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

Consensus Panel Recommendations for the Pharmacological Management of Breastfeeding Women with Postpartum Depression

INTRODUCTION

Our consensus statement aims to clarify the use of antidepressants and anxiolytics during breastfeeding amidst clinical uncertainty. Despite recent studies, potential harm to breastfed newborns from these medications remains a concern, leading to abrupt discontinuation of necessary treatments or exclusive formula feeding, depriving newborns of benefits from mother's milk.

METHODS

A panel of 16 experts, representing eight scientific societies with a keen interest in postpartum depression, was convened. Utilizing the Nominal Group Technique and following a comprehensive literature review, a consensus statement on the pharmacological treatment of breastfeeding women with depressive disorders was achieved.

RESULTS

Four key research areas were delineated: (1) The imperative to address depressive and anxiety disorders during lactation, pinpointing the risks linked to untreated maternal depression during this period. (2) The evaluation of the cumulative risk of unfavorable infant outcomes associated with exposure to antidepressants or anxiolytics. (3) The long-term impact on infants' cognitive development or behavior due to exposure to these medications during breastfeeding. (4) The assessment of pharmacological interventions for opioid abuse in lactating women diagnosed with depressive disorders.

CONCLUSIONS

The ensuing recommendations were as follows: Recommendation 1: Depressive and anxiety disorders, as well as their pharmacological treatment, are not contraindications for breastfeeding. Recommendation 2: The Panel advocates for the continuation of medication that has demonstrated efficacy during pregnancy. If initiating an antidepressant during breastfeeding is necessary, drugs with a superior safety profile and substantial epidemiological data, such as SSRIs, should be favored and prescribed at the lowest effective dose. Recommendation 3: For the short-term alleviation of anxiety symptoms and sleep disturbances, the Panel determined that benzodiazepines can be administered during breastfeeding. Recommendation 4: The Panel advises against discontinuing opioid abuse treatment during breastfeeding. Recommendation 5: The Panel endorses collaboration among specialists (e.g., psychiatrists, pediatricians, toxicologists), promoting multidisciplinary care whenever feasible. Coordination with the general practitioner is also recommended.

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.

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 (EC50 = 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 EC50 for newborns must be confirmed.

Comparison of immunoassay and LC-tandem mass spectrometry analyses of ractopamine in hog oral fluid

The accurate detection of ractopamine in food animals is crucial for marketing since some entities require animals or animal carcasses to be free of ractopamine residues. Field-based ractopamine screening tests that are rapid, sensitive, and capable of high-throughput are highly desirable to ensure that inadvertent exposure to ractopamine did not occur in animals marketed as animals that have not been fed ractopamine. An immunochemically based lateral flow assay was used to analyze oral fluids from hogs never exposed to ractopamine and from hogs that were presumed positives and results were confirmed using an enhanced sensitivity LC-MSMS method. We found that an immunochemically based lateral flow system having a working range of 2.5 to 15 ng mL-1 worked well as a screening assay with 1.7% false positive results in freshly collected hog oral fluids. Using ractopamine glucuronide standards and LC-MSMS, we determined that the false positive results were not due to the presence of ractopamine glucuronide metabolites in oral fluids.

Oral Cavity Fluid as an Alternative Postmortem Matrix: Comparison to Simultaneously Collected Blood and Urine Specimens

ABSTRACT

In postmortem toxicology analysis, a variety of specimens consisting of fluids and tissues are often collected, each with an intrinsic value. Oral cavity fluid (OCF) is emerging as an alternative matrix in forensic toxicology for contributing to a diagnosis in postmortem cases; especially when blood is limited or not available. The aim of this study was to assess the analytical results obtained from OCF and compare them with blood, urine, and other traditional matrices collected from the same postmortem subjects. Of the 62 decedents studied (including 1 stillborn, 1 charred, and 3 decomposed subjects), 56 had quantifiable drugs and metabolites data in the OCF, blood, and urine. Notable findings were benzoylecgonine (24 cases), ethyl sulfate (23 cases), acetaminophen (21 cases), morphine (21 cases), naloxone (21 cases), gabapentin (20 cases), fentanyl (17 cases), and 6-acetylmorphine (15 cases), which were detected more frequently in OCF than in blood (heart, femoral, or body cavity) or urine. This study suggests that OCF is a suitable matrix for detecting and quantifying analytes in postmortem subjects compared with traditional matrices, particularly when other matrices are limited or difficult to collect because of body condition or putrefaction.

Interaction between buprenorphine and norbuprenorphine in neonatal opioid withdrawal syndrome

Buprenorphine (BUP) is the preferred treatment for opioid use disorder during pregnancy but can cause neonatal opioid withdrawal syndrome (NOWS). Norbuprenorphine (NorBUP), an active metabolite of BUP, is implicated in BUP-associated NOWS. We hypothesized that BUP, a low-efficacy agonist of mu opioid receptors, will not antagonize NorBUP, a high-efficacy agonist of mu opioid receptors, in producing NOWS. To test this hypothesis, we treated pregnant Long-Evans rats with BUP (0, 0.01, 0.1 or 1mg/kg/day) ± NorBUP (1mg/kg/day) from gestation day 9 until pup delivery, and tested pups for opioid dependence using our established NOWS model. We used LC-MS-MS to quantify brain concentrations of BUP, NorBUP, and their glucuronide conjugates. BUP had little effect on NorBUP-induced NOWS, with the exception of 1mg/kg/day BUP significantly increasing NorBUP-induced NOWS by 58% in females. BUP and NorBUP brain concentrations predicted NOWS in multiple linear regression models. Interestingly, NorBUP contributed more to NOWS in females (βNorBUP = 51.34, p = 0.0001) than in males (βNorBUP = 19.21, P = 0.093), while BUP was similar for females (βBUP = 10.62, P = 0.0017) and males (βBUP = 11.38, P = 0.009). We are the first to report that NorBUP induces NOWS in the presence of BUP and it is more influential in females than males in the contribution of NorBUP to BUP-associated NOWS. These findings suggest that females are more susceptible to NorBUP-induced NOWS, and that treatment strategies that reduce prenatal NorBUP exposure may be more effective for females than males.

Harmful effects of opioid use in pregnancy: A scientific review commissioned by the European Board and College of obstetrics and gynaecology (EBCOG)

Caring for pregnant women who have a recreational opioid use disorder is a common clinical challenge in modern obstetric care. These are an elusive population who often have multiple social issues that complicate their pregnancy management. Comprehensive and supportive maternal care can motivate these mothers to change her lifestyle. Multidisciplinary non-judgemental approach with appropriate medication and management, can result in good pregnancy outcomes for mother and her baby.

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.

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.

Medication-Assisted Treatment for Opioid Use Disorder in Pregnancy: Practical Applications and Clinical Impact

Importance

Opioid use disorder is increasingly common in the United States and affects many pregnancies. Given the rise in pregnancies complicated by opioid use, providers should understand the diagnosis and management of opioid use disorder in pregnancy.

Objective

This article focuses on screening for opioid misuse, selecting appropriate treatment for patients, initiating medication-assisted treatment in the inpatient setting, and providing appropriate peripartum care.

Evidence Acquisition

A PubMed search was undertaken using the following search terms: "opioid use disorder", "pregnancy," "medication assisted treatment," "buprenorphine," "methadone," "heroin," "addiction," "neonatal abstinence syndrome," and "detoxification." The search was limited to the English language publications, with most being published after 2000.

Results

All women should be screened for opioid use disorder during pregnancy. Opioid use has profound effects on the mother and infant. Medication-assisted treatment is the standard of care for pregnant women with opioid use disorder. Patients will require a multidisciplinary approach to management in the intrapartum and postpartum period.

Conclusions

Conclusions

Opioid use disorder is a common, chronic condition with significant implications during pregnancy. Recognition and appropriate treatment of this disorder can optimize maternal and fetal outcomes.

Conclusions

Obstetricians are increasingly being challenged to manage pregnancies complicated by opioid use disorder and should be proficient in providing safe and effective care.

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.

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.

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.

Oral Fluid Drug Testing: Analytical Approaches, Issues and Interpretation of Results

With advances in analytical technology and new research informing result interpretation, oral fluid (OF) testing has gained acceptance over the past decades as an alternative biological matrix for detecting drugs in forensic and clinical settings. OF testing offers simple, rapid, non-invasive, observed specimen collection. This article offers a review of the scientific literature covering analytical methods and interpretation published over the past two decades for amphetamines, cannabis, cocaine, opioids, and benzodiazepines. Several analytical methods have been published for individual drug classes and, increasingly, for multiple drug classes. The method of OF collection can have a significant impact on the resultant drug concentration. Drug concentrations for amphetamines, cannabis, cocaine, opioids, and benzodiazepines are reviewed in the context of the dosing condition and the collection method. Time of last detection is evaluated against several agencies' cutoffs, including the proposed Substance Abuse and Mental Health Services Administration, European Workplace Drug Testing Society and Driving Under the Influence of Drugs, Alcohol and Medicines cutoffs. A significant correlation was frequently observed between matrices (i.e., between OF and plasma or blood concentrations); however, high intra-subject and inter-subject variability precludes prediction of blood concentrations from OF concentrations. This article will assist individuals in understanding the relative merits and limitations of various methods of OF collection, analysis and interpretation.

In Utero Exposure to Norbuprenorphine, a Major Metabolite of Buprenorphine, Induces Fetal Opioid Dependence and Leads to Neonatal Opioid Withdrawal Syndrome

Buprenorphine is the preferred treatment of opioid use disorder during pregnancy but can cause fetal opioid dependence and neonatal opioid withdrawal syndrome (NOWS). Notably, withdrawal severity is independent of maternal buprenorphine dose, suggesting that interindividual variance in pharmacokinetics may influence risk and severity of NOWS. Using a rat model of NOWS, we tested the hypothesis that clinically relevant doses of the active metabolite norbuprenorphine (NorBUP) can induce in utero opioid dependence, manifested as naltrexone-precipitated withdrawal signs in the neonate. Pregnant Long-Evans rats were implanted with 14-day osmotic minipumps containing vehicle, morphine (positive control), or NorBUP (0.3-10 mg/kg per day) on gestation day 9. By 12 hours post-delivery, an intraperitoneal injection of the opioid antagonist naltrexone (1 or 10 mg/kg) or saline was administered to pups. Precipitated withdrawal signs were graded by raters blinded to treatment conditions. In a separate group, NorBUP concentrations in maternal and fetal blood and brain on gestation day 20 were determined by liquid chromatography-tandem mass spectrometry. Steady-state maternal blood concentrations of NorBUP in dams infused with 1 or 3 mg/kg per day were comparable to values reported in pregnant humans treated with buprenorphine (1.0 and 9.6 ng/ml, respectively), suggesting a clinically relevant dosing regimen. At these doses, NorBUP increased withdrawal severity in the neonate as shown by an evaluation of 10 withdrawal indicators. These findings support the possibility that NorBUP contributes to fetal opioid dependence and NOWS following maternal buprenorphine treatment during pregnancy.

Opioid Use in Pregnant Women and Neonatal Abstinence Syndrome-A Review of the Literature

Opiate use during pregnancy has been an increasing problem over the last two decades, making it an important social and health concern. The use of such substances may have serious negative outcomes in the newborn, and clinical and cognitive conditions have been reported, including neonatal abstinence syndrome, developmental problems, and lower cognitive performance. These conditions are common when opiates are used during pregnancy, making the prescription of these kinds of drugs problematic. Moreover, the mother may develop opiate addiction, thus, increasing the likelihood of the infant being born with any of those conditions. This paper reviews the use of opiates during pregnancy and focuses mainly on the neonatal abstinence syndrome. First, the commonly prescribed opiates will be identified, namely those usually involved in cases of addiction and/or neonatal abstinence syndrome. Second, published approaches to deal with those problems will be presented and discussed, including the treatment of both the mother and the infant. Finally, we will outline the treatments that are safest and most efficient, and will define future goals, approaches, and research directions for the scientific community regarding this problem.

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.

Urine and oral fluid drug testing in support of pain management

In recent years, the abuse of opioid drugs has resulted in greater prevalence of addiction, overdose, and deaths attributable to opioid abuse. The epidemic of opioid abuse has prompted professional and government agencies to issue practice guidelines for prescribing opioids to manage chronic pain. An important tool available to providers is the drug test for use in the initial assessment of patients for possible opioid therapy, subsequent monitoring of compliance, and documentation of suspected aberrant drug behaviors. This review discusses the issues that most affect the clinical utility of drug testing in chronic pain management with opioid therapy. It focuses on the two most commonly used specimen matrices in drug testing: urine and oral fluid. The advantages and disadvantages of urine and oral fluid in the entire testing process, from specimen collection and analytical methodologies to result interpretation are reviewed. The analytical sensitivity and specificity limitations of immunoassays used for testing are examined in detail to draw attention to how these shortcomings can affect result interpretation and influence clinical decision-making in pain management. The need for specific identification and quantitative measurement of the drugs and metabolites present to investigate suspected aberrant drug behavior or unexpected positive results is analyzed. Also presented are recent developments in optimization of test menus and testing strategies, such as the modification of the standard screen and reflexed-confirmation testing model by eliminating some of the initial immunoassay-based tests and proceeding directly to definitive testing by mass spectrometry assays.

An evidence-based recommendation to increase the dosing frequency of buprenorphine during pregnancy

BACKGROUND

Dose-adjusted plasma concentrations of buprenorphine are significantly decreased during pregnancy compared with the nonpregnant state. This observation suggests that pregnant women may need a higher dose of buprenorphine than nonpregnant individuals to maintain similar drug exposure (plasma concentrations over time after a dose). The current dosing recommendations for buprenorphine during pregnancy address the total daily dose of buprenorphine to be administered, but the frequency of dosing is not clearly addressed. Based on buprenorphine's long terminal half-life, once-daily or twice-daily dosing has generally been suggested.

OBJECTIVE

The objective of the study was to assess the impact of dosing frequency on buprenorphine plasma concentration time course during pregnancy.

STUDY DESIGN

We utilized 3 data sources to determine an optimal frequency for dosing of buprenorphine during pregnancy: data from a pharmacokinetic study of 14 pregnant and postpartum women on maintenance buprenorphine in a supervised clinical setting; data from pregnant women attending a buprenorphine clinic; and data from a physiologically based pharmacokinetic modeling of buprenorphine pharmacokinetics in nonpregnant subjects.

RESULTS

Among the 14 women participating in the pharmacokinetic study during and after pregnancy, plasma concentrations of buprenorphine were <1 ng/mL (the theoretical concentration required to prevent withdrawal symptoms) for 50-80% of the 12 hour dosing interval while at steady state. Among 62 women followed up in a opioid agonist treatment program, in which dosing frequency is determined in part by patient preference, 10 (16%) were on once-daily dosing, 10 (16%) were on twice-daily dosing, 28 (45%) were on thrice-daily dosing, and 14 (23%) were on four-times-daily dosing. A physiologically based pharmacokinetic model in nonpregnant subjects demonstrated that dosing frequency has an impact on the duration over which the plasma concentrations are below a specified plasma concentration threshold.

CONCLUSION

A more frequent dosing interval (ie, three-times-daily or four-times-daily dosing) may be required in pregnant women to sustain plasma concentrations above the threshold of 1 ng/mL to prevent withdrawal symptoms and to improve adherence.

P-gp/ABCB1 exerts differential impacts on brain and fetal exposure to norbuprenorphine

Norbuprenorphine is the major active metabolite of buprenorphine which is commonly used to treat opiate addiction during pregnancy. Norbuprenorphine produces marked respiratory depression and was 10 times more potent than buprenorphine. Therefore, it is important to understand the mechanism that controls fetal exposure to norbuprenorphine, as exposure to this compound may pose a significant risk to the developing fetus. P-gp/ABCB1 and BCRP/ABCG2 are two major efflux transporters regulating tissue distribution of drugs. Previous studies have shown that norbuprenorphine, but not buprenorphine, is a P-gp substrate. In this study, we systematically examined and compared the roles of P-gp and BCRP in determining maternal brain and fetal distribution of norbuprenorphine using transporter knockout mouse models. We administered 1mg/kg norbuprenorphine by retro-orbital injection to pregnant FVB wild-type, Abcb1a^-/-/1b^-/-, and Abcb1a^-/-/1b^-/-/Abcg2^-/- mice on gestation day 15. The fetal AUC of norbuprenorphine was ∼64% of the maternal plasma AUC in wild-type mice, suggesting substantial fetal exposure to norbuprenorphine. The maternal plasma AUCs of norbuprenorphine in Abcb1a^-/-/1b^-/- and Abcb1a^-/-/1b^-/-/Abcg2^-/- mice were ∼2 times greater than that in wild-type mice. Fetal AUCs in Abcb1a^-/-/1b^-/- and Abcb1a^-/-/1b^-/-/Abcg2^-/- mice were also increased compared to wild-type mice; however, the fetal-to-maternal plasma AUC ratio remained relatively unchanged by the knockout of Abcb1a/1b or Abcb1a/1b/Abcg2. In contrast, the maternal brain-to-maternal plasma AUC ratio in Abcb1a^-/-/1b^-/- or Abcb1a^-/-/1b^-/-/Abcg2^-/- mice was increased ∼30-fold compared to wild-type mice. Protein quantification by LC-MS/MS proteomics revealed significantly higher amounts of P-gp protein in the wild-type mice brain than that in the placenta. These results indicate that fetal exposure to norbuprenorphine is substantial and that P-gp has a minor impact on fetal exposure to norbuprenorphine, but plays a significant role in restricting its brain distribution. The differential impacts of P-gp on norbuprenorphine distribution into the brain and fetus are likely, at least in part, due to the differences in amounts of P-gp protein expressed in the blood-brain and blood-placental barriers. BCRP is not as important as P-gp in determining both the systemic and tissue exposure to norbuprenorphine. Finally, fetal AUCs of the metabolite norbuprenorphine-β-d-glucuronide were 3-7 times greater than maternal plasma AUCs, while the maternal brain AUCs were <50% of maternal plasma AUCs, suggesting that a reversible pool of conjugated metabolite in the fetus may contribute to the high fetal exposure to norbuprenorphine.

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

BACKGROUND

Buprenorphine is a Food and Drug Administration-approved maintenance therapy for opioid use disorders and is increasingly being used in pregnant women with opioid use disorders as an alternative to methadone. Dosing of buprenorphine in pregnant women is based on the regimen recommended for nonpregnant females and males. Limited data are available defining the pharmacokinetic properties of sublingual buprenorphine administered during pregnancy.

OBJECTIVE

This study evaluated the impact of physiological changes associated with pregnancy on the pharmacokinetics of sublingual buprenorphine during and after pregnancy.

STUDY DESIGN

Pregnant women (n = 13), between 180/7 and 376/7 weeks' singleton gestation, receiving sublingual buprenorphine twice daily for opioid use disorders were studied. Pharmacokinetic-2 studies were performed between 18 and 25 weeks (n = 7), pharmacokinetic-3 studies were performed between 31 and 37 weeks (n = 11), and pharmacokinetic-P was performed 4-18 weeks postpartum (n = 10). On the day of the study, blood was withdrawn prior to the daily morning dose of buprenorphine and at 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 8, and 12 hours after the dose. Buprenorphine plasma concentrations were analyzed by liquid chromatography tandem mass spectrometric detection. All pharmacokinetic parameters were observed or estimated using Microsoft Excel. Statistical analyses were performed to identify significant changes in study participants' buprenorphine pharmacokinetic parameter estimates over the duration of the study. Univariate linear and generalized linear mixed models were used to investigate changes in these measures over time, some of which were log transformed for normality.

RESULTS

Dose-normalized (plasma concentration per dose) buprenorphine plasma concentrations were significantly lower during pregnancy (pharmacokinetic-2 plus pharmacokinetic-3) than during the postpartum period (pharmacokinetic-P). Specific pharmacokinetic parameters (and level of significance) were as follows: the area under the buprenorphine plasma concentration-time curves (P < .003), maximum buprenorphine concentrations (P < .018), buprenorphine concentrations at 0 hour (P < .002), and buprenorphine concentrations at 12 hours (P < .001). None of these parameters differed significantly during pregnancy (ie, pharmacokinetic-2 vs pharmacokinetic-3). The time to maximum buprenorphine concentrations did not differ significantly between groups.

CONCLUSION

The dose-normalized plasma concentrations during a dosing interval and the overall exposure of buprenorphine (area under the buprenorphine plasma concentration-time curves) are lower throughout pregnancy compared with the postpartum period. This indicates an increase in apparent clearance of buprenorphine during pregnancy. These data suggest that pregnant women may need a higher dose of sublingual buprenorphine compared with postpartum individuals. The dose of buprenorphine should be assessed after delivery to maintain similar buprenorphine exposure during the postpartum period.

Pregnancy-Associated Changes in Pharmacokinetics: A Systematic Review

BACKGROUND

Women are commonly prescribed a variety of medications during pregnancy. As most organ systems are affected by the substantial anatomical and physiological changes that occur during pregnancy, it is expected that pharmacokinetics (PK) (absorption, distribution, metabolism, and excretion of drugs) would also be affected in ways that may necessitate changes in dosing schedules. The objective of this study was to systematically identify existing clinically relevant evidence on PK changes during pregnancy.

METHODS AND FINDINGS

Systematic searches were conducted in MEDLINE (Ovid), Embase (Ovid), Cochrane Central Register of Controlled Trials (Ovid), and Web of Science (Thomson Reuters), from database inception to August 31, 2015. An update of the search from September 1, 2015, to May 20, 2016, was performed, and relevant data were added to the present review. No language or date restrictions were applied. All publications of clinical PK studies involving a group of pregnant women with a comparison to nonpregnant participants or nonpregnant population data were eligible to be included in this review. A total of 198 studies involving 121 different medications fulfilled the inclusion criteria. In these studies, commonly investigated drug classes included antiretrovirals (54 studies), antiepileptic drugs (27 studies), antibiotics (23 studies), antimalarial drugs (22 studies), and cardiovascular drugs (17 studies). Overall, pregnancy-associated changes in PK parameters were often observed as consistent findings among many studies, particularly enhanced drug elimination and decreased exposure to total drugs (bound and unbound to plasma proteins) at a given dose. However, associated alterations in clinical responses and outcomes, or lack thereof, remain largely unknown.

CONCLUSION

This systematic review of pregnancy-associated PK changes identifies a significant gap between the accumulating knowledge of PK changes in pregnant women and our understanding of their clinical impact for both mother and fetus. It is essential for clinicians to be aware of these unique pregnancy-related changes in PK, and to critically examine their clinical implications.

Relationship Between Buprenorphine Dosing and Triglyceride Lowering and creatine kinase [corrected] Elevation in Felines: Possible Human Implications

Recently published feline data suggest that high doses of buprenorphine can elevate creatine kinase (CK) [corrected] and profoundly influence triglyceride levels in an inverted dose versus effect relationship. This intriguing observation in felines, hitherto not documented for buprenorphine, should be considered in human situations for any trends of translatability. The report evaluates the observed effects in domestic cats and what is known about buprenorphine in human subjects. Based on the objective assessment, the following are deduced: (a) although elevated CK levels is a nonissue in humans, one needs to pay attention especially when buprenorphine is used at the high end of therapeutic dose range in the presence of drugs that can impair the hepatic metabolism of buprenorphine; and (b) the potential for triglyceride lowering can be easily confirmed in human trials, and since it may occur at the relevant therapeutic doses of buprenorphine, it may be beneficial in such patients who may have added cardiovascular risk factors.

Buprenorphine for the treatment of opioid dependence in pregnancy

The treatment of opioid dependence during pregnancy has historically consisted of either medication-assisted withdrawal or maintenance treatment with methadone. Buprenorphine maintenance treatment is emerging as a treatment during pregnancy with distinct benefits for the neonate and the pregnant woman. Buprenorphine is effective in decreasing the risk of relapse in pregnant women. In addition, prenatal use of buprenorphine appears to decrease the severity and duration of neonatal abstinence syndrome as compared with methadone maintenance. Management of buprenorphine includes initiation and maintenance treatment as well as careful planning for pain control during and after delivery and prevention of postpartum relapse risk. Only very small amounts of buprenorphine enter breast milk, making it a good option for those who elect to breast-feed. There is evidence that emerging collaborative care models are effective ways to deliver buprenorphine maintenance treatment, although more investigation is needed to generalize this to the obstetric setting.

Buprenorphine and methadone for opioid addiction during pregnancy

Buprenorphine and methadone are opioid-receptor agonists used as opioid substitution therapy during pregnancy to limit exposure of the fetus to cycles of opioid withdrawal and reduce the risk of infectious comorbidities of illicit opioid use. As part of a comprehensive care plan, such therapy may result in improved access to prenatal care, reduced illicit drug use, reduced exposure to infections associated with intravenous drug use, and improved maternal nutrition and infant birth weight. This article describes differences in patient selection between the two drugs, their relative safety during pregnancy, and changes in daily doses as a guide for prescribing clinicians.

Obstetric Pharmacokinetic Dosing Studies are Urgently Needed

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

Buprenorphine use in pregnant opioid users: a critical review

Pregnancy in opioid users poses a number of problems to treating physicians. Most guidelines recommend maintenance treatment to manage opioid addiction in pregnancy, with methadone being the gold standard. More recently, buprenorphine has been discussed as an alternate medication. The use and efficacy of buprenorphine in pregnancy is still controversial. This article reviews the current database on the basis of a detailed and critical literature search performed in MEDLINE (206 counts). Most of the relevant studies (randomised clinical trials and one national cohort sample) were published in the last 2 years and mainly compared buprenorphine with methadone. Some studies are related to maternal outcomes, others to foetal, neonatal or older child outcomes. With respect to maternal outcomes, most studies suggest that buprenorphine has similar effects to methadone. Very few data from small studies discuss an effect of buprenorphine on neurodevelopment of the foetus. Neonatal abstinence syndrome is common in infants of both buprenorphine- and methadone-maintained mothers. As regards neonatal outcomes, buprenorphine has the same clinical outcome as methadone, although some newer studies suggest that it causes fewer withdrawal symptoms. Since hardly any studies have investigated the combination of buprenorphine with naloxone (which has been suggested to possibly have teratogenic effects) in pregnant women, a switch to buprenorphine monotherapy is recommended in women who become pregnant while receiving the combination product. These novel findings indicate that buprenorphine is emerging as a first-line treatment for pregnant opioid users.