement being central to ensuring the success of such measures. In this review, we describe the factors that place pregnant and postpartum women with OUD at risk of returning to illicit opioid use. We evaluate these multifaceted personal, social, societal, and systemic factors to inform the development of future clinical care initiatives.

Neonatal opioid withdrawal syndrome: a review of the science and a look toward the use of buprenorphine for affected infants

Neonates born to mothers taking opioids during pregnancy are at risk for neonatal opioid withdrawal syndrome (NOWS), for which there is no recognized standard approach to care. Nonpharmacologic treatment is typically used as a first-line approach for management, and pharmacologic treatment is added when clinical signs are not responding to nonpharmacologic measures alone. Although morphine and methadone are the most commonly used pharmacotherapies for NOWS, buprenorphine has emerged as a treatment option based on its pharmacologic profile and results from initial single site clinical trials. The objective of this report is to provide an overview of NOWS including a summary of ongoing work in the field and to review the state of the science, knowledge gaps, and practical considerations specific to the use of buprenorphine for the treatment of NOWS as discussed by a panel of experts during a virtual workshop hosted by the National Institutes of Health.

Reconceptualizing non-pharmacologic approaches to Neonatal Abstinence Syndrome (NAS) and Neonatal Opioid Withdrawal Syndrome (NOWS): A theoretical and evidence-based approach. Part II: The clinical application of nonpharmacologic care for NAS/NOWS

There has been increasing emphasis on the importance of the development of self-regulatory capacities of the individual as the cornerstone of development. The caregivers' abilities to manage their own attention, emotions, physiology and behaviors influence the development of the child's self-regulatory and interactive capacities, and thereby their overall development. Newborns prenatally exposed to psychoactive substances and/or to other prenatal stressors such as maternal poor nutrition, increased maternal stress, trauma, difficult and/or impoverished environments, in tandem with genetic predispositions, can result in alterations to their neurodevelopment that predispose them to self-regulatory problems that can be expressed at any stage of life. The care of infants with Neonatal Abstinence Syndrome (NAS)/Neonatal Opioid Withdrawal Syndrome (NOWS) and their mother/caregiver is a window of opportunity to assess the regulatory and co-regulatory capacities of both, and to provide holistic interventions with the goal of empowering the mother/caregiver in their own self-knowledge/self-regulation capacities and their crucial role in promoting the healthy development of their children. Non-pharmacologic care for the infant with NAS/NOWS is the first line of treatment and of paramount importance. Yet, current approaches are based on a limited scope of infant functioning, and the scoring systems in current use do not result in individualized and specific non-pharmacologic care of the infant, which can result in excessive or insufficient medication and a lack of caregiver appreciation for the infant's strengths, difficulties and early development. The interventions described here are based on the infant's signs of dysregulation in four neurobehavioral subsystems that can be dysregulated by NAS/NOWS, the infant's adaptive or maladaptive responses to return to a regulated functioning, and the co-regulatory behaviors of the infant and the mother/caregiver. In Part I of this two-part series on re-conceptualizing non-pharmacologic care for NAS/NOWS we laid the foundation for a new treatment approach, one grounded in developmental theory and evidence-based observations of infant and interpersonal neurobiology. Here, in Part II, we outline actionable, individually tailored evaluations and approaches to non-pharmacologic NAS/NOWS treatment based on strategies to support the regulatory capacities and development of 4 key domains: 1) autonomic; 2) motor/tone; 3) sleep/awake state control; and 4) sensory modulation subsystems.

Pharmacometric dose optimization of buprenorphine in neonatal opioid withdrawal syndrome

Results from Blinded Buprenorphine OR Neonatal morphine solution (BBORN), a previous phase III trial in infants with neonatal opioid withdrawal syndrome (NOWS), demonstrated that sublingual buprenorphine resulted in a shorter duration of treatment and shorter length of hospital stay than the comparator, oral morphine. Objectives of Buprenorphine Pharmacometric Open Label Research study of Drug Exposure (BPHORE), a new trial with buprenorphine in a similar population, were to (1) optimize initial dose, up-titration to achieve symptom control and weaning steps of pharmacologic treatment and (2) investigate safety of the revised regimen. A pharmacodynamic model linked buprenorphine exposure to NOWS symptom scores. Adaptive dose regimens were simulated using BBORN results to compare dosing regimens for times to stabilization, weaning, and cessation. A clinical trial using model informed doses (BPHORE), was conducted. Simulations indicated benefits in time to stabilization and weaning when up-titration rates increased to 30%. Stabilization time was not greatly impacted by the starting dose. Time to wean and time to cessation were dose dependent. A weaning rate of 25% shortened time to cessation. Ten infants were enrolled in BPHORE using buprenorphine starting dose of 24 µg/kg/day, 33% titration, and 15% wean rate. Five subjects required adjuvant therapy. Half-maximal effective concentration (EC₅₀ ) values indicated maximum buprenorphine doses did not generate maximal effect size, suggesting potential efficacy of a further increased dose if a goal was to reduce the use of adjunct agents. Simulations indicated that further benefits can be gained by increasing starting doses of buprenorphine and increasing wean rates. Use of a model-based analysis to provide focused guidelines for care can be used with goals of reducing treatment time and hospital stays in infants with NOWS.

Rapid Induction Therapy for Opioid-Use Disorder Using Buprenorphine Transdermal Patch: A Case Series

INTRODUCTION

Opioid dependency is a major epidemiologic problem with profound morbidity and mortality. Despite the availability of effective treatments, there are often overwhelming barriers to those treatments.

CASE PRESENTATIONS

We present a case series involving a novel approach to the induction phase of buprenorphine or buprenorphine-naloxone therapy using transdermal buprenorphine. This approach has been demonstrated in inpatient settings but has not been widely explored in the outpatient setting. We demonstrated that a range of patients, from the highly medically complex to relatively straightforward cases, benefited from this approach.

DISCUSSION

We believe that this approach can be used in a wide range of patients to transition from opioid use to buprenorphine therapy without the patient having to experience withdrawal or wait to start treatment. This should reduce the risk of lack of return for follow-up as well as decrease the dropout rate caused by patients being unable to tolerate withdrawal symptoms.

Monitoring Prenatal Exposure to Buprenorphine and Methadone

PURPOSE

Buprenorphine and methadone are international gold standards for managing opioid use disorders. Although they are efficacious in treating opioid dependence, buprenorphine and methadone present risks, especially during pregnancy, causing neonatal abstinence syndrome and adverse obstetrical outcomes. Buprenorphine and methadone are also abused during pregnancy, and identifying their use is important to limit unprescribed prenatal exposure. Previous studies have suggested that concentrations of buprenorphine, but not methadone markers in unconventional matrices may predict child outcomes, although currently only limited data exist. We reviewed the literature on concentrations of buprenorphine, methadone, and their metabolites in unconventional matrices to improve data interpretation.

METHODS

A literature search was conducted using scientific databases (PubMed, Scopus, Web of Science, and reports from international institutions) to review published articles on buprenorphine and methadone monitoring during pregnancy.

RESULTS

Buprenorphine and methadone and their metabolites were quantified in the meconium, umbilical cord, placenta, and maternal and neonatal hair. Methadone concentrations in the meconium and hair were typically higher than those in other matrices, although the concentrations in the placenta and umbilical cord were more suitable for predicting neonatal outcomes. Buprenorphine concentrations were lower and required sensitive instrumentation, as measuring buprenorphine glucuronidated metabolites is critical to predict neonatal outcomes.

CONCLUSIONS

Unconventional matrices are good alternatives to conventional ones for monitoring drug exposure during pregnancy. However, data are currently scarce on buprenorphine and methadone during pregnancy to accurately interpret their concentrations. Clinical studies should be conducted with larger cohorts, considering confounding factors such as illicit drug co-exposure.

Utilizing Pediatric Physiologically Based Pharmacokinetic Models to Examine Factors That Contribute to Methadone Pharmacokinetic Variability in Neonatal Abstinence Syndrome Patients

Chronic intrauterine exposure to psychoactive drugs often results in neonatal abstinence syndrome (NAS). NAS is the symptomatic drug withdrawal in newborns that generally occurs after in utero chronic opioid exposure. Methadone is an opioid analgesic commonly prescribed for pharmacologic management of NAS. It exhibits high pharmacokinetic (PK) variability. The current study used physiologically based PK modeling to predict the PK profile of methadone in 20 newborns treated for NAS. The physiologically based PK simulations adequately predicted the PK profile of the clinical data for 45% of the patients. Sensitivity analyses were conducted to explore contributing factors to methadone PK variability. The data suggest that P450 enzymatic activity impacts the clearance of methadone in virtual adults and neonates, while the contribution of cardiac output may be negligible. Understanding maturational and/or pharmacogenetic changes in cytochrome P450 enzymatic activity may further explain the large PK variability of methadone in newborns with NAS and will help individualized treatment.

Opioid Use in Pregnancy

PURPOSE OF REVIEW

Perinatal opioid use is a major public health problem and is associated with a number of deleterious maternal and fetal effects. We review recent evidence of perinatal outcomes and treatment of opioid use disorder (OUD) during pregnancy.

RECENT FINDINGS

Opioid exposure in pregnancy is associated with multiple obstetric and neonatal adverse outcomes, with the most common being neonatal opioid withdrawal syndrome (NOWS). Treatment with buprenorphine or methadone is associated with NOWS, but neither medication appears to have significant adverse effects on early childhood development. Buprenorphine appears to be superior to methadone in terms of incidence and severity of NOWS in exposed infants. The long-term effects of opioid exposure in utero have been inconclusive, but recent longitudinal studies point to potential differences in brain morphology that may increase vulnerability to future stressors. Maintenance therapy with methadone or buprenorphine remains the standard of care for pregnant women with OUD given its consistent superiority to placebo in terms of rates of illicit drug use and pregnancy outcomes. New non-pharmacologic management options for NOWS appear promising. Future research is needed to further evaluate the effects of opioid exposure in utero and determine the optimal delivery model for maintenance therapy.