Bidirectional transfer of methadone across human placenta

Effects of prenatal opioid exposure on infant sympathetic and parasympathetic nervous system activity

Prenatal opioid exposure has been associated with developmental problems, including autonomic nervous system dysregulation. However, little is known about the effects of prenatal opioid exposure on the autonomic nervous system beyond the first days of life, particularly across both the parasympathetic and sympathetic branches, and when accounting for exposure to other substances. The present study examined the effects of prenatal exposure to opioid agonist therapy (OAT, e.g., methadone) and other opioids on infant autonomic nervous system activity at rest and in response to a social stressor (the Still-Face Paradigm) at six months among 86 infants varying in prenatal opioid and other substance exposure. Results indicated that OAT and other opioids have unique effects on the developing autonomic nervous system that may further depend on subtype (i.e., methadone versus buprenorphine) and timing in gestation. Results are discussed in the context of theoretical models of the developing stress response system.

Methadone administered to rat dams during pregnancy and lactation affects the circadian rhythms of their pups

The circadian clock is one of the most important homeostatic systems regulating the majority of physiological functions. Its proper development contributes significantly to the maintenance of health in adulthood. Methadone is recommended for the treatment of opioid use disorders during pregnancy, increasing the number of children prenatally exposed to long-acting opioids. Although early-life opioid exposure has been studied for a number of behavioral and physiological changes observed later in life, information on the relationship between the effects of methadone exposure and circadian system development is lacking. Using a rat model, we investigated the effects of prenatal and early postnatal methadone administration on the maturation of the circadian clockwork in the suprachiasmatic nucleus (SCN) and liver, the rhythm of aralkylamine N-acetyltransferase (AA-NAT) activity in the pineal gland, and gene expression in the livers of 20-day-old rats. Our data show that repeated administration of methadone to pregnant and lactating mothers has significant effect on rhythmic gene expression in the SCN and livers and on the rhythm of AA-NAT in the offspring. Similar to previous studies with morphine, the rhythm amplitudes of the clock genes in the SCN and liver were unchanged or enhanced. However, six of seven specific genes in the liver showed significant downregulation of their expression, compared to the controls in at least one experimental group. Importantly, the amplitude of the AA-NAT rhythm was significantly reduced in all methadone-treated groups. As there is a strong correlation with melatonin levels, this result could be of importance for clinical practice.

In utero methadone exposure permanently alters anatomical and functional connectivity: A preclinical evaluation

The opioid epidemic is an ongoing public health crisis, and children born following prenatal opioid exposure (POE) have increased risk of long-term cognitive and behavioral sequelae. Clinical studies have identified reduced gray matter volume and abnormal white matter microstructure in children with POE but impacts on whole-brain functional brain connectivity (FC) have not been reported. To define effects of POE on whole brain FC and white matter injury in adult animals, we performed quantitative whole-brain structural and functional MRI. We used an established rat model of POE in which we have previously reported impaired executive function in adult rats analogous to persistent neurocognitive symptoms described in humans with POE. Pregnant Sprague-Dawley rat dams received continuous methadone (12 mg/kg/day) vs. saline infusion for 28 days via osmotic mini-pumps, exposing rats to pre- and postnatal opioid until weaning. At young adult age (P60), POE and saline exposed offspring underwent in vivo MRI included diffusion tensor imaging and functional MRI (fMRI). Results indicate that fractional anisotropy (FA) was decreased in adult animals with POE [n = 11] compared to animals that received saline [n = 9] in major white matter tracts, including the corpus callosum (p < 0.001) and external capsule (p < 0.01). This change in FA was concomitant with reduced axial diffusivity in the external capsule (p < 0.01) and increased radial diffusivity in the corpus callosum (p < 0.01). fMRI analyses reveal brainwide FC was diffusely lower in POE (p < 10^-6; 10% of variance explained by group). Decreased connectivity in cortical-cortical and cortico-basal ganglia circuitry was particularly prominent with large effect sizes (Glass's Δ > 1). Taken together, these data confirm POE reduces brainwide functional connectivity as well as microstructural integrity of major white matter tracts. Altered neural circuitry, dysregulated network refinement, and diffuse network dysfunction have been implicated in executive function deficits that are common in children with POE. FC may serve as a translatable biomarker in children with POE.

Predicting Human Fetal Drug Exposure Through Maternal-Fetal PBPK Modeling and In Vitro or Ex Vivo Studies

Medication (drug) use in human pregnancy is prevalent. Determining fetal safety and efficacy of drugs is logistically challenging. However, predicting (not measuring) fetal drug exposure (systemic and tissue) throughout pregnancy is possible through maternal-fetal physiologically based pharmacokinetic (PBPK) modeling and simulation. Such prediction can inform fetal drug safety and efficacy. Fetal drug exposure can be quantified in 2 complementary ways. First, the ratio of the steady-state unbound plasma concentration in the fetal plasma (or area under the plasma concentration-time curve) to the corresponding maternal plasma concentration (ie, Kp,uu ). Second, the maximum unbound peak (Cu,max,ss,f ) and trough (Cu,min,ss,f ) fetal steady-state plasma concentrations. We (and others) have developed a maternal-fetal PBPK model that can successfully predict maternal drug exposure. To predict fetal drug exposure, the model needs to be populated with drug specific parameters, of which transplacental clearances (active and/or passive) and placental/fetal metabolism of the drug are critical. Herein, we describe in vitro studies in cells/tissue fractions or the perfused human placenta that can be used to determine these drug-specific parameters. In addition, we provide examples whereby this approach has successfully predicted systemic fetal exposure to drugs that passively or actively cross the placenta. Apart from maternal-fetal PBPK models, animal studies also have the potential to estimate fetal drug exposure by allometric scaling. Whether such scaling will be successful is yet to be determined. Here, we review the above approaches to predict fetal drug exposure, outline gaps in our knowledge to make such predictions and map out future research directions that could fill these gaps.

Severity of neonatal opioid withdrawal syndrome with prenatal exposure to serotonin reuptake inhibitors

OBJECTIVE

To evaluate the severity of neonatal opioid withdrawal syndrome (NOWS) in infants prenatally exposed to medications for opioid use disorder (MOUD) and serotonin reuptake inhibitors (SRI).

METHODS

A prospective cohort included 148 maternal-infant pairs categorized into MOUD (n = 127) and MOUD + SRI (n = 27) groups. NOWS severity was operationalized as the infant's need for pharmacologic treatment with opioids, duration of hospitalization, and duration of treatment. The association between prenatal SRI exposure and the need for pharmacologic treatment (logistic regression), time-to-discharge, and time-to-treatment discontinuation (Cox proportional hazards modeling) was examined after adjusting for the type of maternal MOUD, use of hydroxyzine, other opioids, benzodiazepines/sedatives, alcohol, tobacco, marijuana, gestational age, and breastfeeding.

RESULTS

Infants in the MOUD + SRI group were more likely to receive pharmacologic treatment for NOWS (OR = 3.58; 95% CI: 1.31; 9.76) and had a longer hospitalization (median: 11 vs. 6 days; HR = 0.54; 95% CI: 0.33; 0.89) compared to the MOUD group. With respect to time-to-treatment discontinuation, no association was observed in infants who received treatment (HR = 0.59; 95% CI: 0.26, 1.32); however, significant differences were observed in the entire sample (HR = 0.55; 95% CI: 0.34, 0.89).

CONCLUSIONS

Use of SRIs among pregnant women on MOUD might be associated with more severe NOWS.

IMPACT

A potential drug-drug interaction between maternal SRIs and opioid medications that inhibit the reuptake of serotonin has been hypothesized but not carefully evaluated in clinical studies. Results of this prospective cohort indicate that the use of SRIs among pregnant women on MOUD is associated with more severe neonatal opioid withdrawal syndrome. This is the first prospective study which carefully examined effect modification between the type of maternal MOUD and SRI use on neonatal outcomes. This report lays the foundation for treatment optimization in pregnant women with co-occurring mental health and substance use disorders.

Consequences of Parental Opioid Exposure on Neurophysiology, Behavior, and Health in the Next Generations

Substance abuse and the ongoing opioid epidemic represents a large societal burden. This review will consider the long-term impact of opioid exposure on future generations. Prenatal, perinatal, and preconception exposure are reviewed with discussion of both maternal and paternal influences. Opioid exposure can have long-lasting effects on reproductive function, gametogenesis, and germline epigenetic programming, which can influence embryogenesis and alter the developmental trajectory of progeny. The potential mechanisms by which preconception maternal and paternal opioid exposure produce deleterious consequences on the health, behavior, and physiology of offspring that have been identified by clinical and animal studies will be discussed. The timing, nature, dosing, and duration of prenatal opioid exposure combined with other important environmental considerations influence the extent to which these manipulations affect parents and their progeny. Epigenetic inheritance refers to the transmission of environmental insults across generations via mechanisms independent of the DNA sequence. This topic will be further explored in the context of prenatal, perinatal, and preconception opioid exposure for both the maternal and paternal lineage.

Prenatal exposure to opioids: Associations between the caregiving environment and externalizing behaviors

Maternal opioid use during pregnancy is a rapidly growing public health crisis and is associated with a range of adverse developmental outcomes including externalizing behaviors among exposed children. Recent work has highlighted the role of indirect pathways from prenatal opioid exposure to behavioral outcomes through aspects of the caregiving environment, including parenting. This review highlights maternal sensitivity and related aspects of the caregiving environment that may impact the development of externalizing behaviors among children with a history of prenatal exposure to opioids. We conclude by providing suggestions for future directions in research examining development among children with prenatal opioid exposure.

Endogenous and exogenous opioid effects on oligodendrocyte biology and developmental brain myelination

The elevated presence of opioid receptors and their ligands throughout the developing brain points to the existence of maturational functions of the endogenous opioid system that still remain poorly understood. The alarmingly increasing rates of opioid use and abuse underscore the urgent need for clear identification of those functions and the cellular bases and molecular mechanisms underlying their physiological roles under normal and pathological conditions. This review is focused on current knowledge on the direct and indirect regulatory roles that opioids may have on oligodendrocyte development and their generation of myelin, a complex insulating membrane that not only facilitates rapid impulse conduction but also participates in mechanisms of brain plasticity and adaptation. Information is examined in relation to the importance of endogenous opioid function, as well as direct and indirect effects of opioid analogues, which like methadone and buprenorphine are used in medication-assisted therapies for opioid addiction during pregnancy and pharmacotherapy in neonatal abstinence syndrome. Potential opioid effects are also discussed regarding late myelination of the brain prefrontal cortex in adolescents and young adults. Such knowledge is fundamental for the design of safer pharmacological interventions for opioid abuse, minimizing deleterious effects in the developing nervous system.

Precision dosing of methadone during pregnancy: A pharmacokinetics virtual clinical trials study

BACKGROUND

Methadone use for the management of opioid dependency during pregnancy is commonplace. Methadone levels are altered during pregnancy due to changes in maternal physiology. Despite this, a paucity of data exist regarding the most appropriate optimal dosing regimens during pregnancy.

METHODS

This study applied a pharmacokinetic modeling approach to examine gestational changes in R- and S-methadone concentrations in maternal plasma and fetal (cord) blood. This study did so to derive a theoretical optimal dosing regimen during pregnancy, and to identify the impact of Cytochromes P450 (CYP) 2B6 and 2C19 polymorphisms on methadone maternal and fetal pharmacokinetics.

RESULTS

The study noted significant decreases in maternal R- and S-methadone plasma concentrations during gestation, with concomitant increases in fetal levels. At a dose of 90 mg once daily, 75% (R-) and 94% (S-) of maternal methadone trough levels were below the lower therapeutic window at term (week 40). The developed optimal dosing regimen escalated doses to 110 mg by week 5, followed by 10 mg increments every 5 weeks up to a maximum of 180 mg once daily near term. This increase resulted in 27% (R-) and 11% (S-) of subjects with trough levels below the lower therapeutic window at term. CYP2B6 poor metabolizers (PM) and either CYP2C19 extensive metabolizers (EM), PM, or ultra-rapid (UM) metabolizer phenotypes demonstrated statistically significant increases in concentrations when compared to their matched CYP2B6 EM counterparts.

CONCLUSIONS

Specific and gestation-dependent dose titrations are required during pregnancy to reduce the risks associated with illicit drug use and to maintain fetal safety.

Prenatal opioid exposure and vulnerability to future substance use disorders in offspring

The heightened incidence of opioid use during pregnancy has resulted in unprecedented rates of neonates prenatally exposed to opioids. Prenatal opioid exposure (POE) results in significantly adverse medical, developmental, and behavioral outcomes in offspring. Of growing interest is whether POE contributes to future vulnerability to substance use disorders. The effects of POE on brain development is difficult to assess in humans, as the timing, dose, and route of drug exposure together with complex genetic and environmental factors affect susceptibility to addiction. Preclinical models of POE have allowed us to avoid methodological difficulties and confounding factors of POE in humans. Here, we review the effects of maternal opioid exposure on the developing brain with an emphasis on the neurobiological basis of drug addiction and on preclinical models of POE and their limitations. These studies have indicated that POE increases self-administration of drugs, reward-driven behaviors in the conditioned place paradigm, and locomotor sensitization. While addiction is multifaceted and vulnerability to drug addiction is still inconclusive in human studies of prenatally exposed infants, animal studies do provide a noteworthy corroboration of negative behavioral outcomes.

Opioid maintenance treatment of pregnant women in the Scandinavian countries

Background:

WHO guidelines emphasise the need for descriptions of clinical practice and observational studies on risk and benefits of pharmacotherapies in pregnancy. The aims of the present study were to: (1) Describe opioid maintenance treatment (OMT) in the Scandinavian countries in general, and specifically for pregnant women, (2) Describe a project which utilises a new approach using registry-linkage data to examine associations between prenatal exposure to OMT and child outcomes: a Scandinavian cohort study of pregnant women in OMT during pregnancy (ScopeOMT).

Data:

Guidelines describing the treatment of persons with opioid use disorders in general, and specifically for pregnant women. Scandinavian registry-linkage data from ScopeOMT.

Results:

Registry data show that approximately 800 pregnant women received OMT during pregnancy in the period of the ScopeOMT study. Similarities across the Scandinavian countries include access to free healthcare and treatment; multidisciplinary teams trained to support pregnant women in OMT; buprenorphine as the recommended drug when initiating therapy; and a holistic focus on the patients’ lives. An important difference is that Norwegian women who use illegal substances that may harm the foetus may be admitted – voluntarily, or against their will – for parts of, or the remainder of the pregnancy to inpatient treatment at specialised clinics.

Conclusion:

Many similarities in the treatment provided to opioid-dependent persons in the Scandinavian countries place this area in an excellent position to combine the efforts and carry out observational studies concerning the safety of OMT during pregnancy.

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.

Prenatal opioid exposure: The next neonatal neuroinflammatory disease

The rates of opioid use disorder during pregnancy have more than quadrupled in the last decade, resulting in numerous infants suffering exposure to opioids during the perinatal period, a critical period of central nervous system (CNS) development. Despite increasing use, the characterization and definition of the molecular and cellular mechanisms of the long-term neurodevelopmental impacts of opioid exposure commencing in utero remains incomplete. Thus, in consideration of the looming public health crisis stemming from the multitude of infants with prenatal opioid exposure entering school age, we undertook an investigation of the effects of perinatal methadone exposure in a novel preclinical model. Specifically, we examined the effects of opioids on the developing brain to elucidate mechanisms of putative neural cell injury, to identify diagnostic biomarkers and to guide clinical studies of outcome and follow-up. We hypothesized that methadone would induce a pronounced inflammatory profile in both dams and their pups, and be associated with immune system dysfunction, sustained CNS injury, and altered cognition and executive function into adulthood. This investigation was conducted using a combination of cellular, molecular, biochemical, and clinically translatable biomarker, imaging and cognitive assessment platforms. Data reveal that perinatal methadone exposure increases inflammatory cytokines in the neonatal peripheral circulation, and reprograms and primes the immune system through sustained peripheral immune hyperreactivity. In the brain, perinatal methadone exposure not only increases chemokines and cytokines throughout a crucial developmental period, but also alters microglia morphology consistent with activation, and upregulates TLR4 and MyD88 mRNA. This increase in neuroinflammation coincides with reduced myelin basic protein and altered neurofilament expression, as well as reduced structural coherence and significantly decreased fractional anisotropy on diffusion tensor imaging. In addition to this microstructural brain injury, adult rats exposed to methadone in the perinatal period have significant impairment in associative learning and executive control as assessed using touchscreen technology. Collectively, these data reveal a distinct systemic and neuroinflammatory signature associated with prenatal methadone exposure, suggestive of an altered CNS microenvironment, dysregulated developmental homeostasis, complex concurrent neural injury, and imaging and cognitive findings consistent with clinical literature. Further investigation is required to define appropriate therapies targeted at the neural injury and improve the long-term outcomes for this exceedingly vulnerable patient population.

Educational achievement at age 9.5 years of children born to mothers maintained on methadone during pregnancy

Recent research shows that preschool children born to opioid-dependent mothers are at increased risk for cognitive, psychomotor, attention, and social-emotional adjustment problems. But very little is known about their school-age functioning, particularly their educational achievement. This analysis examined the educational outcomes of a regional cohort of 100 prenatally methadone-exposed children who were prospectively studied from birth to age 9.5 years alongside a comparison group of 110 randomly identified non-exposed children born between 2003 and 2008. At age 9.5, as part of a comprehensive neurodevelopmental evaluation, children's teachers rated their achievement across the school curriculum, and children completed the Woodcock Johnson-III Tests of Achievement (WJ-III). Detailed information about the birth mother's social background, pregnancy substance use, and mental health was also collected during pregnancy/at term. Infant clinical data were collected after birth. Methadone-exposed children performed less well than non-exposed children across seven school curriculum areas rated by teachers (ps ≤.001), performed less well than non-exposed children on all reading and mathematics subtests of the WJ-III, and had higher rates of any educational delay on the WJ-III (57% vs. 15%), OR = 7.47 (3.71-15.02). Results were similar when children with severe intellectual impairment were excluded. After adjusting for confounding factors, methadone-exposed children had increased odds of educational delay, but this was only marginally significant (OR = 3.62, [1.01-13.01], p = .049). Maternal educational attainment level (OR = 0.69, [0.50-0.89], p = .006), and maternal benzodiazepine use during pregnancy (OR = 2.70 [1.03-7.12], p = .044) were also associated with later educational risk. Findings suggest that children born to opioid-dependent women enrolled in methadone maintenance are at high risk of educational delay by age 9.5 years. Children's academic difficulties appeared to reflect the effects of both adverse prenatal exposures and postnatal social risk.

Salivary cortisol levels relate to cognitive performance in children prenatally exposed to methadone or buprenorphine

Opioid maintenance therapy (OMT) is generally recommended for pregnant opioid-dependent women. However, much is still unknown about the potential long-term effects of prenatal methadone and buprenorphine exposure. This study explored the long-term effects of prenatal methadone and buprenorphine exposure in a cohort (n = 41) of children, aged 9-11 years, using the Wechsler Abbreviated Scale of Intelligence (WASI) to measure cognitive development and salivary cortisol samples to measure HPA-axis activity. Prenatally exposed children scored significantly lower on all four subtests of WASI (vocabulary, similarities, block design, and matrix reasoning), compared to a comparison group (all p < .05). No group differences were found for salivary cortisol levels or cortisol reactivity levels (all p > .05). Cortisol levels significantly predicted matrix reasoning scores for the OMT group, β = -65.58, t(20) = 15.70, p = .02. Findings suggest that prenatal exposure to methadone or buprenorphine does not have long-term effects on children's HPA-axis functioning. However, since children of women in OMT scored significantly lower on tasks of cognitive function, careful follow-up throughout the school years and across adolescence is recommended.

High Accumulation of Methadone Compared with Buprenorphine in Fetal Rat Brain after Maternal Exposure

Experimental animal studies are valuable in revealing a causal relationship between prenatal exposure to opioid maintenance treatment (OMT) and subsequent effects; however, previous animal studies of OMT during pregnancy have been criticized for their lack of clinical relevance because of their use of high drug doses and the absence of pharmacokinetic data. Hence, the aim of this study was to determine blood and brain concentrations in rat dams, fetuses, and offspring after continuous maternal exposure to methadone or buprenorphine during gestation and to examine the offspring for neonatal outcomes and withdrawal symptoms. Female rats were implanted with a 28-day osmotic minipump delivering methadone (10 mg/kg per day), buprenorphine (1 mg/kg per day) or vehicle 5 days before mating. Continuous exposure to methadone or buprenorphine induced stable blood concentrations in the dams of 0.25 ± 0.02 µM and 5.65 ± 0.16 nM, respectively. The fetal brain concentration of methadone (1.89 ± 0.35 nmol/g) was twice as high as that in the maternal brain, whereas the fetal brain concentration of buprenorphine (20.02 ± 4.97 pmol/g) was one-third the maternal brain concentration. The opioids remained in the offspring brain several days after the exposure ceased. Offspring prenatally exposed to methadone, but not buprenorphine, displayed reduced body weight and length and increased corticosterone levels. No significant changes in ultrasonic vocalizations were revealed. Our data in rat fetuses and neonates indicate that OMT with buprenorphine may be a better choice than methadone during pregnancy. SIGNIFICANCE STATEMENT: Concern has been raised about the use of opioid maintenance treatment during pregnancy because of the important role of the endogenous opioid system in brain development. Here, we show that the methadone concentration in the fetal rat brain was twice as high as that in the maternal brain, whereas the buprenorphine concentration was one-third the maternal concentration. Furthermore, buprenorphine allowed more favorable birth outcomes, suggesting that buprenorphine may be a better choice during pregnancy.

ERP correlates of cognitive control in children prenatally exposed to methadone or buprenorphine

Much is still unknown about the potential long-term effects of prenatal methadone and buprenorphine exposure. We examined neural correlates of cognitive control in 19 prenatally methadone and buprenorphine exposed and 21 nondrug exposed children, aged 9-11 years. Children performed a modified version of the Eriksen Flanker task, which taps into selective attention, conflict response, and response inhibition mechanisms. We investigated behavioral responses and the ERP components N1, P2, N2, P3, and the late positive component (LPC). Children in the exposed group showed normal cognitive control function. However, an atypical ERP response related to perceptual and attention allocation processes was found in the exposed group.

Brain morphology in school-aged children with prenatal opioid exposure: A structural MRI study

BACKGROUND

Both animal and human studies have suggested that prenatal opioid exposure may be detrimental to the developing fetal brain. However, results are somewhat conflicting. Structural brain changes in children with prenatal opioid exposure have been reported in a few studies, and such changes may contribute to neuropsychological impairments observed in exposed children.

AIM

To investigate the association between prenatal opioid exposure and brain morphology in school-aged children.

STUDY DESIGN

A cross-sectional magnetic resonance imaging (MRI) study of prenatally opioid-exposed children and matched controls.

SUBJECTS

A hospital-based sample (n=16) of children aged 10-14years with prenatal exposure to opioids and 1:1 sex- and age-matched unexposed controls.

OUTCOME MEASURES

Automated brain volume measures obtained from T1-weighted MRI scans using FreeSurfer.

RESULTS

Volumes of the basal ganglia, thalamus, and cerebellar white matter were reduced in the opioid-exposed group, whereas there were no statistically significant differences in global brain measures (total brain, cerebral cortex, and cerebral white matter volumes).

CONCLUSIONS

In line with the limited findings reported in the literature to date, our study showed an association between prenatal opioid exposure and reduced regional brain volumes. Adverse effects of opioids on the developing fetal brain may explain this association. However, further research is needed to explore the causal nature and functional consequences of these findings.

Opiate Drugs with Abuse Liability Hijack the Endogenous Opioid System to Disrupt Neuronal and Glial Maturation in the Central Nervous System

The endogenous opioid system, comprised of multiple opioid neuropeptide and receptor gene families, is highly expressed by developing neural cells and can significantly influence neuronal and glial maturation. In many central nervous system (CNS) regions, the expression of opioid peptides and receptors occurs only transiently during development, effectively disappearing with subsequent maturation only to reemerge under pathologic conditions, such as with inflammation or injury. Opiate drugs with abuse liability act to modify growth and development by mimicking the actions of endogenous opioids. Although typically mediated by μ-opioid receptors, opiate drugs can also act through δ- and κ-opioid receptors to modulate growth in a cell-type, region-specific, and developmentally regulated manner. Opioids act as biological response modifiers and their actions are highly contextual, plastic, modifiable, and influenced by other physiological processes or pathophysiological conditions, such as neuro-acquired immunodeficiency syndrome. To date, most studies have considered the acute effects of opiates on cellular maturation. For example, activating opioid receptors typically results in acute growth inhibition in both neurons and glia. However, with sustained opioid exposure, compensatory factors become operative, a concept that has been largely overlooked during CNS maturation. Accordingly, this article surveys prior studies on the effects of opiates on CNS maturation, and also suggests new directions for future research in this area. Identifying the cellular and molecular mechanisms underlying the adaptive responses to chronic opiate exposure (e.g., tolerance) during maturation is crucial toward understanding the consequences of perinatal opiate exposure on the CNS.

Placental ABC Transporters: Biological Impact and Pharmaceutical Significance

The human placenta fulfills a variety of essential functions during prenatal life. Several ABC transporters are expressed in the human placenta, where they play a role in the transport of endogenous compounds and may protect the fetus from exogenous compounds such as therapeutic agents, drugs of abuse, and other xenobiotics. To date, considerable progress has been made toward understanding ABC transporters in the placenta. Recent studies on the expression and functional activities are discussed. This review discusses the placental expression and functional roles of several members of ABC transporter subfamilies B, C, and G including MDR1/P-glycoprotein, the MRPs, and BCRP, respectively. Since placental ABC transporters modulate fetal exposure to various compounds, an understanding of their functional and regulatory mechanisms will lead to more optimal medication use when necessary in pregnancy.

Bidirectional Transfer Study of Polystyrene Nanoparticles across the Placental Barrier in an ex Vivo Human Placental Perfusion Model

BACKGROUND

Nanoparticle exposure in utero might not be a major concern yet, but it could become more important with the increasing application of nanomaterials in consumer and medical products. Several epidemiologic and in vitro studies have shown that nanoparticles can have potential toxic effects. However, nanoparticles also offer the opportunity to develop new therapeutic strategies to treat specifically either the pregnant mother or the fetus. Previous studies mainly addressed whether nanoparticles are able to cross the placental barrier. However, the transport mechanisms underlying nanoparticle translocation across the placenta are still unknown.

OBJECTIVES

In this study we examined which transport mechanisms underlie the placental transfer of nanoparticles.

METHODS

We used the ex vivo human placental perfusion model to analyze the bidirectional transfer of plain and carboxylate modified polystyrene particles in a size range between 50 and 300 nm.

RESULTS

We observed that the transport of polystyrene particles in the fetal to maternal direction was significantly higher than for the maternal to fetal direction. Regardless of their ability to cross the placental barrier and the direction of perfusion, all polystyrene particles accumulated in the syncytiotrophoblast of the placental tissue.

CONCLUSIONS

Our results indicate that the syncytiotrophoblast is the key player in regulating nanoparticle transport across the human placenta. The main mechanism underlying this translocation is not based on passive diffusion, but is likely to involve an active, energy-dependent transport pathway. These findings will be important for reproductive toxicology as well as for pharmaceutical engineering of new drug carriers.

Transporter-Mediated Disposition of Opioids: Implications for Clinical Drug Interactions

Opioid-related deaths, abuse, and drug interactions are growing epidemic problems that have medical, social, and economic implications. Drug transporters play a major role in the disposition of many drugs, including opioids; hence they can modulate their pharmacokinetics, pharmacodynamics and their associated drug-drug interactions (DDIs). Our understanding of the interaction of transporters with many therapeutic agents is improving; however, investigating such interactions with opioids is progressing relatively slowly despite the alarming number of opioids-mediated DDIs that may be related to transporters. This review presents a comprehensive report of the current literature relating to opioids and their drug transporter interactions. Additionally, it highlights the emergence of transporters that are yet to be fully identified but may play prominent roles in the disposition of opioids, the growing interest in transporter genomics for opioids, and the potential implications of opioid-drug transporter interactions for cancer treatments. A better understanding of drug transporters interactions with opioids will provide greater insight into potential clinical DDIs and could help improve opioids safety and efficacy.

A systematic review of the cardiotoxicity of methadone

Methadone is one of the most popular synthetic opioids in the world with some favorable properties making it useful both in the treatment of moderate to severe pain and for opioid addiction. Increased use of methadone has resulted in an increased prevalence of its toxicity, one aspect of which is cardiotoxicity. In this paper, we review the effects of methadone on the heart as well as cardiac concerns in some special situations such as pregnancy and childhood.

METHODS

We searched for the terms methadone, toxicity, poisoning, cardiotoxicity, heart, dysrhythmia, arrhythmia, QT interval prolongation, torsade de pointes, and Electrocardiogram (ECG) in bibliographical databases including TUMS digital library, PubMed, Scopus, and Google Scholar. This review includes relevant articles published between 2000 and 2013. The main cardiac effects of methadone include prolongation of QT interval and torsade de pointes. Other effects include changes in QT dispersion, pathological U waves, Taku-Tsubo syndrome (stress cardiomyopathy), Brugada-like syndrome, and coronary artery diseases. The aim of this paper is to inform physicians and health care staff about these adverse effects. Effectiveness of methadone in the treatment of pain and addiction should be weighed against these adverse effects and physicians should consider the ways to lessen such undesirable effects. This article presents some recommendations to prevent heart toxicity in methadone users.

UHPLC-MS/MS quantification of buprenorphine, norbuprenorphine, methadone, and glucuronide conjugates in umbilical cord plasma

Opioid use during pregnancy can result in the newborn being physically dependent on the substance, thus experiencing drug withdrawal, termed neonatal abstinence syndrome (NAS). Buprenorphine and methadone are two drugs used to treat opioid withdrawal and are approved for use in pregnancy. Quantification of these compounds in umbilical cord plasma would help assess in utero exposure of neonates in cases of buprenorphine or methadone use during pregnancy. An LC-MS/MS method using solid-phase extraction sample preparation was developed and validated for the simultaneous quantification of methadone, buprenorphine, norbuprenorphine, and glucuronide metabolites in umbilical cord plasma. The average accuracy (percentage error) and precision (relative standard deviation) were <15% for each validated concentration. Our data establishes a 2 week maximum freezer storage window in order to achieve the most accurate cord plasma concentrations of these analytes. Additionally, we found that the umbilical cord tissue analysis was less sensitive compared with analysis with umbilical cord blood plasma, indicating that this may be a more appropriate matrix for determination of buprenorphine and metabolite concentrations. This method was successfully applied to the analysis of cord blood from women with known buprenorphine or methadone use during pregnancy.

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.

Mid-Gestational Enlargement of Fetal Thalami in Women Exposed to Methadone during Pregnancy

Methadone maintenance therapy is the standard of care in many countries for opioid-dependent women who become pregnant. Despite recent evidence showing significant neurodevelopmental changes in children and adults exposed to both licit and illicit substances in utero, data on the effects of opioids in particular remains scarce. The purpose of this study was to examine the effects of opiate use, in particular methadone, on various fetal cortical and biometric growth parameters in utero using ultrasound measurements done at 18-22 weeks gestation. Head circumference (HC), bi-parietal diameter, lateral ventricle diameter, transcerebellar diameter, thalamic diameter, cisterna magna diameter, and femur length were compared between fetuses born to methadone-maintained mothers and non-substance using controls. A significantly larger thalamic diameter (0.05 cm, p = 0.01) was observed in the opiate-exposed group. Thalamic diameter/HC ratio was also significantly raised (0.03 mm, p = 0.01). We hypothesize here that the increase in thalamic diameter in opiate-exposed fetuses could potentially be explained by regional differences in opioid and serotonin receptor densities, an alteration in monoamine neurotransmitter systems, and an enhancement of the normal growth increase that occurs in the thalamus during mid-gestation.

Highlights in opioid agonists and antagonists

This review highlights new insights in to opioid agonists and antagonists, focusing on their mechanism of action with spinal and systemic administration, chronic use and main adverse effects. Short-cuts on some opioid agonists and antagonists of clinical interest are also presented, revealing potential clinical implications and future clinical directions as part of multimodal analgesia.

Deviant smooth pursuit in preschool children exposed prenatally to methadone or buprenorphine and tobacco affects integrative visuomotor capabilities

BACKGROUND AND AIMS

Although an increasing number of children are born to mothers in opioid maintenance therapy (OMT), little is known about the long-term effects of these opioids. Previous studies suggest an association between prenatal OMT exposure and difficulties in eye movement control. Also, the effects of tobacco smoking on eye movements have been reported. The present study examined the influence of eye movements, i.e. smooth pursuit, on visuomotor capabilities in children of smoking mothers in OMT.

DESIGN

The study comprised a 2 (OMT versus contrast group) × 2 (slow versus fast smooth pursuit) between-subject factorial design.

SETTING

The cognitive developmental research unit at the University of Oslo, Norway.

PARTICIPANTS

Participants were 26 4-year-old children of tobacco-smoking women in OMT and 23 non-exposed 4-year-old children, with non-smoking mothers, matched by gender and age.

MEASUREMENT

Eye movements and smooth pursuit were recorded using a Tobii 1750 eyetracker. Visuomotor functions were examined by Bender test.

FINDINGS

The OMT group tracked slowly moving objects with smooth pursuit in a similar manner to their non-exposed peers. When fast smooth pursuit was measured, the OMT group of children tracked the object more slowly than the contrast group, P = 0.02, ηp(2) = 0.11. A regression analysis showed that fast smooth pursuit predicted children's performance on a visuomotor task, R(2) = 0.37.

CONCLUSION

Impaired eye-tracking skills in 4-year-old children exposed to methadone or buprenorphine and tobacco prenatally could inhibit the development of some cognitive functions in later life.

Development of auditory event-related potentials in infants prenatally exposed to methadone

Developmental features of the P2 auditory ERP in a change detection paradigm were examined in infants prenatally exposed to methadone. Opiate dependent pregnant women maintained on methadone replacement therapy were recruited during pregnancy (N = 60). Current and historical alcohol and substance use, SES, and psychiatric status were assessed with a maternal interview during the third trimester. Medical records were used to collect information regarding maternal medications, monthly urinalysis, and breathalyzer to confirm comorbid drug and alcohol exposures. Between birth and 4 months infant ERP change detection performance was evaluated on one occasion with the oddball paradigm (.2 probability oddball) using pure-tone stimuli (standard = 1 kHz and oddball = 2 kHz frequency) at midline electrode sites, Fz, Cz, Pz. Infant groups were examined in the following developmental windows: 4-15, 16-32, or 33-120 days PNA. Older groups showed increased P2 amplitude at Fz and effective change detection performance at P2 not seen in the newborn group. Developmental maturation of amplitude and stimulus discrimination for P2 has been reported in developing infants at all of the ages tested and data reported here in the older infants are consistent with typical development. However, it has been previously reported that the P2 amplitude difference is detectable in neonates; therefore, absence of a difference in P2 amplitude between stimuli in the 4-15 days group may represent impaired ERP performance by neonatal abstinence syndrome or prenatal methadone exposure.

Opioid addiction in pregnancy

The purpose of this review is to discuss the incidence, risks, pregnancy complications, and maintenance options for treatment of opioid addiction in pregnancy.

SUMMARY

Opioid dependence in pregnancy carries clear identifiable maternal and fetal risk. Providing care for patients with dependence is best done in a multidisciplinary care model addressing the particular needs of this population. There are limited data on maternal detoxification, with data still emerging surrounding the safety profile of this practice. Historically, methadone has been the recommended maintenance treatment; however, recent data on buprenorphine identify this as a safe and effective option. The majority of births from women with opioid dependence result in neonatal abstinence syndrome requiring prolonged neonatal hospitalization. Intrapartum pain management should not differ from the general obstetric population. Postpartum pain is magnified in this population, and particular attention should be focused on this issue. Breast-feeding is recommended regardless of maintenance dose, unless other conditions restricting breast-feeding are present. Comprehensive postpartum care and transition of care to addiction specialists are highly recommended.

TARGET AUDIENCE

Obstetricians and gynecologists, family physicians, addiction specialists.

LEARNING OBJECTIVES

After completing this CME activity, physicians should be better able to assess the treatment options available to patients with opioid addiction during pregnancy, compare the risk/safety profiles of methadone and buprenorphine, and evaluate the recommendations and current data surrounding breast-feeding while on opioid maintenance treatment.

Differences in the profile of neonatal abstinence syndrome signs in methadone- versus buprenorphine-exposed neonates

AIMS

To compare the profile of signs of neonatal abstinence syndrome (NAS) in methadone- versus buprenorphine-exposed infants.

DESIGN, SETTING AND PARTICIPANTS

Secondary analysis of NAS data from a multi-site, double-blind, double-dummy, flexible-dosing, randomized clinical trial. Data from a total of 129 neonates born to opioid-dependent women who had been assigned to receive methadone or buprenorphine treatment during pregnancy were examined.

MEASUREMENTS

For 10 days after delivery, neonates (methadone = 72, buprenorphine = 57) were assessed regularly using a 19-item modified Finnegan scale. Data from neonates who required pharmacological treatment (methadone = 41, buprenorphine = 27) were included up to the time treatment was initiated. The incidence and mean severity of the total NAS score and each individual sign of NAS were calculated and compared between medication conditions, as was the median time until morphine treatment initiation among treated infants in each condition.

FINDINGS

Two NAS signs (undisturbed tremors and hyperactive Moro reflex) were observed significantly more frequently in methadone-exposed neonates and three (nasal stuffiness, sneezing, loose stools) were observed more frequently in buprenorphine-exposed neonates. Mean severity scores on the total NAS score and five individual signs (disturbed and undisturbed tremors, hyperactive Moro reflex, excessive irritability, failure to thrive) were significantly higher among methadone-exposed neonates, while sneezing was higher among buprenorphine-exposed neonates. Among treated neonates, methadone-exposed infants required treatment significantly earlier than buprenorphine-exposed infants (36 versus 59 hours postnatal, respectively).

CONCLUSIONS

The profile of neonatal abstinence syndrome differs in methadone- versus buprenorphine-exposed neonates, with significant differences in incidence, severity and treatment initiation time. Overall, methadone-exposed neonates have a more severe neonatal abstinence syndrome.

Transplacental transfer of vancomycin and telavancin

OBJECTIVE

We sought to determine the bidirectional transfer and distribution of vancomycin and telavancin across the dually perfused term human placental lobule.

STUDY DESIGN

The technique of dually perfused placental lobule was used in its recirculating mode to determine the maternal to fetal (M→F) (n = 20) and fetal to maternal (n = 18) transfer of each antibiotic, which were coperfused with their radioactive isotopes. The concentrations of drugs were determined by liquid scintillation spectrometry.

RESULTS

In the M→F direction, the transfer of vancomycin (9.6 ± 4%) and telavancin (6.5 ± 2%) were low; however, telavancin retention by the perfused lobule was greater than that of vancomycin (P < .01). The normalized transplacental transfer of telavancin across the placental lobule in the fetal to maternal direction was higher than in the M→F direction (P < .01), suggesting the involvement of placental efflux transporters.

CONCLUSION

The ex vivo perfusion experiments revealed low transfer of vancomycin and telavancin to the fetal circuit.

Pharmacotherapy in pregnancy; effect of ABC and SLC transporters on drug transport across the placenta and fetal drug exposure

Pharmacotherapy during pregnancy is often inevitable for medical treatment of the mother, the fetus or both. The knowledge of drug transport across placenta is, therefore, an important topic to bear in mind when deciding treatment in pregnant women. Several drug transporters of the ABC and SLC families have been discovered in the placenta, such as P-glycoprotein, breast cancer resistance protein, or organic anion/cation transporters. It is thus evident that the passage of drugs across the placenta can no longer be predicted simply on the basis of their physical-chemical properties. Functional expression of placental drug transporters in the trophoblast and the possibility of drug-drug interactions must be considered to optimize pharmacotherapy during pregnancy. In this review we summarize current knowledge on the expression and function of ABC and SLC transporters in the trophoblast. Furthermore, we put this data into context with medical conditions that require maternal and/or fetal treatment during pregnancy, such as gestational diabetes, HIV infection, fetal arrhythmias and epilepsy. Proper understanding of the role of placental transporters should be of great interest not only to clinicians but also to pharmaceutical industry for future drug design and development to control the degree of fetal exposure.

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.

Effects of rifampicin, dexamethasone, St. John's Wort and Thyroxine on maternal and foetal expression of Abcb1 and organ distribution of talinolol in pregnant rats

It is well accepted that ABCB1 plays a critical role in absorption, distribution and elimination of many xenobiotics and drugs. Only little is known about the regulation and function of ABCB1 during pregnancy. Thus, the aim of this study is to investigate maternal, placental and foetal Abcb1 expression and function in pregnant rats after induction with rifampicin, dexamethasone, St. John's wort (SJW) or thyroxine. Wistar rats were orally treated with rifampicin (250 mg/kg), SJW (1.0 g/kg), thyroxine (9 μg/kg), dexamethasone (1 mg/kg) or 0.5% methylcellulose suspension (control) for 9 days during late pregnancy (each N = 5). Afterwards, organ mRNA expression and protein content of Abcb1a were determined. Tissue concentrations of the ABCB1 probe drug talinolol were measured after repeated administration of the drug (100 mg/kg, 9 days) and after induction with oral rifampicin (250 mg/kg, 9 days, N = 5). Abcb1 expression was substantially lower in foetal than in maternal organs. Abcb1 was significantly induced by SJW in the maternal jejunum and placenta, by dexamethasone in foetal brain and liver and by thyroxine in the placenta and maternal and foetal brain. Rifampicin induced Abcb1 in all maternal and foetal organs. However, organ distribution of talinolol was not influenced by comedication of rifampicin. In conclusion, maternal and foetal Abcb1 organ expression in pregnant rats is inducible by nuclear receptor agonists. Although rifampicin regulates maternal and foetal Abcb1 expression, organ distribution of talinolol remains unchanged most likely caused by the known inhibitory effect of rifampicin on Abcb1 function.

Opioid dependency in pregnancy and length of stay for neonatal abstinence syndrome

OBJECTIVE

To examine opioid replacement therapy in pregnancy and effect on neonatal outcomes, including length of hospital stay for neonatal abstinence syndrome.

DESIGN

Retrospective descriptive study.

SETTING

Labor and delivery unit and neonatal intensive care unit (NICU), Eastern Maine Medical Center, Bangor, Maine.

PARTICIPANTS

One hundred fifty-two opioid-dependent pregnant women on methadone maintenance therapy (MMT) (n = 136) or buprenorphine maintenance therapy (BMT) (n = 16) during pregnancy and their neonates. The neonates were born between January 1, 2005 and December 31, 2007.

METHODS

A review of the electronic medical record (EMR) was conducted of all opioid-dependent women who were maintained on MMT or BMT at the time of admission for labor and delivery and their neonates.

RESULTS

Maternal methadone dose and concomitant in-utero exposure to benzodiazepines prolonged the length of hospital stay for neonates. Length of stay was shorter in breastfed neonates than formula-fed neonates or neonates who received formula and breast milk. Neonates with prenatal exposure to MMT spent more days in the hospital (21 vs. 14 days) for treatment of neonatal abstinence syndrome (NAS) than infants with prenatal exposure to BMT.

CONCLUSION

These findings are consistent with previous research on the simultaneous use of methadone and benzodiazepines during pregnancy and provide further direction for the treatment of opioid dependency during pregnancy. Harm reduction strategies for opioid-dependent pregnant women in substance abuse treatment with MMT may one day include guidance on daily treatment doses and recommendations to avoid the concomitant use of benzodiazepines to lessen NAS. Breastfeeding should be recommended to shorten length of stay. Understanding perinatal and neonatal outcomes of pregnant women on methadone or buprenorphine will help to identify optimal treatment for opioid dependency in pregnancy.

Methadone, cocaine, opiates, and metabolite disposition in umbilical cord and correlations to maternal methadone dose and neonatal outcomes

OBJECTIVES

The purpose was to explore methadone and 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) umbilical cord disposition, correlate with maternal methadone dose and neonatal outcomes, and evaluate the window of drug detection in umbilical cord of in utero illicit drug exposure.

METHODS

Subjects comprised 19 opioid-dependent pregnant women from 2 clinical studies, one comparing methadone and buprenorphine pharmacotherapy for opioid-dependence treatment and the second examining monetary reinforcement schedules to maintain drug abstinence. Correlations were calculated for methadone and EDDP umbilical cord concentrations and maternal methadone dose, and neonatal outcomes. Cocaine- and opiate-positive umbilical cord concentrations were compared with those in placenta and meconium, and urine specimens collected throughout gestation.

RESULTS

Significant positive correlations were found for umbilical cord methadone concentrations and methadone mean daily dose, mean dose during the third trimester, and methadone cumulative daily dose. Umbilical cord EDDP concentrations and EDDP/methadone concentration ratios were positively correlated to newborn length, peak neonatal abstinence syndrome (NAS) score, and time-to-peak NAS score. Methadone concentrations and EDDP/methadone ratios in umbilical cord and placenta were positively correlated. Meconium identified many more cocaine- and opiate-positive specimens than did umbilical cord.

CONCLUSIONS

Umbilical cord methadone concentrations were correlated to methadone doses. Also, our results indicate that methadone and EDDP concentrations might help to predict the NAS severity. Meconium proved to be more suitable than umbilical cord to detect in utero exposure to cocaine and opiates; however, umbilical cord could be useful when meconium is unavailable due to in utero or delayed expulsion.

Prenatal exposure to methadone and buprenorphine: a review of the potential effects on cognitive development

The amount of opioid users receiving opioid maintenance therapy has increased significantly over the last few years. As a result, an increasing number of children are prenatally exposed to long-lasting opioids such as methadone and buprenorphine. This article reviews the literature on the cognitive development of children born to mothers in opioid maintenance therapy. Topics discussed are the effects of prenatal exposure on prematurity, somatic growth, brain volume, myelination, and the endocrine and neurotransmitter system. Social-environmental factors, including parental functioning, as well as genetic factors are also described. Areas requiring further research are identified.

(R)- and (S)-methadone and buprenorphine concentration ratios in maternal and umbilical cord plasma following chronic maintenance dosing in pregnancy

AIMS

The aim of this study was to compare the transfer of buprenorphine and methadone between maternal and cord blood in women under chronic dosing conditions and to determine if differences exist in the transfer of the two methadone enantiomers.

METHODS

Maternal and cord blood samples were collected at delivery from women maintained on methadone (35, 25-140 mg day⁻¹) (median; range) or buprenorphine (6.00, 2-20 mg day⁻¹) during pregnancy. Plasma concentration ratios are presented as an indicator of foetal exposure relative to the mother.

RESULTS

Methadone was quantified in all samples, with cord : maternal plasma methadone concentration ratios (n= 15 mother-infant pairs) being significantly higher (P < 0.0001; mean difference (MD) 0.07; 95% confidence interval (CI) 0.048, 0.092) for the active (R)-methadone enantiomer (0.41; 0.19, 0.56) (median; range) compared with (S)-methadone (0.36; 0.15, 0.53). (R)- : (S)-methadone concentration ratios were also significantly higher (P < 0.0001; MD 0.24 95% CI 0.300, 0.180) for cord (1.40; 0.95, 1.67) compared with maternal plasma (1.16; 0.81, 1.38). Half the infant buprenorphine samples were below the assay lower limit of quantification (LLOQ) (0.125 ng ml⁻¹). The latter was four-fold lower than the LLOQ for methadone (0.50 ng ml⁻¹). The cord : maternal plasma buprenorphine concentration ratio (n= 9 mother-infant pairs) was 0.35; 0.14, 0.47 and for norbuprenorphine 0.49; 0.24, 0.91.

CONCLUSIONS

The transfer of the individual methadone enantiomers to the foetal circulation is stereoselective. Infants born to buprenorphine maintained women are not exposed to a greater proportion of the maternal dose compared with methadone and may be exposed to relatively less of the maternal dose compared with infants born to women maintained on methadone during pregnancy.

Maternal methadone dose, placental methadone concentrations, and neonatal outcomes

BACKGROUND

Few investigations have used placenta as an alternative matrix to detect in utero drug exposure, despite its availability at the time of birth and the large amount of sample. Methadone-maintained opioid-dependent pregnant women provide a unique opportunity to examine the placental disposition of methadone and metabolite [2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP)], to explore their correlations with maternal methadone dose and neonatal outcomes, and to test the ability to detect in utero exposure to illicit drugs.

METHODS

We calculated the correlations of placental methadone and EDDP concentrations and their correlations with maternal methadone doses and neonatal outcomes. Cocaine- and opiate-positive placenta results were compared with the results for meconium samples and for urine samples collected throughout gestation.

RESULTS

Positive correlations were found between placental methadone and EDDP concentrations (r=0.685), and between methadone concentration and methadone dose at delivery (r=0.542), mean daily dose (r=0.554), mean third-trimester dose (r=0.591), and cumulative daily dose (r=0.639). The EDDP/methadone concentration ratio was negatively correlated with cumulative daily dose (r=-0.541) and positively correlated with peak neonatal abstinence syndrome (NAS) score (r=0.513). Placental EDDP concentration was negatively correlated with newborn head circumference (r=-0.579). Cocaine and opiate use was detected in far fewer placenta samples than in thrice-weekly urine and meconium samples, a result suggesting a short detection window for placenta.

CONCLUSIONS

Quantitative methadone and EDDP measurement may predict NAS severity. The placenta reflects in utero drug exposure for a shorter time than meconium but may be useful when meconium is unavailable or if documentation of recent exposure is needed.

Prenatal methadone exposure, meconium biomarker concentrations and neonatal abstinence syndrome

AIMS

Methadone is standard pharmacotherapy for opioid-dependent pregnant women, yet the relationship between maternal methadone dose and neonatal abstinence syndrome (NAS) severity is still unclear. This research evaluated whether quantification of fetal methadone and drug exposure via meconium would reflect maternal dose and predict neonatal outcomes.

DESIGN

Prospective clinical study.

SETTING

An urban drug treatment facility treating pregnant and post-partum women and their children.

PARTICIPANTS

Forty-nine opioid-dependent pregnant women received 30-110 mg methadone daily.

MEASUREMENTS

Maternal methadone dose, infant birth parameters and NAS assessments were extracted from medical records. Thrice-weekly urine specimens were screened for opioids and cocaine. Newborn meconium specimens were quantified for methadone, opioid, cocaine and tobacco biomarkers.

FINDINGS

There was no relationship between meconium methadone concentrations, presence of opioids, cocaine and/or tobacco in meconium, maternal methadone dose or NAS severity. Opioid and cocaine were also found in 36.7 and 38.8 of meconium specimens, respectively, and were associated with positive urine specimens in the third trimester. The presence of opioids other than methadone in meconium correlated with increased rates of preterm birth, longer infant hospital stays and decreased maternal time in drug treatment.

CONCLUSIONS

Methadone and its metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) concentrations in meconium did not predict infant birth parameters or NAS severity. Prospective urine testing defined meconium drug detection windows for opiates and cocaine as 3 months, rather than the currently accepted 6 months. The presence of opioids in meconium could be used as a biomarker for infants at elevated risk in the newborn period.

Relationship between maternal methadone dose at delivery and neonatal abstinence syndrome

OBJECTIVE

To estimate the relationship between maternal methadone dose and the incidence of neonatal abstinence syndrome (NAS).

STUDY DESIGN

We performed a retrospective cohort study of pregnant women treated with methadone for opiate addiction who delivered live-born neonates between 1996 and 2006. Four dose groups, on the basis of total daily methadone dose, were compared (<or=80 mg/d, 81-120 mg/d, 121-160 mg/d, and >160 mg/d). The primary outcome was treatment for NAS. Symptoms of NAS were objectively measured with the Finnegan scoring system, and treatment was initiated for a score>24 during the prior 24 hours.

RESULTS

A total of 330 women treated with methadone and their 388 offspring were included. Average methadone dose at delivery was 117+/-50 mg/d (range, 20-340 mg/d). Overall, 68% of infants were treated for NAS. Of infants exposed to methadone doses<or=80 mg/d, 81-120 mg/d, 121-160 mg/d, and >160 mg/d, treatment for NAS was initiated for 68%, 63%, 70%, and 73% of neonates, respectively (P=.48). The rate of maternal illicit opiate abuse at delivery was 26%, 28%, 19%, and 11%, respectively (P=.04).

CONCLUSION

No correlation was found between maternal methadone dose and rate of NAS. However, higher doses of methadone were associated with decreased illicit opiate abuse at delivery.

Expression and function of p-glycoprotein in normal tissues: effect on pharmacokinetics

ATP-binding cassette (ABC) drug efflux transporters limit intracellular concentration of their substrates by pumping them out of cell through an active, energy dependent mechanism. Several of these proteins have been originally associated with the phenomenon of multidrug resistance; however, later on, they have also been shown to control body disposition of their substrates. P-glycoprotein (Pgp) is the first detected and the best characterized of ABC drug efflux transporters. Apart from tumor cells, its constitutive expression has been reported in a variety of other tissues, such as the intestine, brain, liver, placenta, kidney, and others. Being located on the apical site of the plasma membrane, Pgp can remove a variety of structurally unrelated compounds, including clinically relevant drugs, their metabolites, and conjugates from cells. Driven by energy from ATP, it affects many pharmacokinetic events such as intestinal absorption, brain penetration, transplacental passage, and hepatobiliary excretion of drugs and their metabolites. It is widely believed that Pgp, together with other ABC drug efflux transporters, plays a crucial role in the host detoxication and protection against xenobiotic substances. On the other hand, the presence of these transporters in normal tissues may prevent pharmacotherapeutic agents from reaching their site of action, thus limiting their therapeutic potential. This chapter focuses on P-glycoprotein, its expression, localization, and function in nontumor tissues and the pharmacological consequences hereof.

Opiates inhibit paclitaxel uptake by P-glycoprotein in preparations of human placental inside-out vesicles

The use of either methadone or buprenorphine for treatment of the pregnant opiate-dependent patient improves maternal and neonatal outcome. However, patient outcomes are often complicated by neonatal abstinence syndrome (NAS). The incidence and severity of NAS should depend on opiate concentration in the fetal circulation. Efflux transporters expressed in human placental brush border membranes decrease fetal exposure to medications by their extrusion to the maternal circulation. Accordingly, the concentration of either methadone or buprenorphine in the fetal circulation is, in part, dependent on the activity of the efflux transporters. The objective of this study was to characterize the activity of P-gp and its interaction with opiates in the placental apical membrane. Therefore, brush border membrane vesicles were prepared from human placenta. The vesicles were oriented approximately 75% inside-out, exhibited saturable ATP-dependent uptake of P-gp substrate [(3)H]-paclitaxel with an apparent K(t) of 66+/-38 nM and V(max) of 20+/-3 pmol mg protein (-1)min(-1). Methadone, buprenorphine, and morphine inhibited paclitaxel transport with apparent K(i) of 18, 44, and 90 microM, respectively. Our data indicate that a method has been established to determine the activity of the efflux transporter P-gp, expressed in placental brush border membranes, and the kinetics for the transfer of its prototypic substrate paclitaxel. Furthermore, the method was used to determine the effects of methadone, buprenorphine, and morphine on paclitaxel transfer by placental P-gp and revealed that they have higher affinity to the transporter than its classical inhibitor verapamil (K(i), 300 microM).