Dose-adjusted plasma concentrations of sublingual buprenorphine are lower during than after pregnancy

Mechanisms of altered hepatic drug disposition during pregnancy: small molecules

INTRODUCTION

Pregnancy alters the systemic exposure and clearance of many hepatically cleared drugs that are commonly used by obstetric patients. Understanding the molecular mechanisms underlying the changes in factors that affect hepatic drug clearance (blood flow, protein binding, and intrinsic clearance) is essential to more precisely predict systemic drug exposure and dose requirements in obstetric patients.

AREAS COVERED

This review (1) summarizes the anatomic, physiologic, and biochemical changes in maternal hepatic, cardiovascular, endocrine, and renal systems relevant to hepatic drug clearance and (2) reviews the molecular mechanisms underlying the altered hepatic metabolism and intrinsic clearance of drugs during pregnancy via a comprehensive PubMed search. It also identifies knowledge gaps in the molecular mechanisms and factors that modulate hepatic drug clearance during pregnancy.

EXPERT OPINION

Pharmacokinetic studies have shown that pregnancy alters systemic exposure, protein binding, and clearance of many drugs during gestation in part due to pregnancy-associated decreases in plasma albumin, increases in organ blood flow, and changes in the activity of drug-metabolizing enzymes (DMEs) and transporters. The changes in the activity of certain DMEs and transporters during pregnancy are likely driven by hormonal-changes that inhibit their activity or alter the expression of these proteins through activation of transcription factors.

A Pharmacologic Evaluation of Buprenorphine in Pregnancy and the Postpartum Period

BACKGROUND

The dosing regimen in the package insert for sublingual buprenorphine is similar for pregnant and nonpregnant people despite the physiologic changes seen during pregnancy.

AIMS

To compare plasma buprenorphine pharmacokinetics during and after pregnancy and relate buprenorphine concentration to the pharmacodynamic endpoints of pupil diameter, Clinical Opioid Withdrawal Scale (COWS), and craving scores.

STUDY DESIGN

Prospective cohort of 22 pregnant people undergoing 33 pharmacologic studies (6-8 hours each) during pregnancy or postpartum. Participants were on a stable daily dose of 2-8 mg sublingual buprenorphine every 6 or 8 hours. The dosing frequency was selected by the participant. On study day, baseline measurements of plasma buprenorphine, pupil diameter, COWS, and craving scores were obtained, then the usual morning dose was taken, and measurements were repeated several times over 1 dosing interval.

FINDINGS

The dose-normalized area under the plasma buprenorphine concentration time curve was significantly ( P = 0.036) lower during pregnancy (155 ± 52 ng × min/mL) than postpartum (218 ± 113 ng × min/mL). Buprenorphine trough concentrations were similar at the start (1.1 ± 0.7 ng/mL) and end of a dosing cycle (1.2 ± 0.8 ng/mL) regardless of dosing frequency. Pupillary diameter, COWS, and craving scores returned to baseline as buprenorphine concentrations approached ~1 ng/mL.

CONCLUSIONS

Pregnant people require a higher dose of buprenorphine to achieve concentrations comparable to nonpregnant people. There is a temporal relationship between the plasma buprenorphine concentration and the pharmacodynamic markers of pupillary diameter, COWS, and craving scores. An average plasma concentration of ~1 ng/mL was associated with the lowest level of COWS and craving scores.

An Approach for Improving the Detection and Quantitation of Buprenorphine and Its Metabolites in Maternal and Neonatal Hair

BACKGROUND

Buprenorphine (BUP) use is prevalent in pregnant women with opioid use disorder (OUD). Drug monitoring during pregnancy is critical for optimizing dosing regimen and achieving the desired clinical outcomes. Hair can be used as a critical biological matrix for monitoring long-term exposure to drugs. The aim of this study was to optimize the methodology used to quantify BUP and its metabolites in hair samples.

METHODS

Conditions for hair sample processing (ie, hair washing, incubation temperature, and extraction time) were optimized to maximize extraction recovery. The LC-MS/MS strategy employed here used 4 deuterated internal standards for quantifying BUP and its major metabolites [norbuprenorphine (NBUP), buprenorphine glucuronide (BUP-G), and norbuprenorphine-glucuronide (NBUP-G)] in human hair samples. The optimized conditions were used to measure BUP and its metabolites in hair samples of 5 women undergoing OUD treatment and their neonates.

RESULTS

Unwashed hair samples processed by shaking with acetonitrile for 24 hours at 37 °C showed higher BUP (36%) and NBUP (67%) recovery, compared with those processed by incubation at room temperature. The standard curves showed excellent linearity over 0.05-100 ng/mL for BUP and NBUP and 0.1-200 ng/mL for BUP-G and NBUP-G. The assay was partially validated for reproducibility and accuracy and was successfully used for measuring BUP and metabolites in aforementioned hair samples. BUP was identified in all hair samples, while BUP-G was not. BUP was the primary analyte in maternal hair (median: 38.3 pg/mg; 25-75 percentile: 17-152.4 pg/mg), while NBUP-G was predominant in neonatal hair (median: 28.6 pg/mg; 25%-75% percentile: 1.9-112.8 pg/mg).

CONCLUSIONS

The methodology used for quantifying BUP and its metabolites in hair samples of maternal female patients and their neonates is simple, accurate, and reproducible. The developed method may be useful for measuring fetal exposure to BUP during gestation.

Association between buprenorphine dose and outcomes among pregnant persons with opioid use disorder

BACKGROUND

Opioid use disorder contributes to maternal morbidity and mortality in the United States. Little is known about how the patterns of buprenorphine dose and duration throughout pregnancy may affect neonatal and postpartum outcomes.

OBJECTIVE

To determine the associations between trajectories of buprenorphine utilization and dose during pregnancy on maternal and neonatal health outcomes.

STUDY DESIGN

Retrospective cohort study among 2925 pregnant persons with opioid use disorder, followed from the estimated start date of pregnancy through 90 days after delivery. We used administrative healthcare data from Medicaid-enrolled individuals to assess buprenorphine dose and use and maternal (postpartum buprenorphine continuation and overdose) and neonatal (low birthweight, neonatal abstinence syndrome (NAS)) outcomes. Group-based trajectory modelling was used to identify trajectories of buprenorphine dose and use during pregnancy. Weighted multivariable logistic regression assessed the association between buprenorphine trajectories and outcomes.

RESULTS

We identified 8 trajectories of buprenorphine utilization and dose during pregnancy. Regression analyses found that high doses of buprenorphine and a longer duration of buprenorphine use during pregnancy was associated with higher odds of postpartum buprenorphine continuation and reduced rates of overdose. Higher doses and longer duration of buprenorphine treatment were not associated with an increase in NAS or term low birth weight, relative to moderate or low doses or shorter treatment duration.

CONCLUSION

A longer duration and higher dose of buprenorphine treatment during pregnancy were associated with improved odds of postpartum buprenorphine continuation and were not associated with adverse neonatal outcomes.

Consensus Statement on Pain Management for Pregnant Patients with Opioid-Use Disorder from the Society for Obstetric Anesthesia and Perinatology, Society for Maternal-Fetal Medicine, and American Society of Regional Anesthesia and Pain Medicine

Pain management in pregnant and postpartum people with an opioid-use disorder (OUD) requires a balance between risks associated with opioid tolerance, including withdrawal or return to opioid use, considerations around social needs of the maternal-infant dyad, and the provision of adequate pain relief for the birth episode that is often characterized as the worst pain a person will experience in their lifetime. This multidisciplinary consensus statement between the Society for Obstetric Anesthesia and Perinatology (SOAP), Society for Maternal-Fetal Medicine (SMFM), and American Society of Regional Anesthesia and Pain Medicine (ASRA) provides a framework for pain management in obstetric patients with OUD. The purpose of this consensus statement is to provide practical and evidence-based recommendations and is targeted to health care providers in obstetrics and anesthesiology. The statement is focused on prenatal optimization of pain management, labor analgesia, and postvaginal delivery pain management, and postcesarean delivery pain management. Topics include a discussion of nonpharmacologic and pharmacologic options for pain management, medication management for OUD (eg, buprenorphine, methadone), considerations regarding urine drug testing, and other social aspects of care for maternal-infant dyads, as well as a review of current practices. The authors provide evidence-based recommendations to optimize pain management while reducing risks and complications associated with OUD in the peripartum period. Ultimately, this multidisciplinary consensus statement provides practical and concise clinical guidance to optimize pain management for people with OUD in the context of pregnancy to improve maternal and perinatal outcomes.

Salivary Therapeutic Monitoring of Buprenorphine in Neonates After Maternal Sublingual Dosing Guided by Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Opioid use disorder (OUD) during pregnancy is associated with high mortality rates and neonatal opioid withdrawal syndrome (NOWS). Buprenorphine, an opioid, is used to treat OUD and NOWS. Buprenorphine active metabolite (norbuprenorphine) can cross the placenta and cause neonatal respiratory depression (EC 50 = 35 ng/mL) at high brain extracellular fluid (bECF) levels. Neonatal therapeutic drug monitoring using saliva decreases the likelihood of distress and infections associated with frequent blood sampling.

METHODS

An adult physiologically based pharmacokinetic model for buprenorphine and norbuprenorphine after intravenous and sublingual administration was constructed, vetted, and scaled to newborn and pregnant populations. The pregnancy model predicted that buprenorphine and norbuprenorphine doses would be transplacentally transferred to the newborns. The newborn physiologically based pharmacokinetic model was used to estimate the buprenorphine and norbuprenorphine levels in newborn plasma, bECF, and saliva after these doses.

RESULTS

After maternal sublingual administration of buprenorphine (4 mg/d), the estimated plasma concentrations of buprenorphine and norbuprenorphine in newborns exceeded the toxicity thresholds for 8 and 24 hours, respectively. However, the norbuprenorphine bECF levels were lower than the respiratory depression threshold. Furthermore, the salivary buprenorphine threshold levels in newborns for buprenorphine analgesia, norbuprenorphine analgesia, and norbuprenorphine hypoventilation were observed to be 22, 2, and 162 ng/mL.

CONCLUSIONS

Using neonatal saliva for buprenorphine therapeutic drug monitoring can facilitate newborn safety during the maternal treatment of OUD using sublingual buprenorphine. Nevertheless, the suitability of using adult values of respiratory depression EC 50 for newborns must be confirmed.

Simplified processing and rapid quantification of buprenorphine, norbuprenorphine, and their conjugated metabolites in human plasma using UPLC-MS/MS: Assessment of buprenorphine exposure during opioid use disorder treatment

Opioid use disorder (OUD) is a chronic neurobehavioral ailment and is prevalent in pregnancy. OUD is commonly treated with methadone or buprenorphine (BUP). Pregnancy is known to alter the pharmacokinetics of drugs and may lead to changes in drug exposure and response. A simple, specific, and sensitive analytical method for measuring the parent drug and its metabolites is valuable for assessing the impact of pregnancy on drug exposure. A new liquid chromatography-tandem mass spectrometric method that utilized a simple protein precipitation procedure for sample preparation and four deuterated internal standards for quantification was developed and validated for BUP and its major metabolites (norbuprenorphine [NBUP], buprenorphine-glucuronide [BUP-G], and norbuprenorphine-glucuronide [NBUP-G]) in human plasma. The standard curve was linear over the concentration range of 0.05-100 ng/mL for BUP and NBUP, and 0.1-200 ng/mL for BUP-G and NBUP-G. Intra- and inter-day bias and precision were within ±15% of nominal values for all the analytes. Quality controls assessed at four levels showed high recovery consistently for all the analytes with minimal matrix effect. Adequate analyte stability was observed at various laboratory conditions tested. Overall, the developed method is simple, sensitive, accurate and reproducible, and was successfully applied for the quantification of BUP and its metabolites in plasma samples collected from pregnant women in a clinical study assessing BUP exposure during OUD treatment.

Forecasting Fetal Buprenorphine Exposure through Maternal-Fetal Physiologically Based Pharmacokinetic Modeling

Buprenorphine readily crosses the placenta, and with greater prenatal exposure, neonatal opioid withdrawal syndrome (NOWS) likely grows more severe. Current dosing strategies can be further improved by tailoring doses to expected NOWS severity. To allow the conceptualization of fetal buprenorphine exposure, a maternal-fetal physiologically based pharmacokinetic (PBPK) model for sublingual buprenorphine was developed using Simcyp (v21.0). Buprenorphine transplacental passage was predicted from its physicochemical properties. The maternal-fetal PBPK model integrated reduced transmucosal absorption driven by lower salivary pH and induced metabolism observed during pregnancy. Maternal pharmacokinetics was adequately predicted in the second trimester, third trimester, and postpartum period, with the simulated area under the curve from 0 to 12 h, apparent clearance, and peak concentration falling within the 1.25-fold prediction error range. Following post hoc adjustment of the likely degree of individual maternal sublingual absorption, umbilical cord blood concentrations at delivery (n = 21) were adequately predicted, with a geometric mean ratio between predicted and observed fetal concentrations of 1.15 and with 95.2% falling within the 2-fold prediction error range. The maternal-fetal PBPK model developed in this study can be used to forecast fetal buprenorphine exposure and would be valuable to investigate its correlation to NOWS severity.

The Psychiatrist's Role in Treating Perinatal Opioid Use Disorder and Reducing Maternal Mortality

Drug overdose is a leading cause of maternal mortality. Psychiatrists can play a critical role in reducing these deaths by delivering effective evidence-based treatments for perinatal opioid use disorder (POUD), including the use of buprenorphine. Medications for POUD (i.e., buprenorphine, methadone) are life-saving treatments, but only half of those who are diagnosed as having POUD will receive this treatment, which can result in an increased risk for return to opioid use, overdose, and death. Psychiatrists are well positioned to prescribe buprenorphine given the Drug Enforcement Administration's (DEA) removal of the requirement to submit a Notice of Intent to prescribe buprenorphine for the treatment of opioid use disorders. Psychiatrists who have a current DEA registration that includes Schedule III authority may now prescribe buprenorphine for opioid use disorders; the training requirements to do so are outlined herein. This article reviews the standard of care for screening, diagnosis, and treatment of POUD, and prescribing buprenorphine for POUD, as well as shared decision-making for medication selection, induction, and maintenance of buprenorphine during pregnancy, labor and delivery, and the postpartum year.

What to Expect With Pregnant or Postpartum Prescribing of Extended-Release Buprenorphine (CAM2038)

Weekly and monthly CAM2038 (Brixadi®) extended-release subcutaneous buprenorphine (XR bup) has been available in Europe and Australia for several years and was approved by the Food and Drug Administration in May 2023. Little is known about the clinical experience of patients and providers using this new medication during prenatal care. Two cases of pregnant persons with opioid use disorder receiving weekly XR bup in an ongoing randomized multi-site outpatient clinical trial are presented along with a brief review of the pharmacology and literature on XR bup formulations. The cases in pregnancy illustrate how treatment with the weekly formulation is initiated including how to make dose adjustments, which may be necessary given the longer half-life; it takes 1 month to achieve steady state. Injection site pain with medication administration was time limited and managed readily. Other injection site reactions experienced included subcutaneous erythema and induration that was delayed in onset and typically mild, resolving with minimal intervention. Delivery management and breastfeeding recommendations while on weekly XR bup were not different compared to sublingual buprenorphine (SL bup). Weekly XR bup is a new treatment for opioid use disorder that may be used in the obstetric population. Obstetric and addiction medicine clinicians should be aware of this new formulation as its use is expected to increase.

Perinatal morphine but not buprenorphine affects gestational and offspring neurobehavioral outcomes in mice

Within the national opioid epidemic, there has been an increase in the number of infants exposed to opioids in utero. Additionally, opioid agonist medications are the standard of care for women with opioid use disorder during pregnancy. Buprenorphine (BUP), a partial µ -opioid receptor agonist, has been successful in improving gestational and neonatal outcomes. However, in utero exposure has been linked to childhood cognitive and behavioral problems. Therefore, we sought to compare offspring cognitive and behavioral outcomes after prenatal exposure to a clinically relevant low dose of BUP compared to morphine (MO), a full µ -opioid receptor agonist and immediate metabolite of heroin. We used a mouse model to assess gestational and offspring outcomes. Mouse dams were injected once daily s.c. with saline (SAL, n = 12), MO (10 mg/kg, n = 15), or BUP (0.1 mg/kg, n = 16) throughout pre-gestation, gestation, and lactation until offspring were weaned on postnatal day (P)21. Offspring social interaction and exploratory behavior were assessed, along with executive function via the touchscreen 5 choice serial reaction time task (5CSRTT). We then quantified P1 brain gene expression in the frontal cortex and amygdala (AMG). Perinatal MO but not BUP exposure decreased gestational weight gain and was associated with dystocia. In adolescent offspring, perinatal MO but not BUP exposure increased social exploration in males and grooming behavior in females. In the 5CSRTT, male MO exposed offspring exhibited increased impulsive action errors compared to male BUP offspring. In the AMG of P1 MO exposed offspring, we observed an increase in gene expression of targets related to activity of microglia. Importantly, both MO and BUP caused acute hyperlocomotion in the dams to a similar degree, indicating that the selected doses are comparable, in accordance with previous dose comparisons on analgesic and reward efficacy. These data suggest that compared to MO, low dose BUP improves gestational outcomes and has less of an effect on the neonatal offspring brain and later adolescent and adult behavior.

Accelerated Fentanyl Metabolism During Pregnancy and Impact on Prenatal Drug Testing

OBJECTIVE

To evaluate the metabolic pattern of illicit fentanyl in a sample of pregnant patients with opioid use disorder. Fentanyl pharmacokinetics during pregnancy are currently understudied yet the interpretation of a fentanyl immunoassay during pregnancy has significant implications on maternal legal custody and child welfare. Through this medical-legal lens, we demonstrate the utility of an emerging metric, the metabolic ratio, for accurate analysis of fentanyl pharmacokinetics during pregnancy.

METHODS

We conducted a retrospective cohort analysis using the electronic medical records of 420 patients receiving integrated prenatal and opioid use disorder care at a large urban safety net hospital. Data related to maternal health and substance use were collected for each subject. The metabolic ratio was calculated for each subject to measure their rate of metabolism. The sample's (n = 112) metabolic ratios were compared with a large non-pregnant sample (n = 4366).

RESULTS

The metabolic ratios of our pregnant sample were significantly (p = .0001) higher than the metabolic ratios of our non-pregnant sample, indicating that the rate of conversion to the major metabolite was faster in pregnant people. The effect size for this difference between the pregnant and non-pregnant sample was large (d = 0.86).

CONCLUSIONS FOR PRACTICE

Our findings characterize the unique metabolic pattern of fentanyl in pregnant people who use opioids, providing guidance for institutional policies around fentanyl drug testing. Additionally, our study warns of misinterpretation of toxicology results and stresses the importance of physician advocacy on behalf of pregnant women who use illicit opioids.

ASAM Clinical Considerations: Buprenorphine Treatment of Opioid Use Disorder for Individuals Using High-potency Synthetic Opioids

ABSTRACT

Treatment of opioid use disorder (OUD) with buprenorphine has evolved considerably in the last decade as the scale of the OUD epidemic has increased along with the emergence of high-potency synthetic opioids (HPSOs) and stimulants in the drug supply. These changes have outpaced the development of prospective research, so a clinical consideration document based on expert consensus is needed to address pressing clinical questions. This clinical considerations document is based on a narrative literature review and expert consensus and will specifically address considerations for changes to the clinical practice of treatment of OUD with buprenorphine for individuals using HPSO. An expert panel developed 6 key questions addressing buprenorphine initiation, stabilization, and long-term treatment for individuals with OUD exposed to HPSO in various treatment settings. Broadly, the clinical considerations suggest that individualized strategies for buprenorphine initiation may be needed. The experience of opioid withdrawal negatively impacts the success of buprenorphine treatment, and attention to its management before and during buprenorphine initiation should be proactively addressed. Buprenorphine dose and dosing frequency should be individualized based on patients' treatment needs, the possibility of novel components in the drug supply should be considered during OUD treatment, and all forms of opioid agonist treatment should be offered and considered for patients. Together, these clinical considerations attempt to be responsive to the challenges and opportunities experienced by frontline clinicians using buprenorphine for the treatment of OUD in patients using HPSOs and highlight areas where prospective research is urgently needed.

An Examination of the Complex Pharmacological Properties of the Non-Selective Opioid Modulator Buprenorphine

The goal of this review is to provide a recent examination of the pharmacodynamics as well as pharmacokinetics, misuse potential, toxicology, and prenatal consequences of buprenorphine. Buprenorphine is currently a Schedule III opioid in the US used for opioid-use disorder (OUD) and as an analgesic. Buprenorphine has high affinity for the mu-opioid receptor (MOR), delta (DOR), and kappa (KOR) and intermediate affinity for the nociceptin (NOR). Buprenorphine's active metabolite, norbuprenorphine, crosses the blood-brain barrier, is a potent metabolite that attenuates the analgesic effects of buprenorphine due to binding to NOR, and is responsible for the respiratory depressant effects. The area under the concentration curves are very similar for buprenorphine and norbuprenorphine, which indicates that it is important to consider this metabolite. Crowding sourcing has identified a buprenorphine street value (USD 3.95/mg), indicating some non-medical use. There have also been eleven-thousand reports involving buprenorphine and minors (age < 19) at US poison control centers. Prenatal exposure to clinically relevant dosages in rats produces reductions in myelin and increases in depression-like behavior. In conclusion, the pharmacology of this OUD pharmacotherapy including the consequences of prenatal buprenorphine exposure in humans and experimental animals should continue to be carefully evaluated.

Evidence on Buprenorphine Dose Limits: A Review

OBJECTIVES

As overdose deaths from fentanyl continue to increase, optimizing use of medications for opioid use disorder has become increasingly important. Buprenorphine is a highly effective medication for reducing the risk of overdose death, but only if a patient remains in treatment. Shared decision making between prescribers and patients is important to establish a dose that meets each patient's treatment needs. However, patients frequently face a dose limit of 16 or 24 mg/d based on dosing guidelines on the Food and Drug Administration's package label.

METHODS

This review discusses patient-centered goals and clinical criteria for determining dose adequacy, reviews the history of buprenorphine dose regulation in the United States, examines pharmacological and clinical research results with buprenorphine doses up to 32 mg/d, and evaluates whether diversion concerns justify maintaining a low buprenorphine dose limit.

RESULTS

Pharmacological and clinical research results consistently demonstrate buprenorphine's dose-dependent benefits up to at least 32 mg/d, including reductions in withdrawal symptoms, craving, opioid reward, and illicit use while improving retention in care. Diverted buprenorphine is most often used to treat withdrawal symptoms and reduce illicit opioid use when legal access to it is limited.

CONCLUSIONS

In light of established research and profound harms from fentanyl, the Food and Drug Administration's current recommendations on target dose and dose limit are outdated and causing harm. An update to the buprenorphine package label with recommended dosing up to 32 mg/d and elimination of the 16 mg/d target dose would improve treatment effectiveness and save lives.

Pregnancy related hormones increase CYP3A mediated buprenorphine metabolism in human hepatocytes: a comparison to CYP3A substrates nifedipine and midazolam

Introduction: Pregnancy increases the clearance of CYP3A4 substrate drugs and pregnancy-related hormones (PRHs) induce hepatic CYP3A4 expression and metabolism. However, it remains unclear to what extent the magnitude of PRH-evoked changes in hepatic CYP3A metabolism varies across multiple substrates. This study quantified the impact of PRHs on CYP3A protein concentrations and buprenorphine metabolism in human hepatocytes, and compared the magnitude of these effects to nifedipine and midazolam metabolism. Methods: Sandwich-cultured human hepatocytes (SCHH) from female donors were exposed to PRHs, administered in combination across a range of physiologically relevant concentrations, for 72 h. Absolute protein concentrations of CYP3A4, CYP3A5, and CYP3A7 in SCHH membrane fractions were quantified by nanoLC-MS/MS, and norbuprenorphine (nor-BUP), dehydro-nifedipine (dehydro-NIF), and 1-hydroxy-midazolam (1-OH-MDZ) formation was evaluated. Results: Compared to control, PRH exposure increased CYP3A4, CYP3A7, and total CYP3A protein concentrations, but not CYP3A5 concentrations, and increased nor-BUP, dehydro-NIF, and 1-OH-MDZ formation in a concentration-dependent manner. The formation of nor-BUP, dehydro-NIF, and 1-OH-MDZ each positively correlated with PRH-mediated changes in total CYP3A protein concentrations. The PRH-evoked increase in nor-BUP formation was evident in all donors; however, the PRH induction of dehydro-NIF and 1-OH-MDZ formation was diminished in a hepatocyte donor with high basal CYP3A5 expression. Discussion: These findings demonstrate that PRHs increase buprenorphine, nifedipine, and midazolam metabolism in SCHH via induction of CYP3A4 and total CYP3A protein concentrations, and the magnitude of these effects vary across hepatocyte donors in a substrate-specific manner. These data provide insight into the contribution of PRH induction of CYP3A4 metabolism to increased buprenorphine clearance during pregnancy.

Physiologic Changes During Pregnancy and Impact on Small-Molecule Drugs, Biologic (Monoclonal Antibody) Disposition, and Response

Pregnancy is a unique physiological state that results in many changes in bodily function, including cellular, metabolic, and hormonal changes. These changes can have a significant impact on the way small-molecule drugs and monoclonal antibodies (biologics) function and are metabolized, including efficacy, safety, potency, and adverse effects. In this article, we review the various physiologic changes that occur during pregnancy and their effects on drug and biologic metabolism, including changes in the coagulation, gastrointestinal, renal, endocrine, hepatic, respiratory, and cardiovascular systems. Additionally, we discuss how these changes can affect the processes of drug and biologic absorption, distribution, metabolism, and elimination (pharmacokinetics), and how drugs and biologics interact with biological systems, including mechanisms of drug action and effect (pharmacodynamics) during pregnancy, as well as the potential for drug-induced toxicity and adverse effects in the mother and developing fetus. The article also examines the implications of these changes for the use of drugs and biologics during pregnancy, including consequences of suboptimal plasma drug concentrations, effect of pregnancy on the pharmacokinetics and pharmacodynamics of biologics, and the need for careful monitoring and individualized drug dosing. Overall, this article aims to provide a comprehensive understanding of the physiologic changes during pregnancy and their effects on drug and biologic metabolism to improve the safe and effective use of drugs.

Opioids and Opioid Use Disorder in Pregnancy

Overdose is a leading cause of pregnancy-associated morbidity and mortality in the United States. As such, all obstetric providers have a responsibility to provide evidence-based care for patients with opioid use disorder to mitigate adverse outcomes associated with substance use during pregnancy.

Opioid Agonist to Buprenorphine Cross-titration During Pregnancy: A Case Report

BACKGROUND

We present a case report of a first-trimester pregnant individual with chronic pain on chronic opioid therapy who successfully cross-titrated from full-μ agonist opioid to buprenorphine without causing significant withdrawal symptoms.

CASE PRESENTATION

A 37-year-old gravida 1, para 0 woman with chronic pain on opioid therapy successfully completed a 6-week cross-titration from 120 morphine equivalent dose to buprenorphine in her first trimester without affecting pain scores, functional capacity, withdrawal symptoms except for mild nausea and insomnia, or adverse perinatal outcomes. After increasing her buprenorphine in the second trimester, at 38 weeks, she bore a healthy neonate without eliciting signs of neonatal abstinence syndrome while on a stable buprenorphine dose.

CONCLUSIONS

The American College of Obstetricians and Gynecologists and the American Society of Addiction Medicine agree that pregnant patients with chronic pain should avoid or minimize opioids. For patients on chronic opioid therapy unable to minimize opioid use during pregnancy, it is unclear whether to continue their chronic opioid therapy or transition to other medications, including buprenorphine. This case demonstrated how one pregnant person with chronic pain on opioid therapy but not meeting diagnostic criteria for opioid use disorder safely transitioned from full-μ agonist opioids to buprenorphine without precipitating withdrawal or adverse perinatal outcomes. Cross-titration could be similarly performed for a pregnant patient with untreated opioid use disorder. In addition, the used cross-titration schedule and the rationale are provided.

Inpatient Buprenorphine Induction for Opioid Use Disorder in Pregnancy

Objective Buprenorphine is a commonly used medication to manage opioid use disorder, however there is limited data to guide induction protocols specifically during pregnancy. Similar to non-pregnant patients the Clinical Opiate Withdrawal Scale (COWS) is often used to guide induction and titration of buprenorphine in pregnancy. The objective of this retrospective descriptive study is to assess the inpatient buprenorphine induction patterns, treatment retention, and pregnancy outcomes among obstetric patients with opioid use disorder seeking treatment.  Study design This was a retrospective study of obstetric patients with opioid use disorder admitted for inpatient buprenorphine induction at a large academic center between May 2015 to 2020. A descriptive analysis of the cohort, induction patterns, and dose retention after discharge were evaluated in addition to obstetric and neonatal outcomes. Results Sixty patients were admitted for inpatient buprenorphine induction at a median gestational age of 16.7 weeks. The median COWS score on presentation was 9. The starting dose for half of the patients (30 out of 60 patients) was 8 mg of buprenorphine, while 24 patients were started at 4 mg. The median duration of hospitalization was three days (range 2-12). The median buprenorphine dose upon discharge was 10 mg (range 4-20). Only 13 of the 35 patients (37%) who desired prenatal care at our institution returned to receive routine prenatal care. Of the 12 (20%) patients who delivered at our institution, nine were live births (75%). Among the live births, the median gestational age at delivery was 37.4 weeks, birth weight 3085 grams, and only one (8%) developed neonatal abstinence syndrome. Conclusion When using the Clinical Opiate Withdrawal Scale to guide inpatient buprenorphine titration for pregnant patients with opioid use disorder it takes approximately three days to establish a satisfactory maintenance dose with the median dose at discharge in this population being 10 mg. The majority of patients who followed up after hospital discharge did not need dose adjustments.

An update on the physiologic changes during pregnancy and their impact on drug pharmacokinetics and pharmacogenomics

For many years, the medical community has relied in clinical practice on historic data about the physiological changes that occur during pregnancy. However, some newer studies have disputed a number of assumptions in these data for not being evidence-based or derived from large prospective cohort-studies. Accurate knowledge of these physiological changes is important for three reasons: Firstly, it facilitates correct diagnosis of diseases during pregnancy; secondly, it enables us to answer questions about the effects of medication during pregnancy and the ways in which pregnancy alters pharmacokinetic and drug-effects; and thirdly, it allows for proper modeling of physiologically-based pharmacokinetic models, which are increasingly used to predict gestation-specific changes and drug-drug interactions, as well as develop new knowledge on the mode-of-action of drugs, the mechanisms underlying their interactions, and any adverse effects following drug exposure. This paper reviews new evidence regarding the physiologic changes during pregnancy in relation to existing knowledge.

Clearance of buprenorphine during pregnancy and neonatal outcomes

Buprenorphine is emerging as the preferred pharmacologic treatment for opioid use disorder during pregnancy. We examined the relative plasma clearance of buprenorphine (BUP) across pregnancy. Pregnant women with opioid use disorder participating in a prospective, observational study from 2013 to 2016 on stress in pregnancy who were receiving BUP for opioid use disorder were included. Women with an active eating disorder or suicidal ideation were excluded. Research visits occurred at 4-6-week intervals across pregnancy and the early postpartum period and included medication exposure history and blood samples. All assays for BUP serum concentrations at steady state were completed. Relative weight-adjusted clearance (Cl) was calculated using Cl = (daily dose [mg]/ body weight [kg])/serum concentration [ng/ml]. We collected 112 maternal blood samples from 29 women throughout pregnancy and the postpartum period. Serum concentrations for BUP ranged from < 0.2 to 15.8 ng/ml. Eleven women, with greater than three collected samples, increased their daily dose of BUP during pregnancy; however, there were no significant differences in relative clearance of BUP across this same period. This data suggests that women with opioid use disorder receiving BUP did not demonstrate a significant increase in BUP clearance across pregnancy despite increase in dosages during pregnancy. When selecting an appropriate BUP dosage for management of perinatal opioid use disorder, gestational stage appears not to be an important covariate and should be based on an individualized approach.

A review of pregnancy-induced changes in opioid pharmacokinetics, placental transfer, and fetal exposure: Towards fetomaternal physiologically-based pharmacokinetic modeling to improve the treatment of neonatal opioid withdrawal syndrome

Physiologically-based pharmacokinetic (PBPK) modeling has emerged as a useful tool to study pharmacokinetics (PK) in special populations, such as pregnant women, fetuses, and newborns, where practical hurdles severely limit the study of drug behavior. PK in pregnant women is variable and everchanging, differing greatly from that in their nonpregnant female and male counterparts typically enrolled in clinical trials. PBPK models can accommodate pregnancy-induced physiological and metabolic changes, thereby providing mechanistic insights into maternal drug disposition and fetal exposure. Fueled by the soaring opioid epidemic in the United States, opioid use during pregnancy continues to rise, leading to an increased incidence of neonatal opioid withdrawal syndrome (NOWS). The severity of NOWS is influenced by a complex interplay of extrinsic and intrinsic factors, and varies substantially between newborns, but the extent of prenatal opioid exposure is likely the primary driver. Fetomaternal PBPK modeling is an attractive approach to predict in utero opioid exposure. To facilitate the development of fetomaternal PBPK models of opioids, this review provides a detailed overview of pregnancy-induced changes affecting the PK of commonly used opioids during gestation. Moreover, the placental transfer of these opioids is described, along with their disposition in the fetus. Lastly, the implementation of these factors into PBPK models is discussed. Fetomaternal PBPK modeling of opioids is expected to provide improved insights in fetal opioid exposure, which allows for prediction of postnatal NOWS severity, thereby opening the way for precision postnatal treatment of these vulnerable infants.

Addiction treatment in the postpartum period: an opportunity for evidence-based personalized medicine

Substance use disorders (SUD) are becoming rapidly more prevalent in women and a leading cause of pregnancy associated deaths, with most deaths occurring during the 12 months after pregnancy. The postpartum period can be quite intense, especially for women seeking addiction recovery. There is a call to reconceptualize the obstetrical postpartum care model into one that extends specialised care and is tailored to an individual's specific needs. Although SUD treatment improves maternal and infant outcomes as well as decreases overdose risk, many women do not receive consistent SUD treatment during the postpartum period. Thus, SUD treatments should consider following the same guidance as obstetrics to reconceptualize how SUD treatment is delivered postpartum. Clinically, this translates into substantially modifying traditional siloed SUD treatment structures to meet the unique needs of this vulnerable patient population. At the same time, more research is urgently needed to inform these advancements in clinical care to ensure they are evidence-based and effective. In this article, we review the existing evidence as well as highlight opportunities for both clinicians and researchers to advance the integration of tailored approaches for postpartum women into personalised SUD medical and behavioural treatments.

Maternal Exposure and Neonatal Effects of Drugs of Abuse

The public health crisis of pregnant women being exposed to drugs of abuse and of its impact on their unborn children continues to grow at an alarming rate globally. The state of pregnancy is unique, with physiological changes that can lead to changes in the way drugs are handled by the body in both pharmacokinetics and response. These changes place the pregnant woman, fetus, and newborn infant at risk, as many of these drugs can cross the placenta and into breast milk. The substances most commonly linked to harmful effects include alcohol, tobacco, cannabis, stimulants, and opioids. The pharmacological and toxicological changes caused by in utero exposure or breastfeeding exposure are difficult to study, and the full extent of the mechanisms involved are not fully understood. However, these changes can significantly affect the risks of substance abuse and influence optimal treatment of pregnant women with a substance use disorder. In addition, newborns who were exposed to drugs of abuse in utero can experience withdrawal syndromes. Pharmacological management in infants is used to guide and treat withdrawal symptoms, with the goal being to improve the infant's sleep, eating, and comfort. Several barriers may prevent pregnant women from seeking help for substance use, including stigma and interactions with the legal system. Understanding changes in pharmacology, including pharmacokinetic changes that happen during pregnancy, is essential for anticipating the extent of maternal exposure and neonatal adverse effects.

Buprenorphine X-waiver exemption - beyond the basics for the obstetrical provider

Buprenorphine is 1 of 3 medications approved by the US Food and Drug Administration for the treatment of opioid use disorder, and practitioners must obtain a federal waiver to prescribe buprenorphine. Until recently, physicians and advanced practice clinicians were required to complete 8 and 24 hours of training, respectively, before applying for this waiver and to provide psychosocial services when prescribing buprenorphine to ≤30 patients. The US Department of Health and Human Services announced in April 2021 that eligible providers would be exempt from the educational requirement for certification, making the waiver more accessible for those intending to prescribe to ≤30 patients. Here, we reviewed the historic background to the exemption and provided practical guidelines to practitioners caring for obstetrical patients with opioid use disorder who are considering applying for the waiver for the first time. Because the educational requirements will no longer be required for X-waiver application, we reviewed fundamental topics and challenging scenarios that are often reviewed in certification courses.

MATERNAL AND FETAL BUPRENORPHINE PHARMACOKINETICS IN PREGNANT SHEEP DURING TRANSDERMAL PATCH DOSING: Buprenorphine pharmacokinetics in pregnant sheep

BACKGROUND

Buprenorphine is used in the opioid maintenance treatment for opioid dependent patients, including pregnant women. Despite the wide use, limited data exists on buprenorphine pharmacokinetics and fetal exposure during pregnancy. The aim of our study was to determine the buprenorphine pharmacokinetics during transdermal patch dosing to pregnant sheep and, to determine the extent of transplacental transfer of buprenorphine to the fetus.

METHODS

Pregnant sheep in late gestation (n=50) received 20, 25 or 40 µg/h of buprenorphine as a 7-day extended-release transdermal patch. Plasma samples were collected from the ewe and the fetus on days 1 - 6, and buprenorphine and norbuprenorphine concentrations were determined. During the exposure period the sheep had a surgical procedure on the second day, a recovery phase, and an experimental procedure on the sixth day. In the experiment, hypoxia was induced under anesthesia for 18 sheep to investigate if decreased fetal pH would cause ion-trapping of buprenorphine in the fetus. The fetal/maternal plasma concentration ratio was determined on the second and on the sixth exposure day at baseline and during hypoxia. Maternal pharmacokinetics were modelled with a population pharmacokinetic method using the data from this study and our previous intravenous administration study.

RESULTS

The transdermal patch provided an extended release of buprenorphine throughout the exposure period, but the release rate declined approximately 20 h after patch placement. The median fetal/maternal plasma concentration ratio was 13 - 27 % throughout the exposure period at baseline. A ratio over 100 % was observed for four sheep on the sixth exposure day (102 - 269 %). A minor increase was seen in the median fetal/maternal-ratios during maternal hypoxia. Norbuprenorphine was undetected in all plasma samples.

CONCLUSIONS

The low transplacental passage of less than one fourth of the ewe's exposure supports buprenorphine as an alternative to methadone in opioid maintenance therapy during pregnancy.

Obstetrical, fetal, and lactation pharmacology-a crisis that can no longer be ignored

The data available to inform pregnant and lactating women about drug safety and efficacy are woefully inadequate. This lack of information encompasses every aspect of pharmaceutics, including limited human data about the embryonic risk, limited pharmacokinetic and pharmacodynamic information during and after pregnancy to ensure proper dosing, and a dearth of new medications to treat obstetrical and lactation disorders. This state of affairs has been longstanding and can be attributed to several realities, most of which have withstood any efforts to modify them. The first reality is the disinterest of the pharmaceutical industry to undertake pregnancy and lactation studies because of the considerable disincentives to undertake such studies. The medicolegal risks and the limited opportunity for financial gain are significant barriers to their participation. The US Food and Drug Administration has not mandated that new drugs or drugs "on patent" must include studies in pregnant women. Regulatory constrains that have defined pregnant women as a vulnerable class have greatly limited pharmacologic studies. Another contributing factor to this lack of information is the lack of researchers skilled in pharmacology with an interest in the pregnant woman. In addition, although difficult to measure, there is the hesitancy of pregnant and lactating women to participate in pharmacology research either for fear of fetal risk or an inability to commit the time required for such studies. Research in obstetrical and lactation pharmacology lags far behind that of pediatric pharmacology. Through the efforts of many, research in that field is highly funded and very productive in providing new information on medications used in children who, like pregnant women, have differing pharmacologic needs based on age (chronology for children and gestational age for pregnant women). Recently, the deficiencies and possible remedies for this embarrassing state of affairs in obstetrical and lactation pharmacology have been addressed by the federal government, which led to 15 recommendations from the Task Force on Research Specific to Pregnant Women and Lactating Women. In this article, we address the challenges in providing meaningful information about specific medications used by the mother and how these problems have evolved. We also suggest specific strategies to start the process of remediation.

Pregnancy Alters CYP- and UGT-Mediated Metabolism of Buprenorphine

BACKGROUND

In the United States, drug addiction has become a nationwide health crisis. Recently, buprenorphine (BUP), a maintenance therapy approved by the Food and Drug Administration, has been increasingly used in pregnant women for the treatment of opioid use disorder. Pregnancy is associated with various anatomic and physiological changes, which may result in altered drug pharmacokinetics (PKs). Previously, we reported that dose-adjusted plasma concentrations of BUP are lower during pregnancy than after pregnancy. The mechanism(s) responsible for this difference has not yet been defined. Our study aimed to evaluate alterations in cytochromes P450 (CYP)- and uridine diphosphate glucunosyltransferases (UGT)-mediated metabolism of BUP during pregnancy to determine the mechanism(s) responsible for this observation.

METHODS

Data from 2 clinical studies were included in the current analysis. Study 1 was a prospective, open-labeled, nonrandomized longitudinal BUP PK study in pregnant women with a singleton gestation, stabilized on twice-daily sublingual BUP opioid substitution therapy. Each subject participated in up to 3 studies during and after pregnancy (the second, third trimester, and postpartum). The design of study 2 was similar to study 1, with patients evaluated at different time points during the pregnancy (first, second-half of pregnancy), as well as during the postpartum period. In addition, the dosing frequency of BUP study 2 participants was not restricted to twice-daily dosing. At each study visit, blood samples were collected before a BUP dose, followed by multiple collection times (10-12) after the dose, for up to 12 hours or till the end of the dosing interval. Plasma concentrations of BUP and 3 metabolites were quantified using validated ultraperformance liquid chromatography-tandem mass spectrometric assays.

RESULTS

In total, 19, 18, and 14 subjects completed the PK study during 1/2 trimester, third trimester, and postpartum, respectively. The AUC ratios of norbuprenorphine and norbuprenorphine glucuronide to buprenorphine, a measure of CYP3A mediated N-demethylation, were 1.89, 1.84, and 1.33 during the first and second, third trimesters, and postpartum, respectively. The AUC ratios of buprenorphine glucuronide to BUP, indicative of UGT activity, were 0.71, 2.07, and 0.3 at first/second trimesters, third trimester, and postpartum, respectively. Linear mixed-effect modeling analysis indicated that the AUC ratios of CYP- and UGT-mediated metabolism of BUP were significantly higher during pregnancy compared with postpartum.

CONCLUSIONS

The CYP and UGT activities were significantly increased as determined by the metabolic ratios of BUP during pregnancy compared with the postpartum period. The increased UGT activity appeared to account for a substantial part of the observed change in metabolic activity during pregnancy. This is in agreement with the need for BUP dose increment in pregnant women to reach similar BUP exposure and therapeutic effect as in nonpregnant subjects.

Pharmacokinetics of buprenorphine in pregnant sheep after intravenous injection

Buprenorphine is a semi‐synthetic opioid, widely used in the maintenance treatment for opioid‐dependent pregnant women. Limited data exist on the pharmacokinetics of buprenorphine in pregnancy. We conducted a pharmacokinetic study to determine the pharmacokinetics of intravenous buprenorphine in pregnant sheep. Fourteen pregnant sheep in late gestation received 10 µg/kg of buprenorphine as an intravenous bolus injection. Plasma samples were collected up to 48 h after administration. Buprenorphine and its metabolite, norbuprenorphine, were quantified from plasma using a LC/MS/MS method, with lower limits of quantification of 0.01 µg/L and 0.04 µg/L for buprenorphine and norbuprenorphine, respectively. The pharmacokinetic parameters were calculated using noncompartmental analysis. The pharmacokinetic parameters, median (minimum−maximum), were C_max 4.31 µg/L (1.93–15.5), AUC_inf 2.89 h*µg/L (1.72–40.2), CL 3.39 L/h/kg (0.25–6.02), terminal t½ 1.75 h (1.07–31.0), V_ss 8.04 L/kg (1.05–49.3). Norbuprenorphine was undetected in all plasma samples. The median clearance in pregnant sheep was higher than previously reported for nonpregnant sheep and human (male) subjects. Our sensitive analytical method was able to detect long terminal half‐lives for six subjects, and a wide between‐subject variability in the study population.

Significance statement: Buprenorphine is widely used for the treatment of opioid use disorder in pregnancy. However, limited data exist on the pharmacokinetics of buprenorphine during pregnancy. As this type of study cannot be done in humans due to ethical reasons, we conducted a study in pregnant sheep. This study provides pharmacokinetic data on buprenorphine in pregnant sheep and helps us to understand the pharmacokinetics of the drug in humans.

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.

Pharmacokinetic Characterization and External Evaluation of a Quantitative Framework of Sublingual Buprenorphine in Patients with an Opioid Disorder in Puerto Rico

Background: The aim of this analysis was to characterize the pharmacokinetics (PK) of sublingual buprenorphine (BUP) and its metabolites (buprenorphine glucuronide; BUP-g, norbuprenorphine; Nor-BUP, and norbuprenorphine glucuronide; Nor-BUP-g) in opioid use disorder (OUD) patients in Puerto Rico (PR) as a first step of evidence-based BUP dosing strategies in this population. Methods: BUP and metabolites concentrations were measured from 0 to 8 h after the administration of sublingual buprenorphine/naloxone films in 12 stable OUD subjects. Results: PK non-compartmental characteristics showed considerable variability in parameters between the subjects over the 8-h sampling time (t_max = 1.5 ± 0.7 h, C_o = 1.6 ± 1.4 ng/mL, C_max= 7.1 ± 6 ng/mL, and AUC_0–8h = 26.8 ± 17.8 h·ng/mL). Subjects had a significantly higher tendency towards CYP-mediated N-demethylation, with the AUC_0–8h ratios of the molar concentrations of [Nor-BUP + Nor-BUP-g] to BUP being (3.4 ± 1.9) significantly higher compared with BUP-g to BUP (0.19 ± 0.2). A two-compartment population-PK model with linear absorption (k_a = 2.54 h⁻¹), distribution (k₁₂= 2.34 h⁻¹, k₁₄ = 1.29 h⁻¹), metabolism (k₂₄ = 1.28 × 10⁻¹ h⁻¹, k₂₃ = 6.43 × 10⁻² h⁻¹, k₃₅ = 1.23 × 10⁻¹ h⁻¹, k₄₅ = 8.73 × 10⁻¹ h⁻¹), and elimination (k₃₀ = 3.81 × 10⁻³ h⁻¹, k₅₀ = 1.27 × 10⁻¹ h⁻¹) adequately described the time-course of BUP and its metabolites, which has been externally validated using published data. Conclusions: Although limited in sampling time and number of recruited subjects, this study presents specific BUP PK characteristics that evidenced the need for additional PK studies and subsequent modeling of the data for the development of evidence-based dosing approaches in Puerto Rico.

Rapid Buprenorphine Induction for Cancer Pain in Pregnancy

Most patients with cancer-related pain are managed using opioids; cancer-related pain in the setting of pregnancy can be challenging to address owing to risk to the fetus associated with in utero opioid exposure. Buprenorphine is a unique opioid with potential benefits over other opioids for use in pregnancy and is often used for management of cancer-related pain in nonpregnant adults. There are limited data on cancer-related pain management in pregnant patients and no data supporting the use of buprenorphine for cancer-related pain in pregnant patients. This case describes a rapid buprenorphine induction using a microdosing regimen in a pregnant patient and highlights the potential of buprenorphine for cancer-related pain in this population.

Early lessons from maternal mortality review committees on drug-related deaths-time for obstetrical providers to take the lead in addressing addiction

Problem:

In the United States, maternal mortality review committees (MMRC) are providing compelling data that drug-related deaths are emerging as a leading cause of pregnancy-associated death (death during pregnancy or up to a year postpartum). Recommendations from the MMRC consistently highlight screening all pregnant and postpartum women for drug use and improving access to evidence-based substance use disorder and mental health treatment. Unfortunately, many providers lack the confidence, skills and necessary resources to screen for substance use, provide basic behavioral health services or facilitate referral to high-quality services in their clinical settings. Our profession’s collective lack of response to a leading cause of maternal death represents a missed opportunity for potentially life-saving interventions.

A Solution:

We call on our fellow obstetrician gynecologists to incorporate the lessons learned from MMRC and integrate addiction assessment and treatment into prenatal and postpartum care. Provider level integration of behavioral health services is, however, insufficient to fully address the magnitude of drug-related maternal deaths in the US. We, therefore, ask colleagues to address the structural/systemic barriers to care identified in MMRC. By doing so, we can prevent drug-related maternal deaths.

Buprenorphine dosing for the treatment of opioid use disorder through pregnancy and postpartum

PURPOSE OF REVIEW

Opioid-related deaths are a leading cause of mortality during pregnancy through 12 months postpartum. Buprenorphine use during pregnancy is increasing, yet expert opinion on its dosing through the perinatal period is limited. We provide a review of the current clinical literature on buprenorphine dosing during pregnancy through 12 months postpartum. and present data from a retrospective chart review of patients at our institution describing trends in buprenorphine dosing during pregnancy and postpartum. Utilizing this information, we synthesize findings to provide clinical recommendations for providers.

RECENT FINDINGS

Existing literature during pregnancy reflects how many women increase and split total daily buprenorphine doses as gestational age advances.

SUMMARY

We present data from a retrospective chart review of patients at our institution describing trends in buprenorphine dosing during pregnancy and postpartum. Utilizing this information, we synthesize findings to provide clinical recommendations for providers. Changes in the total daily dose of buprenorphine used across pregnancy and through 12 months postpartum at the individual level do not follow consistent patterns, highlighting substantial individual variability. Altogether, buprenorphine dosing should be individualized through pregnancy and postpartum with frequent evaluations by providers and solicited input from patients.

Drug dosing during pregnancy-opportunities for physiologically based pharmacokinetic models

Drugs can have harmful effects on the embryo or the fetus at any point during pregnancy. Not all the damaging effects of intrauterine exposure to drugs are obvious at birth, some may only manifest later in life. Thus, drugs should be prescribed in pregnancy only if the expected benefit to the mother is thought to be greater than the risk to the fetus. Dosing of drugs during pregnancy is often empirically determined and based upon evidence from studies of non-pregnant subjects, which may lead to suboptimal dosing, particularly during the third trimester. This review collates examples of drugs with known recommendations for dose adjustment during pregnancy, in addition to providing an example of the potential use of PBPK models in dose adjustment recommendation during pregnancy within the context of drug-drug interactions. For many drugs, such as antidepressants and antiretroviral drugs, dose adjustment has been recommended based on pharmacokinetic studies demonstrating a reduction in drug concentrations. However, there is relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Examples of using pregnancy PBPK models to predict feto-maternal drug exposures and their applications to facilitate and guide dose assessment throughout gestation are discussed.

Dispersive solid-phase extraction of buprenorphine from biological fluids using metal-organic frameworks and its determination by ultra-performance liquid chromatography

In this work, various types of metal-organic frameworks were synthesized, and their affinities toward buprenorphine were evaluated using dispersive solid-phase extraction. The extracted buprenorphine was determined by ultra high performance liquid chromatography-ultraviolet detection system. The highest extraction recovery was observed by employing zeolitic imidazole framework-67. Then, a facile and fast extraction method was designed for the extraction and purification of the target drug. Optimization of the extraction method was carried out by the design of experiment approach. A linearity range of 1-1000 μg/L with the limit of detection of 0.15 μg/L and relative standard deviations (50 μg/L, n = 5) of 3.4% was obtained for standard sample analysis. Under optimized experimental and instrumental conditions, the relative recoveries were in the range of 95 to 111%. Eventually, zeolitic imidazole framework-67 was successfully employed for the extraction and determination of buprenorphine in the biological fluids with satisfactory results.

Building a Group-Based Opioid Treatment (GBOT) blueprint: a qualitative study delineating GBOT implementation

BACKGROUND

Group-Based Opioid Treatment (GBOT) has recently emerged as a mechanism for treating patients with opioid use disorder (OUD) in the outpatient setting. However, the more practical "how to" components of successfully delivering GBOT has received little attention in the medical literature, potentially limiting its widespread implementation and utilization. Building on a previous case series, this paper delineates the key components to implementing GBOT by asking: (a) What are the core components to GBOT implementation, and how are they defined? (b) What are the malleable components to GBOT implementation, and what conceptual framework should providers use in determining how to apply these components for effective delivery in their unique clinical environment?

METHODS

To create a blueprint delineating GBOT implementation, we integrated findings from a previously conducted and separately published systematic review of existing GBOT studies, conducted additional literature review, reviewed best practice recommendations and policies related to GBOT and organizational frameworks for implementing health systems change. We triangulated this data with a qualitative thematic analysis from 5 individual interviews and 2 focus groups representing leaders from 5 different GBOT programs across our institution to identify the key components to GBOT implementation, distinguish "core" and "malleable" components, and provide a conceptual framework for considering various options for implementing the malleable components.

RESULTS

We identified 6 core components to GBOT implementation that optimize clinical outcomes, comply with mandatory policies and regulations, ensure patient and staff safety, and promote sustainability in delivery. These included consistent group expectations, team-based approach to care, safe and confidential space, billing compliance, regular monitoring, and regular patient participation. We identified 14 malleable components and developed a novel conceptual framework that providers can apply when deciding how to employ each malleable component that considers empirical, theoretical and practical dimensions.

CONCLUSION

While further research on the effectiveness of GBOT and its individual implementation components is needed, the blueprint outlined here provides an initial framework to help office-based opioid treatment sites implement a successful GBOT approach and hence potentially serve as future study sites to establish efficacy of the model. This blueprint can also be used to continuously monitor how components of GBOT influence treatment outcomes, providing an empirical framework for the ongoing process of refining implementation strategies.

Pain, Opioids, and Pregnancy: Historical Context and Medical Management

Women are being disproportionately affected by the opioid crisis, including during pregnancy. Pain and other vulnerabilities to addiction differ between men and women. Management of opioid use disorder should be gender informed and accessible across the lifespan. During pregnancy, care teams should be multidisciplinary to include obstetrics, addiction, social work, anesthesia, pediatrics, and behavioral health. Pain management for women with opioid use disorder requires tailored approaches, including integration of trauma-informed care and addressing psychosocial needs. Thus, coordinated continued care by obstetric and addiction providers through pregnancy into postpartum is key to supporting women in recovery.

Opioid use disorder in pregnancy

The number of pregnant people affected by the opioid epidemic in the United States continues to rise. The following key aspects of opioid use disorder in pregnancy are explored through the progression of a pregnancy via a patient case: treatment options, treatment decisions, substance use screening, dosing modifications, and other aspects of peripartum care. Many factors affect opioid use disorder treatment choices during pregnancy; however, when a pregnant person is medically eligible for a therapy and multiple options are available locally, the ultimate decision regarding treatment selection should be left up to the patient and strong support services provided. This approach to treatment results in optimal maternal and neonatal outcomes and long-term maternal engagement and retention in care.

The Pregnancy Recovery Center: A women-centered treatment program for pregnant and postpartum women with opioid use disorder

OBJECTIVE

To evaluate the impact of women-centered substance abuse treatment programming on outcomes among pregnant women with opioid use disorder (OUD).

METHODS

We compared two retrospective cohorts of pregnant women with OUD on buprenorphine maintenance therapy who delivered an infant at the University of Pittsburgh from 2014 to 2016. Cohort 1 was composed of pregnant women who received women-centered OUD treatment services through the Pregnancy Recovery Program (PRC) and Cohort 2 was composed of pregnant women who received buprenorphine at OUD programs without women-centered services (non-PRC). Women-centered outcomes were defined as a) pregnancy-specific buprenorphine dosing, b) prenatal and postpartum care attendance, c) breastfeeding and d) highly effective contraception utilization. Chi-square and t-tests were used to compare outcomes between PRC and non-PRC patients.

RESULTS

Among 248 pregnant women with OUD, 71 (28.6%) were PRC and 177 (71.4%) were non-PRC patients. PRC patients were significantly more likely to initiate buprenorphine during vs. prior to their pregnancy (81.4% vs. 44.2%; p < .01) and have a higher buprenorphine dose at the time of delivery (16.0 mg vs. 14.1 mg; p = .02) compared to non-PRC patients. Likewise, PRC patients were significantly more likely to attend their postpartum visit (67.9% vs. 52.6%; p = .05) and receive a long-acting reversible contraceptive (LARC) method (23.9% vs. 13.0%, p = .03) after delivery compared to non-PRC patients. Finally, PRC patients had a smaller percent decrease in the rate of breastfeeding during their delivery hospitalization (-14.7% vs. -37.1%).

CONCLUSIONS

Incorporating women-centered services into OUD treatment programming may improve gender-specific outcomes among women with OUD.

Adherence trajectories of buprenorphine therapy among pregnant women in a large state Medicaid program in the United States

PURPOSE

Little is known about the longitudinal patterns of buprenorphine adherence among pregnant women with opioid use disorder, especially when late initiation, nonadherence, or early discontinuation of buprenorphine during pregnancy may increase the risk of adverse outcomes. We aimed to identify distinct trajectories of buprenorphine use during pregnancy, and factors associated with these trajectories in Medicaid-enrolled pregnant women.

METHODS

A retrospective cohort study included 2361 Pennsylvania Medicaid enrollees aged 15 to 46 having buprenorphine therapy during pregnancy and a live birth between 2008 and 2015. We used group-based trajectory models to identify buprenorphine use patterns in the 40 weeks prior to delivery and 12 weeks postdelivery. Multivariable multinomial logistic regression models were used to identify factors associated with specific trajectories.

RESULTS

Six distinct trajectories were identified. Four groups initiated buprenorphine during the first trimester of the pregnancy (early initiators): 31.6% with persistently high adherence, 15.1% with moderate-to-high adherence, 10.5% with declining adherence, and 16.7% with early discontinuation. Two groups did not initiate buprenorphine until midsecond or third trimester (late initiators): 13.5% had moderate-to-high adherence and 12.6% had low-to-moderate adherence. Factors significantly associated with late initiation and discontinuation were younger age, non-white race, residents of rural counties, fewer outpatient visits, more frequent emergency department visits and hospitalizations, and lower buprenorphine daily dose.

CONCLUSIONS

Six buprenorphine treatment trajectories during pregnancy were identified in this population-based Medicaid cohort, with 25% of women initiating buprenorphine late during pregnancy. Understanding trajectories of buprenorphine use and factors associated with discontinuation/nonadherence may guide integration of behavioral treatment with obstetrical/gynecological care to improve buprenorphine treatment during pregnancy.

Gestational changes in buprenorphine exposure: A physiologically-based pharmacokinetic analysis

AIMS

Buprenorphine (BUP) is approved by the US Food and Drug Administration for the treatment of opioid addiction. The current dosing regimen of BUP in pregnant women is based on recommendations designed for nonpregnant adults. However, physiological changes during pregnancy may alter BUP exposure and efficacy. The objectives of this study were to develop a physiologically-based pharmacokinetic (PBPK) model for BUP in pregnant women, to predict changes in BUP exposure at different stages of pregnancy, and to demonstrate the utility of PBPK modelling in optimizing BUP pharmacotherapy during pregnancy.

METHODS

A full PBPK model for BUP was initially built and validated in healthy subjects. A fetoplacental compartment was included as a combined compartment in this model to simulate pregnancy induced anatomical and physiological changes. Further, gestational changes in physiological parameters were incorporated in this model. The PBPK model predictions of BUP exposure in pregnancy and during the postpartum period were compared to published data from a prospective clinical study.

RESULTS

The predicted BUP plasma concentration-time profiles in the virtual pregnant populations are consistent with the observed data in the 2nd and 3rd trimesters, and the postpartum period. The differences in the predicted means of dose normalized area under the plasma drug concentration-time curve up to 12 h, average concentration and maximum concentration were within ±25% of the corresponding observed means with the exception of average concentration in the 3rd trimester (-26.3%).

CONCLUSION

PBPK model-based simulation may be a useful tool to optimize BUP pharmacotherapy during pregnancy, obviating the need to perform pharmacokinetic studies in each trimester and the postpartum period that normally require intensive blood sampling.

Opioid Use Disorders and Pregnancy

Opioid use disorder presents an increased risk of complications in pregnancy, particularly when untreated. To optimize outcomes, medication-assisted treatment using methadone or buprenorphine as a part of a comprehensive care model is recommended. Neonatal abstinence syndrome and poor fetal growth remain significant complications of this disorder despite maternal treatment.

Pregnancy Increases Norbuprenorphine Clearance in Mice by Induction of Hepatic Glucuronidation

Norbuprenorphine (NBUP) is the major active metabolite of buprenorphine (BUP) that is commonly used to treat opiate addiction during pregnancy; it possesses 25% of BUP's analgesic activity and 10 times BUP's respiratory depression effect. To optimize BUP's dosing regimen during pregnancy with better efficacy and safety, it is important to understand how pregnancy affects NBUP disposition. In this study, we examined the pharmacokinetics of NBUP in pregnant and nonpregnant mice by administering the same amount of NBUP through retro-orbital injection. We demonstrated that the systemic clearance (CL) of NBUP in pregnant mice increased ∼2.5-fold compared with nonpregnant mice. Intrinsic CL of NBUP by glucuronidation in mouse liver microsomes from pregnant mice was ∼2 times greater than that from nonpregnant mice. Targeted liquid chromatography tandem-mass spectrometry proteomics quantification revealed that hepatic Ugt1a1 and Ugt2b1 protein levels in the same amount of total liver membrane proteins were significantly increased by ∼50% in pregnant mice versus nonpregnant mice. After scaling to the whole liver with consideration of the increase in liver protein content and liver weight, we found that the amounts of Ugt1a1, Ugt1a10, Ugt2b1, and Ugt2b35 protein in the whole liver of pregnant mice were significantly increased ∼2-fold compared with nonpregnant mice. These data suggest that the increased systemic CL of NBUP in pregnant mice is likely caused by an induction of hepatic Ugt expression and activity. The data provide a basis for further mechanistic analysis of pregnancy-induced changes in the disposition of NBUP and drugs that are predominately and extensively metabolized by Ugts.

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.