An Exploratory Study of Sex and Gender Differences in Demographic, Psychosocial, Clinical, and Substance Use Treatment Characteristics of Patients in Outpatient Opioid Use Disorder Treatment with Buprenorphine

Validation studies and multiomics analysis of Zhx2 as a candidate quantitative trait gene underlying brain oxycodone metabolite (oxymorphone) levels and behavior

Sensitivity to the subjective reinforcing properties of opioids has a genetic component and can predict addiction liability of opioid compounds. We previously identified Zhx2 as a candidate gene underlying increased brain concentration of the oxycodone (OXY) metabolite oxymorphone (OMOR) in BALB/cJ (J) versus BALB/cByJ (By) females that could increase OXY state-dependent reward. A large structural intronic variant is associated with a robust reduction of Zhx2 expression in J mice, which we hypothesized enhances OMOR levels and OXY addiction-like behaviors. We tested this hypothesis by restoring the Zhx2 loss-of-function in J mice (mouse endogenous retroviral element knockout) and modeling the loss-of-function variant through knocking out the Zhx2 coding exon (exon 3 knockout [E3KO]) in By mice and assessing brain OXY metabolite levels and behavior. Consistent with our hypothesis, Zhx2 E3KO females showed an increase in brain OMOR levels and OXY-induced locomotor activity. However, contrary to our hypothesis, state-dependent expression of OXY conditioned place preference decreased in E3KO females and increased in E3KO males. We also overexpressed Zhx2 in the livers and brains of J mice and observed Zhx2 overexpression in select brain regions that was associated with reduced OXY state-dependent learning. Integrative transcriptomic and proteomic analysis of E3KO mice identified astrocyte function, cell adhesion, extracellular matrix properties, and endothelial cell functions as pathways influencing brain OXY metabolite concentration and behavior. These results support Zhx2 as a quantitative trait gene underlying brain OMOR concentration that is associated with changes in OXY behavior and implicate potential quantitative trait mechanisms that together inform our overall understanding of Zhx2 in brain function. SIGNIFICANCE STATEMENT: This study validated Zhx2 as a gene whose dysfunction increases brain levels of a highly potent and addictive metabolite of oxycodone, oxymorphone, in a female-specific manner. This result has broad implications for understanding the role of oxycodone metabolism and brain oxymorphone levels in the addiction liability of oxycodone (the active ingredient in OxyContin) and highlights the need for the study of sex differences in opioid metabolism as it relates to the addiction liability of opioids and opioid use disorder.

An emerging multi-omic understanding of the genetics of opioid addiction

Opioid misuse, addiction, and associated overdose deaths remain global public health crises. Despite the tremendous need for pharmacological treatments, current options are limited in number, use, and effectiveness. Fundamental leaps forward in our understanding of the biology driving opioid addiction are needed to guide development of more effective medication-assisted therapies. This Review focuses on the omics-identified biological features associated with opioid addiction. Recent GWAS have begun to identify robust genetic associations, including variants in OPRM1, FURIN, and the gene cluster SCAI/PPP6C/RABEPK. An increasing number of omics studies of postmortem human brain tissue examining biological features (e.g., histone modification and gene expression) across different brain regions have identified broad gene dysregulation associated with overdose death among opioid misusers. Drawn together by meta-analysis and multi-omic systems biology, and informed by model organism studies, key biological pathways enriched for opioid addiction-associated genes are emerging, which include specific receptors (e.g., GABAB receptors, GPCR, and Trk) linked to signaling pathways (e.g., Trk, ERK/MAPK, orexin) that are associated with synaptic plasticity and neuronal signaling. Studies leveraging the agnostic discovery power of omics and placing it within the context of functional neurobiology will propel us toward much-needed, field-changing breakthroughs, including identification of actionable targets for drug development to treat this devastating brain disease.

Predicting buprenorphine adherence among patients with opioid use disorder in primary care settings

BACKGROUND

Medications for opioid use disorder (MOUD), including buprenorphine, are effective treatments for opioid use disorder (OUD) and reduce risk for overdose and death. Buprenorphine can be prescribed in outpatient primary care settings to treat OUD; however, prior research suggests adherence to buprenorphine in these settings can be low. The purpose of this study was to identify the rates of and factors associated with buprenorphine adherence among patients with OUD in the first six months after a new start of buprenorphine.

METHODS

Data were extracted from the electronic health record (EHR) from a large integrated health system in the upper Midwest. Patients with OUD (N = 345; Mean age = 37.6 years, SD 13.2; 61.7% male; 78% White) with a new start of buprenorphine between March 2019 and July 2021 were included in the analysis. Buprenorphine adherence in the first six months was defined using medication orders; the proportion of days covered (PDC) with a standard cut-point of 80% was used to classify patients as adherent or non-adherent. Demographic (e.g., age, sex, race and ethnicity, geographic location), service (e.g., encounters, buprenorphine formulations and dosage) and clinical (e.g., diagnoses, urine toxicology screens) characteristics were examined as factors that could be related to adherence. Analyses included logistic regression with adherence group as a binary outcome.

RESULTS

Less than half of patients were classified as adherent to buprenorphine (44%). Adjusting for other factors, male sex (OR = 0.34, 95% CI = 0.20, 0.57, p < .001) and having an unexpected positive for opioids on urine toxicology (OR = 0.42, 95% CI = 0.21, 0.83, p < .014) were associated with lower likelihood of adherence to buprenorphine, whereas being a former smoker (compared to a current smoker; OR = 1.82, 95% CI = 1.02, 3.27, p = .014) was associated with greater likelihood of being adherent to buprenorphine.

CONCLUSIONS

These results suggest that buprenorphine adherence in primary care settings may be low, yet male sex and smoking status are associated with adherence rates. Future research is needed to identify the mechanisms through which these factors are associated with adherence.

Validation studies and multi-omics analysis of Zhx2 as a candidate quantitative trait gene underlying brain oxycodone metabolite (oxymorphone) levels and behavior

Sensitivity to the subjective reinforcing properties of opioids has a genetic component and can predict addiction liability of opioid compounds. We previously identified Zhx2 as a candidate gene underlying increased brain concentration of the oxycodone (OXY) metabolite oxymorphone (OMOR) in BALB/cJ (J) versus BALB/cByJ (By) females that could increase OXY state-dependent reward. A large structural intronic variant is associated with a robust reduction of Zhx2 expression in J mice, which we hypothesized enhances OMOR levels and OXY addiction-like behaviors. We tested this hypothesis by restoring the Zhx2 loss-of-function in Js (MVKO) and modeling the loss-of-function variant through knocking out the Zhx2 coding exon (E3KO) in Bys and assessing brain OXY metabolite levels and behavior. Consistent with our hypothesis, Zhx2 E3KO females showed an increase in brain OMOR levels and OXY-induced locomotor activity. However, contrary to our hypothesis, state-dependent expression of OXY-CPP was decreased in E3KO females and increased in E3KO males. We also overexpressed Zhx2 in the livers and brains of Js and observed Zhx2 overexpression in select brain regions that was associated with reduced OXY state-dependent learning. Integrative transcriptomic and proteomic analysis of E3KO mice identified astrocyte function, cell adhesion, extracellular matrix properties, and endothelial cell functions as pathways influencing brain OXY metabolite concentration and behavior. These results support Zhx2 as a quantitative trait gene underlying brain OMOR concentration that is associated with changes in OXY behavior and implicate potential quantitative trait mechanisms that together inform our overall understanding of Zhx2 in brain function.

Mitigating Sociodemographic Bias in Opioid Use Disorder Prediction: Fairness-Aware Machine Learning Framework

BACKGROUND

Opioid use disorder (OUD) is a critical public health crisis in the United States, affecting >5.5 million Americans in 2021. Machine learning has been used to predict patient risk of incident OUD. However, little is known about the fairness and bias of these predictive models.

OBJECTIVE

The aims of this study are two-fold: (1) to develop a machine learning bias mitigation algorithm for sociodemographic features and (2) to develop a fairness-aware weighted majority voting (WMV) classifier for OUD prediction.

METHODS

We used the 2020 National Survey on Drug and Health data to develop a neural network (NN) model using stochastic gradient descent (SGD; NN-SGD) and an NN model using Adam (NN-Adam) optimizers and evaluated sociodemographic bias by comparing the area under the curve values. A bias mitigation algorithm, based on equality of odds, was implemented to minimize disparities in specificity and recall. Finally, a WMV classifier was developed for fairness-aware prediction of OUD. To further analyze bias detection and mitigation, we did a 1-N matching of OUD to non-OUD cases, controlling for socioeconomic variables, and evaluated the performance of the proposed bias mitigation algorithm and WMV classifier.

RESULTS

Our bias mitigation algorithm substantially reduced bias with NN-SGD, by 21.66% for sex, 1.48% for race, and 21.04% for income, and with NN-Adam by 16.96% for sex, 8.87% for marital status, 8.45% for working condition, and 41.62% for race. The fairness-aware WMV classifier achieved a recall of 85.37% and 92.68% and an accuracy of 58.85% and 90.21% using NN-SGD and NN-Adam, respectively. The results after matching also indicated remarkable bias reduction with NN-SGD and NN-Adam, respectively, as follows: sex (0.14% vs 0.97%), marital status (12.95% vs 10.33%), working condition (14.79% vs 15.33%), race (60.13% vs 41.71%), and income (0.35% vs 2.21%). Moreover, the fairness-aware WMV classifier achieved high performance with a recall of 100% and 85.37% and an accuracy of 73.20% and 89.38% using NN-SGD and NN-Adam, respectively.

CONCLUSIONS

The application of the proposed bias mitigation algorithm shows promise in reducing sociodemographic bias, with the WMV classifier confirming bias reduction and high performance in OUD prediction.

Baseline Characteristics and Postdischarge Outcomes by Medication for Opioid Use Disorder Status Among Women with Polysubstance Use in Residential Treatment

Background

Within residential treatment, medication for opioid use disorder (MOUD) is rarely offered, so little is known about group differences by MOUD status. This study characterizes samples of women receiving and not receiving MOUD and explores postdischarge outcomes.

Methods

This is a secondary exploratory analysis of a residential clinical trial comparing women receiving treatment as usual (TAU) with those who also received computer-based training for cognitive behavioral therapy (CBT4CBT). Participants were N = 41 adult women with substance use disorder (SUD) who self-reported lifetime polysubstance use. Because 59.0% were prescribed MOUD (MOUD n = 24, no MOUD n = 17), baseline variables were compared by MOUD status; outcomes at 12 weeks postdischarge were compared by MOUD status and treatment condition using chi square and Mann-Whitney U tests.

Results

Participants were middle-aged (41.7 ± 11.6 years) and non-Latinx Black (80.4%). Most used substances in the No MOUD group were alcohol, cocaine, and cannabis, and in the MOUD group, most used substances were opioids, cannabis, and cocaine. Women in the MOUD group tended to have more severe SUD. Postdischarge substance use recurrence rates were twice as high in the MOUD group than in the No MOUD group. Among the women in the No MOUD group, those in the CBT4CBT condition increased the number of coping strategies twice as much as those receiving TAU.

Conclusion

Postdischarge substance use recurrence differed by MOUD status. CBT4CBT may be a helpful adjunct to personalized residential SUD treatment. The parent study is registered at [www.clinicaltrials.gov (ClinicalTrials.gov identifier: NCT03678051)].

Co-occurring psychiatric disorders and disparities in buprenorphine utilization in opioid use disorder: An analysis of insurance claims

Background

As the overdose crisis continues in the U.S. and Canada, opioid use disorder (OUD) treatment outcomes for people with co-occurring psychiatric disorders are not well characterized. Our objective was to examine the influence of co-occurring psychiatric disorders on buprenorphine initiation and discontinuation.

Methods

This retrospective cohort study used multi-state administrative claims data in the U.S. to evaluate rates of buprenorphine initiation (relative to psychosocial treatment without medication) in a cohort of 236,198 people with OUD entering treatment, both with and without co-occurring psychiatric disorders, grouping by psychiatric disorder subtype (mood, psychotic, and anxiety-and-related disorders). Among people initiating buprenorphine, we assessed the influence of co-occurring psychiatric disorders on buprenorphine retention. We used multivariable Poisson regression to estimate buprenorphine initiation and Cox regression to estimate time to discontinuation, adjusting for all 3 classes of co-occurring disorders simultaneously and adjusting for baseline demographic and clinical characteristics.

Results

Buprenorphine initiation occurred in 29.3 % of those with co-occurring anxiety-and-related disorders, compared to 25.9 % and 17.5 % in people with mood and psychotic disorders. Mood (adjusted-risk-ratio[aRR] = 0.82[95 % CI = 0.82-0.83]) and psychotic disorders (aRR = 0.95[0.94-0.96]) were associated with decreased initiation (versus psychosocial treatment), in contrast to greater initiation in the anxiety disorders cohort (aRR = 1.06[1.05-1.06]). We observed an increase in buprenorphine discontinuation associated with mood (adjusted-hazard-ratio[aHR] = 1.20[1.17-1.24]) and anxiety disorders (aHR = 1.12[1.09-1.14]), in contrast to no association between psychotic disorders and buprenorphine discontinuation.

Conclusions

We observed underutilization of buprenorphine among people with co-occurring mood and psychotic disorders, as well as high buprenorphine discontinuation across anxiety, mood, and psychotic disorders.

Identifying the most common barriers to opioid agonist treatment in an Australian setting

BACKGROUND

Opioid use disorder is a public health concern in Australia. Opioid agonist treatment (OAT) is effective at treating and minimising harm from opioid use disorder, yet is underused in Australia due to client barriers. Although these barriers have been reported, the barriers that are most important to clients is unclear. The aim of this paper was to determine the most important OAT barriers to Australian clients.

METHODS

A cross-sectional, self-completed survey was given to 204 opioid-dependent clients who attended needle and syringe sites in Australia. Participants were given 15 OAT barrier statements, which they answered using a 5-point Likert scale (1=strongly disagree, 2=disagree, 3=neutral, 4=agree and 5=strongly agree). The Likert scale data are presented using the count method and the mean Likert scores (for the whole sample and for subgroups).

RESULTS

The two methods determined that the four most important barriers to OAT were stigma, lack of support services, no flexibility and enjoy using opioids. Furthermore, those who used prescription opioids (compared with heroin) were female or non-binary (compared with male), were not currently using OAT (compared with current OAT), were younger (compared with older) and had high dependence scores (compared with low dependence scores) were impacted more by certain OAT barriers.

CONCLUSIONS

Policies around improving support services, reducing stigma and increasing flexibility would be beneficial to reduce barriers to OAT in Australia. Second, certain groups were more vulnerable to OAT barriers, emphasising the importance to better tailor opioid treatment programs to these specific populations to increase treatment engagement.

Development and clinical feasibility study of a brief version of an addiction-focused phenotyping battery in females receiving buprenorphine for opioid use disorder

INTRODUCTION

We aimed to streamline the NIDA Phenotyping Assessment Battery (PhAB), a package of self-report scales and neurobehavioral tasks used in substance use disorder (SUD) clinical trials, for clinical administration ease. Tailoring the PhAB to shorten administration time for a treatment setting is critical to expanding its acceptability in SUD clinical trials. This study's primary objectives were to develop a brief version of PhAB (PhAB-B) and assess its operational feasibility and acceptability in a female clinical treatment sample.

METHODS

Assessments of the original PhAB were evaluated along several criteria to identify a subset for the PhAB-B. Non-pregnant females (N=55) between ages 18-65, stabilized on buprenorphine for opioid use disorder (OUD) at an outpatient addiction clinic, completed this abbreviated battery remotely or after a provider visit in clinic. Participant satisfaction questions were administered. REDCap recorded the time to complete PhAB-B measures.

RESULTS

The PhAB-B included 11 measures that probed reward, cognition, negative emotionality, interoception, metacognition, and sleep. Participants who completed the PhAB-B (N =55) were 36.1 ± 8.9 years of age, White (54.5%), Black (34.5%), and non-Latinx (96.0%). Most participants completed the PhAB-B remotely (n = 42, 76.4%). Some participants completed it in-person (n = 13, 23.6%). PhAB-B mean completion time was 23.0 ± 12.0 min. Participant experiences were positive, and 96% of whom reported that they would participate in the study again.

CONCLUSION

Our findings support the clinical feasibility and acceptability of the PhAB-B among a female opioid use disorder outpatient addiction treatment sample. Future studies should assess the PhAB-B psychometric properties among broader treatment samples.

Current and emerging pharmacotherapies for opioid dependence treatments in adults: a comprehensive update

INTRODUCTION

Opioid use disorder (OUD) is characterized by compulsive opioid seeking and taking, intense drug craving, and intake of opioids despite negative consequences. The prevalence of OUDs has now reached an all-time high, in parallel with peak rates of fatal opioid-related overdoses, where 15 million individuals worldwide meet the criteria for OUD. Further, in 2020, 120,000 opioid-related deaths were reported worldwide with over 75,000 of those deaths occurring within the United States.

AREAS COVERED

In this review, we highlight pharmacotherapies utilized in patients with OUDs, including opioid replacement therapies, and opioid antagonists utilized for opioid overdoses and deterrent of opioid use. We also highlight newer treatments, such as those targeting the neuroimmune system, which are potential new directions for research given the recently established role of opioids in activating neuroinflammatory pathways, as well as over the counter remedies, including kratom, that may mitigate withdrawal.

EXPERT OPINION

To effectively treat OUDs, a deeper understanding of the current therapeutics being utilized, their additive effects, and the added involvement of the neuroimmune system are essential. Additionally, a complete understanding of opioid-induced neuronal alterations and therapeutics that target these abnormalities - including the neuroimmune system - is required to develop effective treatments for OUDs.

Is Illicit Substance Use Gender-Specific? The Basic Points of Mental and Health Disorders

Among the groups of users of illicit substances, a high percentage are persons deprived of their liberty; at the same time, each social and age group is also affected, to one degree or another. The purpose of this study is to provide general data on the relationship between different psychostimulants, clinical and socio-demographic studies, and gender, both among the general population and in one of the most at-risk groups. This review identifies the use of illicit substances as gender-specific in the general population. A detailed study of the causal relationship between the use of illicit substances and gender was carried out. Electronic databases Academic Search Complete, PubMed, HealthCare, Web of Science, and Google Scholar were searched for relevant studies up to 2022 associated with drug abuse and mental and health disorders. The analysis indicated that the human population showed significant differences between the sex of the consumer as to the type of drug consumers, development of addiction, and relapse. We focus on the pathological changes caused by drug use, the personal and physiological individual traits that influence drug choice, and the extent of use in one of the most affected groups of individuals. The study may provide some guidance in developing gender-specific treatment and prevention, including response to some pharmacological and behavioral therapies. The review is intended for a wide audience of social workers, toxicologists, and pharmacologists.

A Glitch in the Matrix: The Role of Extracellular Matrix Remodeling in Opioid Use Disorder

Opioid use disorder (OUD) and deaths from drug overdoses have reached unprecedented levels. Given the enormous impact of the opioid crisis on public health, a more thorough, in-depth understanding of the consequences of opioids on the brain is required to develop novel interventions and pharmacological therapeutics. In the brain, the effects of opioids are far reaching, from genes to cells, synapses, circuits, and ultimately behavior. Accumulating evidence implicates a primary role for the extracellular matrix (ECM) in opioid-induced plasticity of synapses and circuits, and the development of dependence and addiction to opioids. As a network of proteins and polysaccharides, including cell adhesion molecules, proteases, and perineuronal nets, the ECM is intimately involved in both the formation and structural support of synapses. In the human brain, recent findings support an association between altered ECM signaling and OUD, particularly within the cortical and striatal circuits involved in cognition, reward, and craving. Furthermore, the ECM signaling proteins, including matrix metalloproteinases and proteoglycans, are directly involved in opioid seeking, craving, and relapse behaviors in rodent opioid models. Both the impact of opioids on the ECM and the role of ECM signaling proteins in opioid use disorder, may, in part, depend on biological sex. Here, we highlight the current evidence supporting sex-specific roles for ECM signaling proteins in the brain and their associations with OUD. We emphasize knowledge gaps and future directions to further investigate the potential of the ECM as a therapeutic target for the treatment of OUD.

Systematic review and meta-analysis of changes in quality of life following initiation of buprenorphine for opioid use disorder

BACKGROUND

People with opioid use disorder (OUD) experience lower quality of life (QoL) than the general population, but buprenorphine treatment for OUD could help improve QoL of individuals with OUD. Thus, we conducted a systematic review and meta-analysis of the impact of buprenorphine on QoL among people with OUD.

METHODS

Seven databases were searched through August 2020. We included English-language studies with pre- and post- QoL assessments internationally. Standardized mean differences were calculated for five domains of QoL measures using a random effects model for correlated effect sizes with robust variance estimation. Meta-regression was used to assess variation in effect sizes based on QoL domain, treatment, and patient factors.

RESULTS

Twenty-one peer-reviewed studies from twelve countries were included. Only three studies included a no-treatment control group and five studies assigned groups using randomization. Improvements between baseline and follow-up were observed across all five domains of QoL measures (overall, physical, psychological, social, and environmental). The certainty of evidence was low for all domains of QoL, and very low for environmental QoL. We did not observe differences in the effect of buprenorphine on QoL by QoL domain, duration, dose, participant characteristics, or adjunctive counseling services.

CONCLUSIONS

Buprenorphine treatment likely improves overall, physical, psychological, and social QoL, and may improve environmental QoL, for individuals with OUD. Findings are limited by study quality, including lack of control groups and incomplete reporting. Future studies with more rigorous methods and comprehensive reporting are needed.

Short communication: Relationship between social determinants and opioid use disorder treatment outcomes by gender

BACKGROUND

Social determinants of health (SDoH) influence health outcomes differentially across gender. Gender differences in SDoH have been identified at baseline in opioid use disorder (OUD) treatment studies, but less is known about how SDoH and gender intersect with OUD treatment trajectories. This study aims to identify social correlates of OUD treatment outcomes from five key areas of social determinants separately for men and women receiving buprenorphine for OUD.

METHODS

This is a secondary data analysis of a cross-sectional survey with medical record review conducted with patients recruited from an office based opioid treatment clinic. Participants completed surveys between July-September 2019. A 6-month prospective medical record review was conducted to determine treatment retention, substance use recurrence, and buprenorphine continuation. Chi square, T-tests, and Mann Whitney U tested differences in social factors and OUD outcomes by gender. Gender-stratified multivariable logistic and negative binomial regressions assessed predictors of OUD outcomes.

RESULTS

Among study participants (n = 142), women were significantly younger (p < 0.001), more likely to live in a safe neighborhood (p = 0.046), and less likely to be employed (p = 0.005) or have substance use recurrence during the study period (p = 0.033) than men. For women, employment (AOR=0.19, p = 0.031) and education (AOR=0.08, p = 0.040) were negatively associated with treatment retention. For men, no social factors were associated with OUD outcomes.

CONCLUSIONS

SDoH may impact OUD treatment outcomes differently by gender. Addressing MOUD stigma and implementing patient-centered care strategies may facilitate OUD treatment continuation among employed women in recovery. Gender-related social factors should be considered in OUD treatment research.