Maternal methadone dose, placental methadone concentrations, and neonatal outcomes

Investigating the neurobiology of maternal opioid use disorder and prenatal opioid exposure using brain organoid technology

Over the past two decades, Opioid Use Disorder (OUD) among pregnant women has become a major global public health concern. OUD has been characterized as a problematic pattern of opioid use despite adverse physical, psychological, behavioral, and or social consequences. Due to the relapsing-remitting nature of this disorder, pregnant mothers are chronically exposed to exogenous opioids, resulting in adverse neurological and neuropsychiatric outcomes. Collateral fetal exposure to opioids also precipitates severe neurodevelopmental and neurocognitive sequelae. At present, much of what is known regarding the neurobiological consequences of OUD and prenatal opioid exposure (POE) has been derived from preclinical studies in animal models and postnatal or postmortem investigations in humans. However, species-specific differences in brain development, variations in subject age/health/background, and disparities in sample collection or storage have complicated the interpretation of findings produced by these explorations. The ethical or logistical inaccessibility of human fetal brain tissue has also limited direct examinations of prenatal drug effects. To circumvent these confounding factors, recent groups have begun employing induced pluripotent stem cell (iPSC)-derived brain organoid technology, which provides access to key aspects of cellular and molecular brain development, structure, and function in vitro. In this review, we endeavor to encapsulate the advancements in brain organoid culture that have enabled scientists to model and dissect the neural underpinnings and effects of OUD and POE. We hope not only to emphasize the utility of brain organoids for investigating these conditions, but also to highlight opportunities for further technical and conceptual progress. Although the application of brain organoids to this critical field of research is still in its nascent stages, understanding the neurobiology of OUD and POE via this modality will provide critical insights for improving maternal and fetal outcomes.

Transplacental methadone exposure and risk of Neonatal Opioid Withdrawal Syndrome

STUDY OBJECTIVE

Neonatal opioid withdrawal syndrome (NOWS) is a condition that often occurs in neonates born to mothers who received methadone treatment for opioid use disorder during pregnancy. Early identification and treatment of infants at risk of NOWS may improve clinical outcomes. The purpose of this study was to evaluate whether maternal and umbilical cord plasma concentrations of methadone and its metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), could predict the need for NOWS treatment.

DESIGN

Single-center prospective study.

SETTING

University of Michigan Neonatal Intensive Care Unit.

PATIENTS

The study included 11 opioid-dependent mother-infant dyads, where the mothers were treated with methadone at 34 weeks' gestation or later.

INTERVENTION

Maternal and cord blood samples were collected from the study participants.

MEASUREMENTS AND MAIN RESULTS

Maternal and cord plasma concentrations of methadone and EDDP were determined. Six out of the 11 infants required treatment for NOWS. Maternal methadone plasma concentrations were comparable between infants requiring and not requiring NOWS treatment (329.1 ± 229.7 ng/mL vs. 413.2 ± 329.8 ng/mL). However, the average cord plasma methadone concentration in infants who did not require NOWS treatment was 2.9-fold higher than in those who required the treatment (120.0 ± 88.6 ng/mL vs. 40.9 ± 24.4 ng/mL), although the difference was not statistically significant. The ratios of maternal-to-cord methadone plasma concentrations were significantly higher in patients who required treatment for NOWS compared with those who did not (7.7 ± 1.9 vs. 3.5 ± 1.6, p = 0.003). Maternal and cord plasma EDDP concentrations and the maternal-to-cord plasma EDDP concentration ratios did not differ between patients who required and did not require treatment for NOWS.

CONCLUSIONS

The results suggest that methadone permeability across the blood-placental barrier may affect in utero exposure to methadone, and the maternal-to-cord methadone plasma concentration ratio could be a potential biomarker for predicting the need for NOWS treatment.

Can umbilical cord testing add to maternal urine drug screen for evaluation of infants at risk of neonatal opioid withdrawal syndrome?

OBJECTIVE

This study evaluated maternal urine drug screen (UDS) at delivery and umbilical cord drug testing and its association with neonatal opioid withdrawal syndrome (NOWS) diagnosis and severity following opioid exposed pregnancy.

METHODS

A retrospective chart review of 770 mother-infant dyads at five birthing hospitals in the United States Appalachian region for a five-year period was performed. Variables of interest included dyad demographics, results of maternal UDS at delivery and umbilical cord drug testing, and three neonatal outcomes: NOWS diagnosis, pharmacologic treatment administered for NOWS, and length of hospital stay (LOS) of the newborn.

RESULTS

Opioid-positivity was between 8.5% and 66.3% based on maternal UDS at delivery or umbilical cord testing. Odds of NOWS diagnosis and increased infant LOS was best associated with opioid detection in maternal UDS alone (OR = 5.62, 95% CI [3.06, 10.33] and OR = 8.33, 95% CI [3.67, 18.89], respectively). However, odds of pharmacologic treatment for NOWS was best associated with opioid detection in both maternal UDS and umbilical cord testing on the same dyad (OR = 3.22, 95% CI [1.14, 9.09]).

CONCLUSION

Maternal UDS is a better option compared to umbilical cord testing for evaluation of opioid-exposed infants and risk of NOWS diagnosis and increased infant LOS.

Methadone alters transcriptional programs associated with synapse formation in human cortical organoids

Opioid use disorder (OUD) among pregnant women has become an epidemic in the United States. Pharmacological interventions for maternal OUD most commonly involve methadone, a synthetic opioid analgesic that attenuates withdrawal symptoms and behaviors linked with drug addiction. However, evidence of methadone's ability to readily accumulate in neural tissue, and cause long-term neurocognitive sequelae, has led to concerns regarding its effect on prenatal brain development. We utilized human cortical organoid (hCO) technology to probe how this drug impacts the earliest mechanisms of cortico-genesis. Bulk mRNA sequencing of 2-month-old hCOs chronically treated with a clinically relevant dose of 1 μM methadone for 50 days revealed a robust transcriptional response to methadone associated with functional components of the synapse, the underlying extracellular matrix (ECM), and cilia. Co-expression network and predictive protein-protein interaction analyses demonstrated that these changes occurred in concert, centered around a regulatory axis of growth factors, developmental signaling pathways, and matricellular proteins (MCPs). TGFβ1 was identified as an upstream regulator of this network and appeared as part of a highly interconnected cluster of MCPs, of which thrombospondin 1 (TSP1) was most prominently downregulated and exhibited dose-dependent reductions in protein levels. These results demonstrate that methadone exposure during early cortical development alters transcriptional programs associated with synaptogenesis, and that these changes arise by functionally modulating extra-synaptic molecular mechanisms in the ECM and cilia. Our findings provide novel insight into the molecular underpinnings of methadone's putative effect on cognitive and behavioral development and a basis for improving interventions for maternal opioid addiction.

A review of the literature: How does prenatal opioid exposure impact placental health and fetal brain development?

In recent years, there has been a sixfold increase in the number of pregnant people with opioid use disorder (OUD). Rates of neonatal opioid withdrawal syndrome (NOWS), previously known as neonatal abstinence syndrome (NAS), have significantly increased in virtually every state and demographic group (Healthcare Cost Utilization Project, HCUP, 2010). NOWS is a condition resulting from chronic exposure to either therapeutic opioid use (e.g., medication for OUD, chronic pain conditions) or nonprescribed opioid use. To date, there is no known prenatal treatment to help decrease the risk of infants developing NOWS and subsequent neurodevelopmental outcomes. Given the increasing support for how placental signaling, or placental programming, may play a role in downstream pathology, prospective research investigating how the placenta is affected by chronic opioid exposure morphologically, histologically, and at the cellular level may open up potential treatment opportunities in this field. In this review, we discuss literature exploring the physiological roles of nitric oxide and dopamine not only in the vascular development of the placenta, but also in fetal cerebral blood flow, neurogenesis, neuronal differentiation, and neuronal activity. We also discuss histological preclinical studies that suggest chronic opioid exposure to induce some combination of placental dysfunction and hypoxia in a manner similar to other well-known placental pathologies, as denoted by the compensatory neovascularization and increased utilization of the placenta's supply of trophoblast cells, which play an essential role in placental angiogenesis. Overall, we found that the current literature, while limited, suggests chronic opioid exposure negatively impacts placental function and fetal brain development on a cellular and histopathological level. We conclude that it is worthwhile to consider the placenta as a therapeutic target with the ultimate goal of decreasing the incidence of NOWS and the long-term impacts of prenatal opioid exposure.

Association of medication-assisted treatment and short acting opioids with newborn head circumference and birth weight

OBJECTIVE

We compared the association of methadone, buprenorphine, and short-acting opioid exposure with newborn head circumference (HC) and birth weight (BW), and evaluated gestational age (GA) as a mediator.

STUDY DESIGN

We included newborns born 2013-2018 identified by neonatal abstinence syndrome diagnosis code (N = 572) and birthday-matched unexposed controls (N = 571). Linear regressions of opioid exposure with HC and BW controlled for tobacco, marijuana, cocaine, gabapentin, cesarean section, Medicaid, and newborn sex, with mediation analysis by GA.

RESULT

Methadone was associated with 0.81 cm lower HC (95% CI = -1.22, -0.40) and 0.23 kg lower BW (95% CI = -0.35, -0.10) with approximately 24% and 41% mediated by GA, respectively. Buprenorphine and short acting opioids were not associated with HC or BW.

CONCLUSION

Methadone exposed newborns have smaller HC and lower BW not fully attributable to younger GA, suggesting a direct effect of methadone on intrauterine growth. Exploration of potential developmental consequences of this is urgently needed.

Drug testing in support of the diagnosis of neonatal abstinence syndrome: The current situation

Illicit drug use during pregnancy is a concern worldwide, with many international studies describing attempted strategies to mitigate this problem. Drug misuse during pregnancy is associated with significant maternal as well as perinatal complications, which include a high incidence of stillbirths, fetal distress, neonatal abstinence syndrome (NAS) and increased neonatal mortality. Unfortunately, the identification of a drug-exposed mother or neonate is challenging. Maternal disclosure of drug use is often inaccurate, principally due to psychosocial factors including behavioral denial or the fear of the consequences resulting from such admissions. Likewise, many infants who have been exposed to drugs in utero may appear normal at birth and initially show no overt manifestations of drug effects. Thus, the identification of the drug-exposed infant requires a high index of clinical suspicion. Conversely, analytical testing is an objective means of determining drug exposure when it may be necessary to document proof of the infant's exposure to illicit drugs. The review will discuss the different matrices that are most commonly used for testing (e.g., maternal urine, neonatal urine, meconium, and umbilical cord), the strengths and limitations for each matrix, which drugs and metabolites are appropriate for testing, the various testing methods, and the advantages and disadvantages of each method.

The placenta as a target of opioid drugs†

Opioid drugs are analgesics increasingly being prescribed to control pain associated with a wide range of causes. Usage of pregnant women has dramatically increased in the past decades. Neonates born to these women are at risk for neonatal abstinence syndrome (also referred to as neonatal opioid withdrawal syndrome). Negative birth outcomes linked with maternal opioid use disorder include compromised fetal growth, premature birth, reduced birthweight, and congenital defects. Such infants require lengthier hospital stays necessitating rising health care costs, and they are at greater risk for neurobehavioral and other diseases. Thus, it is essential to understand the genesis of such disorders. As the primary communication organ between mother and conceptus, the placenta itself is susceptible to opioid effects but may be key to understanding how these drugs affect long-term offspring health and potential avenue to prevent later diseases. In this review, we will consider the evidence that placental responses are regulated through an endogenous opioid system. However, maternal consumption of opioid drugs can also bind and act through opioid receptors express by trophoblast cells of the placenta. Thus, we will also discuss the current human and rodent studies that have examined the effects of opioids on the placenta. These drugs might affect placental hormones associated with maternal recognition of pregnancy, including placental lactogens and human chorionic gonadotropin in rodents and humans, respectively. A further understanding of how such drugs affect the placenta may open up new avenues for early diagnostic and remediation approaches.

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.

Association of Maternal Buprenorphine or Methadone Dose with Fetal Growth Indices and Neonatal Abstinence Syndrome

OBJECTIVE

Our objective was to compare fetal growth and incidence of neonatal abstinence syndrome requiring treatment across pregnant women with opioid use disorders on two types and two dose categories of medication-assisted treatment.

STUDY DESIGN

A retrospective cohort study was conducted in a comprehensive, perinatal program in western North Carolina comparing growth percentiles on third-trimester ultrasound and at birth, and diagnosis of neonatal abstinence syndrome requiring treatment. Singletons were exposed in utero to low- to moderate-dose buprenorphine (≤16 mg/day; n = 70), high-dose buprenorphine (≥17 mg/day; n = 36), low- to moderate-dose methadone (≤89 mg/day; n = 41), or high-dose methadone (≥90 mg/day; n = 74). Multivariate analysis of variance with posthoc Bonferroni comparisons (p ≤ 0.01) and multinomial logistic regressions (adjusted odds ratio, 99% confidence interval) were conducted.

RESULTS

Differences in neonatal outcomes reached statistical significance for larger head circumference for buprenorphine doses (p = 0.01) and for longer length (p < 0.01) and lower odds of neonatal abstinence syndrome requiring treatment (p < 0.01) with low- to moderate-dose buprenorphine versus high-dose methadone.

CONCLUSION

Among pregnant women using medication-assisted treatment for opioid use disorders, low- to moderate-dose buprenorphine (≤16 mg/day) was associated with the most favorable neonatal outcomes. However, more rigorous control of confounders with a larger sample is necessary to determine if low- to moderate-dose buprenorphine is the better treatment choice.

Methadone Suppresses Neuronal Function and Maturation in Human Cortical Organoids

Accumulating evidence has suggested that prenatal exposure to methadone causes multiple adverse effects on human brain development. Methadone not only suppresses fetal neurobehavior and alters neural maturation, but also leads to long-term neurological impairment. Due to logistical and ethical issues of accessing human fetal tissue, the effect of methadone on brain development and its underlying mechanisms have not been investigated adequately and are therefore not fully understood. Here, we use human cortical organoids which resemble fetal brain development to examine the effect of methadone on neuronal function and maturation during early development. During development, cortical organoids that are exposed to clinically relevant concentrations of methadone exhibited suppressed maturation of neuronal function. For example, organoids developed from 12th week till 24th week have an about 7-fold increase in AP firing frequency, but only half and a third of this increase was found in organoids exposed to 1 and 10 μM methadone, respectively. We further demonstrated substantial increases in I_Na (4.5-fold) and I_KD (10.8-fold), and continued shifts of Na⁺ channel activation and inactivation during normal organoid development. Methadone-induced suppression of neuronal function was attributed to the attenuated increase in the densities of I_Na and I_KD and the reduced shift of Na⁺ channel gating properties. Since normal neuronal electrophysiology and ion channel function are critical for regulating brain development, we believe that the effect of prolonged methadone exposure contributes to the delayed maturation, development fetal brain and potentially for longer term neurologic deficits.

Neuroimaging in infants with prenatal opioid exposure: Current evidence, recent developments and targets for future research

Prenatal opioid exposure (POE) has shown to be a risk factor for adverse long-term cognitive and behavioral outcomes in offspring. However, the neural mechanisms of these outcomes remain poorly understood. While preclinical and human studies suggest that these outcomes may be due to opioid-mediated changes in the fetal and early postnatal brain, other maternal, social, and environmental factors are also shown to play a role. Recent neuroimaging studies reveal brain alterations in children with POE. Early neuroimaging and novel methodology could provide an in vivo mechanistic understanding of opioid mediated alterations in developing brain. However, this is an area of ongoing research. In this review we explore recent imaging developments in POE, with emphasis on the neonatal and infant brain, and highlight some of the challenges of imaging the developing brain in this population. We also highlight evidence from animal models and imaging in older children and youth to understand areas where future research may be targeted in infants with POE.

The role of xenobiotic-metabolizing enzymes in the placenta: a growing research field

Introduction: The placenta is a temporary and unique organ that allows for the physical connection between a mother and fetus; this organ regulates the transport of gases and nutrients mediating the elimination of waste products contained in the fetal circulation. The placenta performs metabolic and excretion functions, on the basis of multiple enzymatic systems responsible for the oxidation, reduction, hydrolysis, and conjugation of xenobiotics. These mechanisms give the placenta a protective role that limits the fetal exposure to harmful compounds. During pregnancy, some diseases require uninterrupted treatment even if it is detrimental to the fetus. Drugs and other xenobiotics alter gene expression in the placenta with repercussions for the fetus and mother's well-being.Areas covered: This review provides a brief description of the human placental structure and function, the main drug and xenobiotic transporters and metabolizing enzymes, placenta-metabolized substrates, and alterations in gene expression that the exposure to xenobiotics may cause.Expert opinion: Research should be focused on the identification and validation of biological markers for the assessment of the harmful effects of some drugs in pregnancy, including the evaluation of polymorphisms and methylation patterns in chorionic villous samples and/or amniotic fluid.

The impact of neuropsychiatric disease on fetal growth: a case-control study

PURPOSE

To determine the impact of depression, epilepsy and drug abuse during pregnancy on delivery and fetal outcome. Due to the worldwide increasing prevalence of neurological and psychiatric diseases and drug abuse, the number of affected pregnant women is increasing.

METHODS

A large-scale retrospective case-control analysis of pregnancies affected by depression, epilepsy or drug abuse with and without medication was conducted in two German perinatal centres between 2013 and 2017. The case group consisted of 706 pregnant women who had a diagnosis of depression, epilepsy or drug abuse vs. 12,574 pregnant women without neuropsychiatric diagnosis (control group). The analysis included the rate of intrauterine growth restriction, birth weight and length, neonatal head circumference.

RESULTS

Significant differences in the subgroups were found in the parameters intrauterine growth restriction, birth weight, length and head circumference. Women with epilepsy were affected less often than women with depression and substance abuse. Major differences were found in the group of women with substance abuse. Negative associations were found within the non-pharmacologically managed disease group itself compared to women exposed to medication.

CONCLUSION

The present results demonstrated a negative association between maternal neurological or psychiatric disease and pregnancy outcome in the examined parameters. However, the non-pharmacologically treated maternal disease was identified as a risk factor itself.

Risk Factors Associated with the Occurrence of Neonatal Opioid Withdrawal Syndrome: A Review

In a number of countries, the prevalence of neonatal opioid withdrawal syndrome (NOWS) is increasing. While NOWS is ultimately the result of opioid exposure in utero, a wide range of risk factors have been associated with the prevalence of NOWS, extending beyond just drug exposure. This article reviews the available literature on factors associated with the incidence of NOWS in opioid-exposed neonates. A range of risk factors have been associated with NOWS, including features of neonatal drug exposure, maternal and neonatal characteristics, aspects of labor and delivery, and genetics. Increased length of gestation and higher birth weight were consistently associated with an increased risk of NOWS, while breast feeding and 'rooming-in' were associated with a reduced risk of NOWS. Additionally, several genetic factors have also been associated with NOWS severity. There is conflicting evidence on the association between NOWS and other risk factors including opioid dose, neonate sex, and the use of some medications during pregnancy. This may be in part attributable to differences in how NOWS is diagnosed and the variety of methodologies across studies. While a large number of risk factors associated with NOWS are non-modifiable, encouraging pregnant women to reduce other drug use (including smoking), breast feed their child, and the judicious use of medications during pregnancy may help reduce the prevalence of NOWS. The presence or absence of NOWS in an opioid-exposed neonate is associated with a wide range of factors. Some of these modifiable risk factors may be potential targets for the primary prevention of NOWS.

A Sensitive LC-MS/MS Assay for the Quantification of Methadone and its Metabolites in Dried Blood Spots: Comparison With Plasma

INTRODUCTION

Methadone, a synthetic narcotic, is widely used both in adults and children for pain control and as a replacement drug in opioid use disorder to prevent craving and withdrawal. To support clinical pharmacokinetic trials in neonates, infants, and children, the authors developed and validated a novel, automated, highly sensitive liquid chromatography-electrospray-tandem mass spectrometry ionization (LC-ESI-MS/MS) method for the quantification of methadone and its metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenylpyraline (EMDP), in samples collected as dried blood spots.

METHODS

Blood was spiked with different concentrations of methadone, EDDP, and EMDP, and blood drops were applied to filter paper cards. Punches of 6.4 mm were removed from the cards, and 600 µL of protein precipitation solution (methanol/0.2M ZnSO4, 7:3, vol/vol) containing the internal standards (methadone-d9 and EDDP-d5) at a concentration of 1 mcg/L was added. The extracts were analyzed using LC-ESI-MS/MS in combination with online extraction. The mass spectrometer was run in the positive multiple reaction monitoring mode, and the total run time was 3.2 minutes.

RESULTS

For the dried blood spots, the assay has a lower limit of quantification of 0.1 mcg/L for methadone, EDDP, and EMDP. The range of reliable response for methadone for the ion transition m/z = 310.2→265.1 was 0.1-100 mcg/L and for the ion transition m/z = 310.2→223.1 5-1000 mcg/L. For EDDP, on the range of reliable response for the ion transition, m/z = 278.2→234.3 was 0.1-100 mcg/L and for the ion transition m/z = 278.2→186.1 5-1000 mcg/L. The calibration range for EMDP was 0.1-100 mcg/L. Accuracy (85%-115%) and imprecision (<15%) met predefined acceptance criteria.

DISCUSSION

This assay allows for the measurement of small volume blood samples without the need for an intravenous blood draw, and thus, it is suitable for pharmacokinetics studies and therapeutic drug monitoring in pediatric patients.

Neonatal abstinence syndrome

Neonates exposed prenatally to opioids will often develop a collection of withdrawal signs known as neonatal abstinence syndrome (NAS). The incidence of NAS has substantially increased in recent years placing an increasing burden on the healthcare system. Traditional approaches to assessment and management have relied on symptom-based scoring tools and utilization of slowly decreasing doses of medication, though newer models of care focused on non-pharmacologic interventions and rooming-in have demonstrated promise in reducing length of hospital stay and medication usage. Data on long-term outcomes for both traditional and newer approaches to care of infants with NAS is limited and an important area of future research. This review will examine the history, incidence and pathophysiology of NAS. We will also review diagnostic screening approaches, scoring tools, differing management approaches and conclude with recommendations for continued work to improve the care of infants with NAS.

Neonatal abstinence syndrome

Neonatal abstinence syndrome refers to the signs and symptoms attributed to the cessation of prenatal exposure (via placental transfer) to various substances. This Primer focuses on neonatal abstinence syndrome caused by opioid use during pregnancy - neonatal opioid withdrawal syndrome (NOWS). As the global prevalence of opioid use has alarmingly increased, so has the incidence of NOWS. NOWS can manifest with varying severity or not at all, for unknown reasons, but is likely to be associated with multiple factors, both maternal (for example, smoking and additional substance exposures) and neonatal (gestational age, sex and genetics). Care for the infant with NOWS begins with addressing the issues experienced by pregnant women with opioid use disorder. Co-occurring mental illness, economic hardship, intimate partner violence, infectious diseases and limited access to care are common in these women and can result in poor maternal and neonatal outcomes. Although there is no consensus regarding optimal NOWS management, non-pharmacological interventions (such as breastfeeding and rooming-in of the mother and the baby) have become a priority, as they can ameliorate symptoms without the need for further opioid exposure. Untreated NOWS can be associated with morbidity in early infancy, and the long-term consequences of fetal opioid exposure are only beginning to be understood.

Screening Pregnant Women and Their Neonates for Illicit Drug Use: Consideration of the Integrated Technical, Medical, Ethical, Legal, and Social Issues

North America is currently suffering from one of the worst epidemics of illicit drug use in recent history: the opioid crisis. Pregnant women are not immune to the ravages of substance misuse which affects themselves, their pregnancies, and the wider community. The prevalence of drug misuse in pregnancy is not well quantified due to the lack of good validated tests, cooperation between clinicians and scientists developing tests, and consensus as to who should be tested and how results should be used. A wide range of tissues can be tested for drug use, including maternal blood, urine, and hair; neonatal meconium, urine, and hair; and placenta and umbilical cord tissues. Testing methods range from simple spectrophotometry and clinical chemistry to sophisticated analytical HPLC or mass spectrometry techniques. The drive for ever greater accuracy and sensitivity must be balanced with the necessities of medical practice requiring minimally invasive sampling, rapid turnaround, and techniques that can be realistically utilized in a clinical laboratory. Better screening tests have great potential to improve neonatal and maternal medical outcomes by enhancing the speed and accuracy of diagnosis. They also have great promise for public health monitoring, policy development, and resource allocation. However, women can and have been arrested for positive drug screens with even preliminary results used to remove children from custody, before rigorous confirmatory testing is completed. Balancing the scientific, medical, public health, legal, and ethical aspects of screening tests for drugs in pregnancy is critical for helping to address this crisis at all levels.

Will Widespread Synthetic Opioid Consumption Induce Epigenetic Consequences in Future Generations?

A growing number of evidence demonstrates that ancestral exposure to xenobiotics (pollutants, drugs of abuse, etc.) can perturb the physiology and behavior of descendants. Both maternal and paternal transmission of phenotype across generations has been proved, demonstrating that parental drug history may have significant implications for subsequent generations. In the last years, the burden of novel synthetic opioid (NSO) consumption, due to increased medical prescription of pain medications and to easier accessibility of these substances on illegal market, is raising new questions first in term of public health, but also about the consequences of the parental use of these drugs on future generations. Besides being associated to the neonatal abstinence syndrome, in utero exposure to opioids has an impact on neuronal development with long-term repercussions that are potentially transmitted to subsequent generations. In addition, recent reports suggest that opioid use even before conception influences the reactivity to opioids of the progeny and the following generations, likely through epigenetic mechanisms. This review describes the current knowledge about the transgenerational effects of opioid consumption. We summarize the preclinical and clinical findings showing the implications for the subsequent generations of parental exposure to opioids earlier in life. Limitations of the existing data on NSOs and new perspectives of the research are also discussed, as well as clinical and forensic consequences.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the determination of nicotine and its metabolites in placenta and umbilical cord

Tobacco exposure during pregnancy is associated with obstetric and fetal complications. We developed and validated a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method to determine nicotine, cotinine, and hydroxycotinine (OH-cotinine) in placenta (PL) and umbilical cord (UC). Specimens were homogenized in water, followed by solid-phase extraction. Chromatographic separation was performed using an Atlantis® HILIC Silica column. Detection was accomplished in electrospray in positive mode. Method validation included: linearity (5 to 1000 ng/g), accuracy (86.9 to 105.2% of target concentration in PL, and 89.1 to 105.0% in UC), imprecision (6.8 to 11.8% in PL, and 7.6 to 12.2% in UC), limits of detection (2 ng/g for cotinine and OH-cotinine, and 5 ng/g for nicotine) and quantification (5 ng/g), selectivity (no endogenous or exogenous interferences), matrix effect (-34.1 to -84.5% in PL, %CV = 9.1-24.0%; -18.9 to -84.7% in UC, %CV = 10.2-23.9%), extraction efficiency (60.7 to 131.5% in PL, and 64.1 to 134.2% in UC), and stability 72 h in the autosampler (<11.5% loss in PL, and < 13% loss in UC). The method was applied to 14 PL and UC specimens from tobacco users during pregnancy. Cotinine (6.8-312.2 ng/g in PL; 6.7-342.3 ng/g in UC) was the predominant analyte, followed by OH-cotinine ( Collapse

Key Words

• LC-MS/MS
• nicotine
• placenta
• tobacco
• umbilical cord

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Affiliation(s)

Lucía Paniagua-González Toxicology Service, Institute of Forensic Sciences, University of Santiago de Compostela, Santiago de Compostela, Spain
Cristian Jiménez-Morigosa Toxicology Service, Institute of Forensic Sciences, University of Santiago de Compostela, Santiago de Compostela, Spain
Elena Lendoiro Toxicology Service, Institute of Forensic Sciences, University of Santiago de Compostela, Santiago de Compostela, Spain School of Pharmacy and Life Sciences, The Robert Gordon University, Aberdeen, UK
Marta Concheiro Department of Sciences, John Jay College of Criminal Justice, City University of New York, New York
Angelines Cruz Toxicology Service, Institute of Forensic Sciences, University of Santiago de Compostela, Santiago de Compostela, Spain
Manuel López-Rivadulla Toxicology Service, Institute of Forensic Sciences, University of Santiago de Compostela, Santiago de Compostela, Spain
Ana de Castro Toxicology Service, Institute of Forensic Sciences, University of Santiago de Compostela, Santiago de Compostela, Spain

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Treating Women Who Are Pregnant and Parenting for Opioid Use Disorder and the Concurrent Care of Their Infants and Children: Literature Review to Support National Guidance

OBJECTIVES

The prevalence of opioid use disorder (OUD) during pregnancy is increasing. Practical recommendations will help providers treat pregnant women with OUD and reduce potentially negative health consequences for mother, fetus, and child. This article summarizes the literature review conducted using the RAND/University of California, Los Angeles Appropriateness Method project completed by the US Department of Health and Human Services Substance Abuse and Mental Health Services Administration to obtain current evidence on treatment approaches for pregnant and parenting women with OUD and their infants and children.

METHODS

Three separate search methods were employed to identify peer-reviewed journal articles providing evidence on treatment methods for women with OUD who are pregnant or parenting, and for their children. Identified articles were reviewed for inclusion per study guidelines and relevant information was abstracted and summarized.

RESULTS

Of the 1697 articles identified, 75 were included in the literature review. The perinatal use of medication for addiction treatment (MAT, also known as medication-assisted treatment), either methadone or buprenorphine, within comprehensive treatment is the most accepted clinical practice, as withdrawal or detoxification risks relapse and treatment dropout. Medication increases may be needed with advancing pregnancy, and are not associated with more severe neonatal abstinence syndrome (NAS). Switching medication prenatally is usually not recommended as it can destabilize opioid abstinence. Postnatally, breastfeeding is seen as beneficial for the infant for women who are maintained on a stable dose of opioid agonist medication. Less is known about ideal pain management and postpartum dosing regimens. NAS appears generally less severe following prenatal exposure to buprenorphine versus methadone. Frontline NAS medication treatments include protocol-driven methadone and morphine dosing in the context of nonpharmacological supports.

CONCLUSIONS

Women with OUD can be treated with methadone or buprenorphine during pregnancy. NAS is an expected and manageable condition. Although research has substantially advanced, opportunities to guide future research to improve maternal and infant outcomes are provided.

Bioanalysis for cocaine, opiates, methadone, and amphetamines exposure detection during pregnancy

Drug exposure during pregnancy constitutes a major legal issue and a public health concern. Drug and metabolite determination in biological matrices from mother and newborn is an objective indication of prenatal drug exposure. However, limited data are available regarding the interpretation of these analytical results in terms of window of detection and degree of exposure. We collected paired maternal hair, meconium, placenta, and umbilical cord from 727 mother-newborn dyads. We analyzed these specimens by liquid chromatography-tandem mass spectrometry for the determination of cocaine, opioids, methadone, and amphetamines, and compared the analytical results from the four different matrices. The cases were divided in non-exposure, low, and frequent exposure, based on maternal hair concentrations and segmental analysis by trimesters. For cocaine, 62 cases tested positive in hair, 9 in meconium, 6 in placenta and 7 in umbilical cord. In the case of opioids, 14 maternal hair cases were positive, 11 meconium and umbilical cord and 9 placenta samples. For methadone, 11 cases were positive in hair, 9 in meconium and 6 in placenta and umbilical cord. For amphetamines, 18 cases were positive according to maternal hair, but all meconium, placenta, and umbilical cord tested negative. Maternal hair was the most sensitive specimen to detect drug exposure during pregnancy. Meconium, placenta, and umbilical cord tested positive if hair concentrations showed frequent drug use during the whole pregnancy, especially during the third trimester. Meconium, placenta, and umbilical cord also tested positive for morphine and metabolites, if this drug was administered during labour and delivery. Copyright © 2016 John Wiley & Sons, Ltd.

Bioanalysis during pregnancy: recent advances and novel sampling strategies

Consumption of drugs of abuse, tobacco and alcohol throughout pregnancy is a serious public health problem and results in an important economic cost to the health system. Drug and/or metabolites determination in biological matrices from mother and newborn is an objective measure of in utero drug exposure. We reviewed methods published for the determination of in utero drug exposure from 2007 to 2014, with special focus on meconium, placenta, umbilical cord and newborn hair. Accurate bioanalytical procedures are essential to obtain high-quality data to perform interventions and to establish correlations between analytical measures and clinical outcomes. We included a brief overview of clinical implications of in utero drug exposure to better understand the importance of this serious health issue.

Oral morphine weaning for neonatal abstinence syndrome at home compared with in-hospital: an observational cohort study

OBJECTIVE

The objective of this observational study was to evaluate the safety and effectiveness of discharging stabilized neonates to complete their oral morphine weaning at home.

STUDY DESIGN

This retrospective cohort study evaluated neonates treated with oral morphine at two hospitals in London, Ontario, Canada. Neonates who completed their morphine wean in hospital were compared with neonates who completed their morphine wean following discharge from hospital (at home).

RESULTS

There were 80 neonates treated with oral morphine at two hospitals from 2006 to 2010. The majority (65%, 52/80) of neonates completed their morphine weaning after hospital discharge and were significantly less likely to return to hospital for further withdrawal treatment (1/52 vs. 4/28, p < 0.05). Neonates who were treated at home remained on morphine for more days (32 vs. 19 days, p < 0.01).

CONCLUSIONS

We present the first North American cohort of neonates weaned with morphine at home for neonatal abstinence syndrome (NAS). We found that more days on oral morphine resulted in fewer returns to hospital for continued withdrawal management. There was no evidence of increased effectiveness, measured by the number of returns to hospital for further NAS management with in-hospital weaning. The estimated cost savings of continued weaning upon discharge was approximately $11,000 per patient (Canadian dollars). While further prospective research is necessary, in some cases morphine weaning at home may present a safe and cost-effective strategy for NAS management.

Beneficial effects of co-treatment with dextromethorphan on prenatally methadone-exposed offspring

Background

Heroin use among young women of reproductive age has drawn much attention around the world. Although methadone is widely used in maintenance therapy for heroin/morphine addiction, the long-term effects of prenatal exposure to methadone and preventative therapy remain unclear. For revealing this question, female pregnant Sprague–Dawley rats were sub-grouped to receive (1) vehicle, (2) methadone 5 mg/kg at embryonic day 3 (E3) and then 7 mg/kg from E4 to E20, (3) dextromethorphan (DM) 3 mg/kg, and (4) methadone + DM (the rats received methadone followed by DM treatment), subcutaneously, twice a day from E3 to E20. The body weight, natural withdrawal, pain sensitivity, ED50, conditioned place preference and water maze were conducted at different postnatal stages (P1 to P79) of offspring. The quantitative real-time RT-PCR and electrophysiology were also used to measure the gene expression of opioid receptors in the spinal cord and changes of LTP/LTD in the hippocampus, separately.

Results

Prenatal exposure to methadone or DM did not affect survival rate, body weight, water maze and LTP or LTD of offspring. However, prenatal methadone significantly increased the withdrawal symptoms, pain sensitivity, addiction liability and decreased the mRNA expression of pain related opioid receptors. Co-administration of DM with methadone in the maternal rats effectively prevented these abnormalities of offspring induced by methadone.

Conclusions

Our study clearly showed that co-administration of dextromethorphan with methadone in the maternal rats prevented the adverse effects induced by prenatal methadone exposure. It implies that dextromethorphan may have a potential to be used in combination with methadone for maintenance treatment in pregnant heroin-addicted women to prevent the adverse effects induced by methadone on offspring.

Electronic supplementary material

The online version of this article (doi:10.1186/s12929-015-0126-2) contains supplementary material, which is available to authorized users.

A Multidisciplinary Approach to the Treatment of Co-occurring Opioid Use Disorder and Posttraumatic Stress Disorder in Pregnancy: A Case Report

Perinatal opioid use disorders negatively impact maternal and neonatal outcomes and are a public health problem of increasing severity. More than half of women with a substance use disorder have a history of posttraumatic stress disorder that, if not adequately addressed, can impede substance use disorder treatment. This case report describes complexities in the treatment of a pregnant woman with opioid use disorder and posttraumatic stress disorder and reviews the psychotherapeutic and pharmacologic approaches available to treat these co-occurring disorders in pregnancy. This case demonstrates the importance of early screening and intervention for co-occurring posttraumatic stress disorder in pregnant women who use substances in a closely coordinated, multidisciplinary approach to improve outcomes for women and their infants.

The opioid system and brain development: effects of methadone on the oligodendrocyte lineage and the early stages of myelination

Oligodendrocytes express opioid receptors throughout development, but the role of the opioid system in myelination remains poorly understood. This is a significant problem as opioid use and abuse continue to increase in two particular populations: pregnant addicts (in whom drug effects could target early myelination in the fetus and newborn) and adolescents and young adults (in whom late myelination of 'higher-order' regions takes place). Maintenance treatments for opioid addicts include the long-lasting opioids methadone and buprenorphine. Similar to our previous findings on the effects of buprenorphine, we have now found that early myelination in the developing rat brain is also altered by perinatal exposure to therapeutic doses of methadone. Pups exposed to this drug exhibited elevated brain levels of the 4 major splicing variants of myelin basic protein, myelin proteolipid protein, and myelin-oligodendrocyte glycoprotein. Consistent with the enrichment and function of these proteins in mature myelin, analysis of the corpus callosum in these young animals also indicated an elevated number of axons with already highly compacted myelin sheaths. Moreover, studies in cultured cells showed that methadone exerts direct effects at specific stages of the oligodendrocyte lineage, stimulating the proliferation of progenitor cells while on the other hand accelerating the maturation of the more differentiated but still immature preoligodendrocytes. While the long-term effects of these observations remain unknown, accelerated or increased oligodendrocyte maturation and myelination could both disrupt the complex sequence of synchronized events leading to normal connectivity in the developing brain. Together with our previous observations on the effects of buprenorphine, the present findings further underscore a crucial function of the endogenous opioid system in the control of oligodendrocyte development and the timing of myelination. Interference with these regulatory systems by opioid use or maintenance treatments could disrupt the normal process of brain maturation at critical stages of myelin formation.

Alternative matrices for cocaine, heroin, and methadone in utero drug exposure detection

INTRODUCTION

Drug determination in biological matrices from the mother and the newborn is an objective measure of maternal and fetal drug exposure. The aim of this study was to compare maternal hair, meconium, umbilical cord, and placenta for detecting in utero drug exposure to cocaine, opiates, methadone, and amphetamines.

METHOD

Maternal hair, meconium, umbilical cord, and placenta were collected from 175 mother-newborn dyads. Maternal hair (segmented in trimesters) and meconium specimens were analyzed for cocaine, opiates, methadone, and amphetamines. If either maternal hair or meconium tested positive, umbilical cord and placenta were analyzed. Analyses were performed by liquid chromatography tandem mass spectrometry.

RESULTS

In hair, 24 participants tested positive; 21 for cocaine [cocaine 20-50,605, benzoylecgonine (BE) 17-46,668 pg/mg], 7 for methadone (76-26,845 pg/mg), 2 for opiates (morphine 298-2398 pg/mg, codeine 65-914 pg/mg, 6-acetylmorphine 1635-15,657 pg/mg), and 1 for amphetamines (amphetamine 1990 pg/mg, 3,4-methylenedioxyamphetamine 30 pg/mg, 3,4-methylenedioxymethamphetamine 294 pg/mg). In meconium, 6 were positive; 5 for methadone [methadone 88-3752, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) 642-25,179 ng/g], 3 for cocaine (cocaine 7, BE 79, hydroxybenzoylecgonine 5-135, ecgonine-methyl ester 2-56 ng/g), and 2 for opiates (morphine 152-1025, morphine-3-glucuronide 22-23, codeine 4-34 ng/g). Placenta and umbilical cord were positive in 5 and 6 cases, respectively; 5 for methadone in placenta (methadone 7-543, EDDP 10-51 ng/g) and cord (methadone 3-183, EDDP 2-109 ng/g); 1 for cocaine in placenta (cocaine 7, BE 2 ng/g) and cord (BE 6 ng/g); and 1 for opiates in placenta (morphine 6, morphine-3-glucuronide 48 ng/g), and 2 in cord (morphine 2, morphine-3-glucuronide 15-38, morphine-6-glucuronide 5 ng/g). Meconium, placenta, and umbilical cord only tested positive if hair concentrations were greater than Society of Hair Testing cutoffs.

CONCLUSIONS

Maternal hair is the most sensitive specimen to detect drug consumption during pregnancy. Placenta and umbilical cord could be alternatives to meconium for detecting high in utero drug exposure.

Obstetric Pharmacokinetic Dosing Studies are Urgently Needed

Use of pharmacotherapy during pregnancy is common and increasing. Physiologic changes during pregnancy may significantly alter the overall systemic drug exposure, necessitating dose changes. A search of PubMed for pharmacokinetic clinical trials showed 494 publications during pregnancy out of 35,921 total pharmacokinetic published studies (1.29%), from the late 1960s through August 31, 2013. Closer examination of pharmacokinetic studies in pregnant women published since 2008 (81 studies) revealed that about a third of the trials were for treatment of acute labor and delivery issues, a third included studies of infectious disease treatment during pregnancy, and the remaining third were for varied ante-partum indications. Approximately, two-thirds of these recent studies were primarily funded by government agencies worldwide, one-quarter were supported by private non-profit foundations or combinations of government and private funding, and slightly <10% were supported by pharmaceutical industry. As highlighted in this review, vast gaps exist in pharmacology information and evidence for appropriate dosing of medications in pregnant women. This lack of knowledge and understanding of drug disposition throughout pregnancy place both the mother and the fetus at risk for avoidable therapeutic misadventures - suboptimal efficacy or excess toxicity - with medication use in pregnancy. Increased efforts to perform and support obstetric dosing and pharmacokinetic studies are greatly needed.

Fetal assessment before and after dosing with buprenorphine or methadone

AIM

To determine pre- and post-dosing effects of prenatal methadone compared to buprenorphine on fetal wellbeing.

DESIGN

A secondary analysis of data derived from the Maternal Opioid Treatment: Human Experimental Research (MOTHER) study, a double-blind, double-dummy, randomized clinical trial.

SETTING

Six United States sites and one European site that provided comprehensive opioid-dependence treatment to pregnant women.

PARTICIPANTS

Eighty-one of the 131 opioid-dependent pregnant women completing the MOTHER clinical trial, assessed between 31 and 33 weeks of gestation.

MEASUREMENTS

Two fetal assessments were conducted, once before and once after study medication dosing. Measures included mean fetal heart rate (FHR), number of FHR accelerations, FHR reactivity in the fetal non-stress test (NST) and biophysical profile (BPP) score.

FINDINGS

Significant group differences were found for number of FHR accelerations, non-reactive NST and BPP scores (all Ps < 0.05). There were no significant group differences before time of dosing. Significant decreases (all Ps < 0.05) occurred from pre- to post-dose assessment for mean FHR, FHR accelerations, reactive NST and fetal movement. The decrease in accelerations and reactive NST were significant only for fetuses in the methadone group, and this resulted in a significantly lower likelihood of a reactive NST compared to fetuses in the buprenorphine group.

CONCLUSION

Buprenorphine compared with methadone appears to result in less suppression of mean fetal heart rate, fetal heart rate reactivity and the biophysical profile score after medication dosing and these findings provide support for the relative safety of buprenorphine when fetal indices are considered as part of the complete risk-benefit ratio.

Methadone and metabolites in hair of methadone-assisted pregnant women and their infants

INTRODUCTION

Methadone is the recommended pharmacotherapy for opioid-dependent pregnant women. The primary aims of this study were to determine whether a dose-concentration relationship exists between cumulative maternal methadone dose, methadone and metabolite concentrations in maternal hair during pregnancy and whether maternal hair methadone and metabolite concentrations predict neonatal outcomes.

MATERIALS AND METHODS

Hair specimens were collected monthly from opioid-dependent mothers enrolled in methadone treatment and 4 of their infants. Hair specimens were segmented (3 cm), washed (maternal hair only), and analyzed for methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), and 2-ethyl-5-methyl-3,3-diphenylpyrroline by liquid chromatography tandem mass spectrometry.

RESULTS

There was large intersubject variability and no dose-concentration relationship for cumulative methadone dose and methadone, EDDP, 2-ethyl-5-methyl-3,3-diphenylpyrroline, or total concentrations in hair. For individual women, a positive trend was noted for cumulative methadone dose and methadone and EDDP concentrations in hair. There was a positive linear trend for cumulative methadone dose and EDDP/methadone ratio in maternal hair, perhaps reflecting methadone's induction of its own metabolism. Maternal methadone concentrations were higher than those in infant hair, and infant EDDP hair concentrations were higher than those in maternal hair. Maternal methadone dose, and methadone and EDDP hair concentrations were not correlated with peak infant neonatal abstinence syndrome (NAS) scores, days to peak NAS, duration of NAS, time to NAS onset, birth length, head circumference, or amount of neonatal morphine pharmacotherapy. Maternal cumulative third trimester methadone dose was positively correlated with infant birth weight.

CONCLUSIONS

Methadone and EDDP in pregnant women's hair are markers of methadone exposure and do not predict total methadone dose, nor neonatal outcomes from in utero methadone exposure.

Cocaine and its metabolites in the placenta: a systematic review of the literature

It is clear that cocaine and cocaine metabolites are present in the placenta and may harm the fetus. The results of the experimental manipulation of cocaine exposure are not reported in the literature in a consistent manner. We conducted a systematic review of selected articles that demonstrated the analytical detection of cocaine and its metabolites in the placenta and that were published from January 1, 1956-June 30, 2011 using Medline, Toxline and Scopus databases. The collected data confirm that the placenta does not act as a barrier to fetal exposure, that cocaine quickly crosses the placenta and that one of the essential roles of the placenta is to metabolize cocaine during pregnancy. Our systematic review summarized the results showing that cocaine, benzoylecgonine and norcocaine are stored in the myometrium and the placental membrane and maintain continuous drug delivery to the amniotic fluid (and to the fetus) probably via diffusion.

Preliminary buprenorphine sublingual tablet pharmacokinetic data in plasma, oral fluid, and sweat during treatment of opioid-dependent pregnant women

BACKGROUND

Buprenorphine is currently under investigation as a pharmacotherapy to treat pregnant women for opioid dependence. This research evaluates buprenorphine (BUP), norbuprenophine (NBUP), buprenorphine-glucuronide (BUP-Gluc), and norbuprenorphine-glucuronide (NBUP-Gluc) pharmacokinetics after high-dose (14-20 mg) BUP sublingual tablet administration in three opioid-dependent pregnant women.

METHODS

Oral fluid and sweat specimens were collected in addition to plasma specimens for 24 hours during gestation weeks 28 or 29 and 34, and 2 months after delivery. Time to maximum concentration was not affected by pregnancy; however, BUP and NBUP maximum concentration and area under the curve at 0 to 24 hours tended to be lower during pregnancy compared with postpartum levels.

RESULTS

Statistically significant but weak positive correlations were found for BUP plasma and OF concentrations and BUP/NBUP ratios in plasma and oral fluid. Statistically significant negative correlations were observed for times of specimen collection and BUP and NBUP oral fluid/plasma ratios. BUP-Gluc and NBUP-Gluc were detected in only 5% of oral fluid specimens. In sweat, BUP and NBUP were detected in only four of 25 (12 or 24 hours) specimens in low concentrations (less than 2.4 ng/patch).

CONCLUSION

These preliminary data describe BUP and metabolite pharmacokinetics in pregnant women and suggest that, like methadone, upward dose adjustments may be needed with advancing gestation.