Evaluation of a Transitional Patient Navigation Protocol for People Living With Hepatitis C Virus in the New York City Jail System.

We evaluated outcomes from a telephone-based transitional patient navigation (TPN) service for people living with hepatitis C virus (HCV) upon returning to the community after incarceration in New York City (NYC) jails. NYC Health + Hospitals/Correctional Health Services offered referrals for TPN services provided by the NYC local health department patient navigation staff. We compared rates of connection to care among people referred for TPN services with those who were not referred. People living with HIV had a higher connection to care rate at three months (65.0% vs 39.8%, p≤.05) and people with opioid use disorder had a higher connection rate at six months (55.1% vs 36.1%, p≤.05) compared with people without these conditions. However, there was not an improved connection to HCV care associated with referral to TPN services for the overall cohort. Further research, including qualitative studies, may inform improved strategies for connection to HCV care after incarceration.

Cannabis Co-Use Among Black Individuals with Chronic Pain Who Use Opioids: Associations with Other Substance Use and Pain Related Outcomes.

Background Black individuals with chronic musculoskeletal (MSK) pain tend to experience worse pain and opioid use-related outcomes, including other substance co-use, compared with non-Hispanic White individuals. Co-using cannabis with opioids could instigate a cascade of pain-related vulnerabilities and poor outcomes. Here, we test associations between cannabis/opioid co-use and pain-related outcomes among Black individuals with chronic MSK pain. Methods Black adults with chronic MSK pain who use opioids (N=401; 51.62% female, Mage=35.90, SD=11.03) completed online measures of pain intensity/interference, emotional distress, opioid dependence, and risky use of other substances. Results Compared with opioid use alone, opioid and cannabis co-use was associated with elevated anxiety and depression symptoms, opioid dependence, and risky substance use, but not pain. Conclusions Black individuals with chronic MSK pain who co-use opioids and cannabis warrant targeted interventions that address their needs. Tailored interventions could help address disparities in pain-related outcomes and opioid morbidity and mortality rates.

Impact of the COVID-19 Pandemic on Functions of Nursing Professionals in the Care of Opioid Use Disorder: Systematic Review.

BACKGROUND: Nursing professionals are vitally involved in the cascade of care for opioid use disorders (OUDs). The global spread of COVID-19 has had complex effects on public health aspects of major diseases, including OUDs. There are limited data on the major ways in which the COVID-19 pandemic has affected the functions of nursing professionals in the care of OUDs. METHOD: This systematic review followed Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines and examined published data for trends in OUD care during the first 2 years of the COVID-19 pandemic, focusing on nursing functions. The National Library of Medicine PubMed database and the EMBASE database were examined for peer-reviewed studies with primary data published between January 1, 2020, and December 31, 2021. REVIEW FINDINGS AND CONCLUSIONS: Rapid changes were observed in numerous aspects of OUDs during the early pandemic stage, as well as its care by nursing and other health professionals. These changes include increased overdoses (primarily from synthetic opioids such as fentanyl) and emergency department visits. These trends varied considerably across U.S. jurisdictions, underscoring the importance of region-specific examinations for public health policy and intervention. Out of necessity, healthcare systems and nursing professionals adapted to the challenges of OUD care in the pandemic. These adaptations included increases in telehealth services, increases in take-home doses of methadone or buprenorphine/naloxone, and expansion of layperson training in the use of naloxone for overdose reversal. It is likely that some of these adaptations will result in long-term changes in standards of care practices for OUDs by nursing professionals.

[Sexual health in female under treatment for opiate dependence using diacetylmorphine]. / La sexualité au féminin chez les patientes traitées par diacétylmorphine.

Sexual health is a key element to the well-being and quality of life of individuals. However, it is rarely incorporated into care delivery for women with an addictive condition. Female with severe dependence to opiate have their medical and social conditions improved by diacetylmorphine treatment. Which allows them to escape situations of high-risk of sexual violence. However, this pharmacotherapy can also induce adverse effects on the sexual sphere. This paper describes the relevance of integrating psycho-socio-sexological counselling into the care provision for the opiate dependence. The counselling should be oriented to respond to the specific relational and sexual issues faced by these female patients and empowering them on their lives and in recovering a better quality of life.

La santé sexuelle constitue un élément important au bien-être et à la qualité de vie, or c'est un élément peu abordé au cours des soins des patientes souffrant de trouble addictologique. Le traitement de diacétylmorphine améliore la situation médicale et sociale des patientes souffrant d'une dépendance sévère aux opiacés et leur permet de sortir de situations à haut risque de violences sexuelles ; mais il peut également induire des effets indésirables sexuels. Cet article décrit l'importance d'intégrer à la prise en charge addictologique un accompagnement psychosocio-sexologique axé sur les difficultés sexuelles et relationnelles spécifiquement rencontrées par les patientes afin de leur offrir la possibilité de retrouver du pouvoir sur leur vie et une meilleure qualité de vie.

Posttraumatic stress disorder in people who use drugs: syringe services program utilization, treatment need, and preferences for onsite mental health care.

BACKGROUND: Syringe services programs (SSPs) are critical healthcare access points for people with opioid use disorder (OUD) who face treatment utilization barriers. Co-locating care for common psychiatric comorbidities, like posttraumatic stress disorder (PTSD), at SSPs may reduce harms and enhance the health of individuals with OUD. To guide the development of onsite psychiatric care at SSPs, we collected quantitative survey data on the prevalence of PTSD, drug use patterns, treatment experiences associated with a probable PTSD diagnosis, and attitudes regarding onsite PTSD care in a convenience sample of registered SSP clients in New York City. METHODS: Study participants were administered the PTSD Checklist for the DSM-5 (PCL-5) and asked about sociodemographic characteristics, current drug use, OUD and PTSD treatment histories, and desire for future SSP services using a structured interview. Probable PTSD diagnosis was defined as a PCL-5 score ≥ 31. RESULTS: Of the 139 participants surveyed, 138 experienced at least one potentially traumatic event and were included in the present analysis. The sample was primarily male (n = 108, 78.3%), of Hispanic or Latinx ethnicity (n = 76, 55.1%), and middle-aged (M = 45.0 years, SD = 10.6). The mean PCL-5 score was 35.2 (SD = 21.0) and 79 participants (57.2%) had a probable PTSD diagnosis. We documented frequent SSP utilization, significant unmet PTSD treatment need, and high interest in onsite PTSD treatment. CONCLUSIONS: Study findings point to the ubiquity of PTSD in people with OUD who visit SSPs, large gaps in PTSD care, and the potential for harm reduction settings like SSPs to reach people underserved by the healthcare system who have co-occurring OUD and PTSD.

A data-driven approach to implementing the HPTN 094 complex intervention INTEGRA in local communities.

BACKGROUND: HIV burden in the US among people who inject drugs (PWID) is driven by overlapping syndemic factors such as co-occurring health needs and environmental factors that synergize to produce worse health outcomes among PWID. This includes stigma, poverty, and limited healthcare access (e.g. medication to treat/prevent HIV and for opioid use disorder [MOUD]). Health services to address these complex needs, when they exist, are rarely located in proximity to each other or to the PWID who need them. Given the shifting drug use landscapes and geographic heterogeneity in the US, we evaluate a data-driven approach to guide the delivery of such services to PWID in local communities. METHODS: We used a hybrid, type I, embedded, mixed method, data-driven approach to identify and characterize viable implementation neighborhoods for the HPTN 094 complex intervention, delivering integrated MOUD and HIV treatment/prevention through a mobile unit to PWID across five US cities. Applying the PRISM framework, we triangulated geographic and observational pre-implementation phase data (epidemiological overdose and HIV surveillance data) with two years of implementation phase data (weekly ecological assessments, study protocol meetings) to characterize environmental factors that affected the viability of implementation neighborhoods over time and across diverse settings. RESULTS: Neighborhood-level drug use and geographic diversity alongside shifting socio-political factors (policing, surveillance, gentrification) differentially affected the utility of epidemiological data in identifying viable implementation neighborhoods across sites. In sites where PWID are more geographically dispersed, proximity to structural factors such as public transportation and spaces where PWID reside played a role in determining suitable implementation sites. The utility of leveraging additional data from local overdose and housing response systems to identify viable implementation neighborhoods was mixed. CONCLUSIONS: Our findings suggest that data-driven approaches provide a contextually relevant pragmatic strategy to guide the real-time implementation of integrated care models to better meet the needs of PWID and help inform the scale-up of such complex interventions. This work highlights the utility of implementation science methods that attend to the impact of local community environmental factors on the implementation of complex interventions to PWID across diverse drug use, sociopolitical, and geographic landscapes in the US. TRIAL REGISTRATION: ClincalTrials.gov, Registration Number: NCT04804072 . Registered 18 February 2021.

The misuse of codeine containing medicines: Perceptions and behaviours of qualified pharmacy professionals.

BACKGROUND:  Pharmacy professionals working in community pharmacies frequently provide pharmacist-initiated therapy, including codeine-containing medicines. Codeine is an opioid with great potential for misuse, adding to the global opioid epidemic burden. Professional pharmacy personnel are the first intervention point in relation to management of codeine use. This study highlights the importance of pharmacy professionals' perceptions and behaviours in combatting the opioid epidemic. METHODS:  A descriptive cross-sectional study was conducted. Simple random sampling included pharmacy professionals in the metropolitan city of Johannesburg. An electronic questionnaire was distributed via e-mail and data analysed descriptively. RESULTS:  Findings indicate that pharmacy personnel routinely ask patients about codeine use (n = 48; 53.9%), avoid dispensing over-the-counter (OTC) codeine as an initial treatment (n = 61; 69%) and express confidence to identify and manage codeine misuse (n = 69; 77.5%). Despite this, increased patient demands for OTC codeine (n = 69; 77.5%) were concerning, highlighting the ease of availability from internet sources (n = 76; 85.4%) and multiple pharmacies (n = 84; 94.4%). Apprehension about the lack of patient awareness on adverse health consequences (n = 66; 74.2%) and the risk of codeine dependence (n = 79; 88.8%) was expressed. CONCLUSION:  Growing concern regarding availability and accessibility of codeine-containing medicines within the community pharmacy sector is highlighted. Adverse health consequences of codeine misuse and dependence are not understood by customers and the ineffective information provided by pharmacy personnel was highlighted as a concern.Contribution: The results of this study give insight to the influence of dispensing personnel's attitude towards the growing challenges with respect to codeine containing medication abuse.

Racial and Ethnic Disparities in Geographic Availability of Buprenorphine.

OBJECTIVES: Overdose mortality has risen most rapidly among racial and ethnic minority groups while buprenorphine prescribing has increased disproportionately in predominantly non-Hispanic White urban areas. To identify whether buprenorphine availability equitably meets the needs of diverse populations, we examined the differential geographic availability of buprenorphine in areas with greater concentrations of racial and ethnic minority groups. METHODS: Using IQVIA longitudinal prescription data, IQVIA OneKey data, and Microsoft Bing Maps, we calculated 2 outcome measures across the continental United States: the number of buprenorphine prescribers per 1000 residents within a 30-minute drive of a ZIP code, and the number of buprenorphine prescriptions dispensed per capita at retail pharmacies among nearby buprenorphine prescribers. We then estimated differences in these outcomes by ZIP codes' racial and ethnic minority composition and rurality with t tests. RESULTS: Buprenorphine prescribers per 1000 residents within a 30-minute drive decreased by 3.8 prescribers per 1000 residents in urban ZIP codes (95% confidence interval = -4.9 to -2.7) and 2.6 in rural ZIP codes (95% confidence interval = -3.0 to -2.2) whose populations consisted of ≥5% racial and ethnic minority groups. There were 45% to 55% fewer prescribers in urban areas and 62% to 79% fewer prescribers in rural areas as minority composition increased. Differences in dispensed buprenorphine per capita were similar but larger in magnitude. CONCLUSIONS: Achieving more equitable buprenorphine access requires not only increasing the number of buprenorphine-prescribing clinicians; in urban areas with higher racial and ethnic minority group populations, it also requires efforts to promote greater buprenorphine prescribing among already prescribing clinicians.

The role of recovery peer navigators in retention in outpatient buprenorphine treatment: a retrospective cohort study.

BACKGROUND: Racial and ethnic disparities are evident in the accessibility of treatment for opioid use disorder (OUD). Even when medications for OUD (MOUD) are accessible, racially and ethnically minoritized groups have higher attrition rates from treatment. Existing literature has primarily identified the specific racial and ethnic groups affected by these disparities, but has not thoroughly examined interventions to address this gap. Recovery peer navigators (RPNs) have been shown to improve access and overall retention on MOUD. PATIENTS AND METHODS: In this retrospective cohort study, we evaluate the role of RPNs on patient retention in clinical care at an outpatient program in a racially and ethnically diverse urban community. Charts were reviewed of new patients seen from January 1, 2019 through December 31, 2019. Sociodemographic and clinical visit data, including which providers and services were utilized, were collected, and the primary outcome of interest was continuous retention in care. Bivariate analysis was done to test for statistically significant associations between variables by racial/ethnic group and continuous retention in care using Student's t-test or Pearson's chi-square test. Variables with p value ≤0.10 were included in a multivariable regression model. RESULTS: A total of 131 new patients were included in the study. RPNs improved continuous retention in all-group analysis (27.6% pre-RPN compared to 80.2% post-RPN). Improvements in continuous retention were observed in all racial/ethnic subgroups but were statistically significant in the non-Hispanic Black (NHB) group (p < 0.001). Among NHB, increases in continuous retention were observed post-RPN in patients with male sex (p < 0.001), public health insurance (p < 0.001), additional substance use (p < 0.001), medical comorbidities (p < 0.001), psychiatric comorbidities (p = 0.001), and unstable housing (p = 0.005). Multivariate logistic regression demonstrated that patients who lacked insurance had lower odds of continuous retention compared to patients with public insurance (aOR = 0.17, 95% CI 0.039-0.70, p = 0.015). CONCLUSIONS: RPNs can improve clinical retention for patients with OUD, particularly for individuals experiencing several sociodemographic and clinical factors that are typically correlated with discontinuation of care.

Recovery peer navigators improve continuous clinical retention following initiation of outpatient treatment for opioid use disorder.Recovery peer navigators may be especially beneficial for patients with factors and identifiers commonly associated with discontinuation of care.

A master regulator of opioid reward in the ventral prefrontal cortex.

In addition to their intrinsic rewarding properties, opioids can also evoke aversive reactions that protect against misuse. Cellular mechanisms that govern the interplay between opioid reward and aversion are poorly understood. We used whole-brain activity mapping in mice to show that neurons in the dorsal peduncular nucleus (DPn) are highly responsive to the opioid oxycodone. Connectomic profiling revealed that DPn neurons innervate the parabrachial nucleus (PBn). Spatial and single-nuclei transcriptomics resolved a population of PBn-projecting pyramidal neurons in the DPn that express µ-opioid receptors (µORs). Disrupting µOR signaling in the DPn switched oxycodone from rewarding to aversive and exacerbated the severity of opioid withdrawal. These findings identify the DPn as a key substrate for the abuse liability of opioids.

"If it wasn't for them, I don't think I would be here": experiences of the first year of a safer supply program during the dual public health emergencies of COVID-19 and the drug toxicity crisis.

BACKGROUND: In response to the devastating drug toxicity crisis in Canada driven by an unregulated opioid supply predominantly composed of fentanyl and analogues, safer supply programs have been introduced. These programs provide people using street-acquired opioids with prescribed, pharmaceutical opioids. We use six core components of safer supply programs identified by people who use drugs to explore participant perspectives on the first year of operations of a safer supply program in Victoria, BC, during the dual public health emergencies of COVID-19 and the drug toxicity crisis to examine whether the program met drug-user defined elements of an effective safer supply model. METHODS: This study used a community-based participatory research approach to ensure that the research was reflective of community concerns and priorities, rather than being extractive. We interviewed 16 safer supply program participants between December 2020 and June 2021. Analysis was structured using the six core components of effective safer supply from the perspective of people who use drugs, generated through a prior study. RESULTS: Ensuring access to the 'right dose and right drugs' of medications was crucial, with many participants reporting success with the available pharmaceutical options. However, others highlighted issues with the strength of the available medications and the lack of options for smokeable medications. Accessing the safer supply program allowed participants to reduce their use of drugs from unregulated markets and manage withdrawal, pain and cravings. On components related to program operations, participants reported receiving compassionate care, and that accessing the safer supply program was a non-stigmatizing experience. They also reported receiving support to find housing, access food, obtain ID, and other needs. However, participants worried about long term program sustainability. CONCLUSIONS: Participants in the safer supply program overwhelmingly appreciated it and felt it was lifesaving, and unlike other healthcare or treatment services they had previously accessed. Participants raised concerns that unless a wider variety of medications and ability to consume them by multiple routes of administration became available, safer supply programs would remain unable to completely replace substances from unregulated markets.

Multi-task transfer learning for the prediction of entity modifiers in clinical text: application to opioid use disorder case detection.

BACKGROUND: The semantics of entities extracted from a clinical text can be dramatically altered by modifiers, including entity negation, uncertainty, conditionality, severity, and subject. Existing models for determining modifiers of clinical entities involve regular expression or features weights that are trained independently for each modifier. METHODS: We develop and evaluate a multi-task transformer architecture design where modifiers are learned and predicted jointly using the publicly available SemEval 2015 Task 14 corpus and a new Opioid Use Disorder (OUD) data set that contains modifiers shared with SemEval as well as novel modifiers specific for OUD. We evaluate the effectiveness of our multi-task learning approach versus previously published systems and assess the feasibility of transfer learning for clinical entity modifiers when only a portion of clinical modifiers are shared. RESULTS: Our approach achieved state-of-the-art results on the ShARe corpus from SemEval 2015 Task 14, showing an increase of 1.1% on weighted accuracy, 1.7% on unweighted accuracy, and 10% on micro F1 scores. CONCLUSIONS: We show that learned weights from our shared model can be effectively transferred to a new partially matched data set, validating the use of transfer learning for clinical text modifiers.

Low-dose overlap initiation with split tablets of buprenorphine in intubated intensive care unit patients with opioid use disorder.

BACKGROUND: As the opioid public health crisis evolves to include fentanyl and other potent synthetic opioids, more patients are admitted to the hospital with serious complications of drug use and frequently require higher levels of care, including intensive care unit (ICU) admission, for acute and chronic conditions related to opioid use disorder (OUD). This patient population poses a unique challenge when managing sedation and ensuring adequate ventilation while intubated given their high opioid requirements. Starting a patient on medications such as buprenorphine may be difficult for inpatient providers unfamiliar with its use, which may lead to undertreatment of patients with OUD, prolonged mechanical ventilation and length of stay. METHODS: We developed a 7-day buprenorphine low dose overlap initiation (LDOI) schedule for patients with OUD admitted to the ICU (Table 1). Buprenorphine tablets were split by pharmacists and placed into pre-made blister packs as a kit to be loaded into the automated medication dispensing machine for nursing to administer daily. An internal quality review validated the appropriate dosing of split-dose tablets. To simplify order entry and increase prescriber comfort with this new protocol, we generated an order set within our electronic health record software with prebuilt buprenorphine titration orders. This protocol was implemented alongside patient and healthcare team education and counseling on the LDOI process, with follow-up offered to all patients upon discharge. RESULTS: Here we report a series of 6 ICU patients started on buprenorphine using the LDOI schedule with split buprenorphine tablets. None of the 6 patients experienced precipitated withdrawal upon buprenorphine initiation using the LDOI schedule, and 5/6 patients were successfully extubated during the buprenorphine initiation. Four of six patients had a decrease in daily morphine milligram equivalents, with 3 patients transitioning to buprenorphine alone. CONCLUSION: Initiating buprenorphine via LDOI was found to be successful in the development of a protocol for critically ill patients with OUD. We examined LDOI of buprenorphine in intubated ICU patients and found no events of acute precipitated withdrawal. This protocol can be used as a guide for other institutions seeking to start critically ill patients on medication treatment for OUD during ICU admission.

Feasibility of Web-Based Single-Session Empowered Relief in Patients With Chronic Pain Taking Methadone or Buprenorphine: Protocol for a Single-Arm Trial.

BACKGROUND: Chronic pain affects tens of millions of US adults and continues to rise in prevalence. Nonpharmacologic behavioral pain treatments are greatly needed and yet are often inaccessible, particularly in settings where medication prescribing is prioritized. OBJECTIVE: This study aims to test the feasibility of a live-instructor, web-based 1-session pain relief skills class in an underserved and potentially at-risk population: people with chronic pain prescribed methadone or buprenorphine either solely for pain or for comorbid opioid use disorder (OUD). METHODS: This is a national, prospective, single-arm, uncontrolled feasibility trial. The trial is untethered from medical care; to enhance participants' willingness to join the study, no medical records or drug-monitoring records are accessed. At least 45 participants will be recruited from outpatient pain clinics and from an existing research database of individuals who have chronic pain and are taking methadone or buprenorphine. Patient-reported measures will be collected at 6 time points (baseline, immediately post treatment, 2 weeks, and months 1-3) via a web-based platform, paper, or phone formats to include individuals with limited internet or computer access and low literacy skills. At baseline, participants complete demographic questions and 13 study measures (Treatment Expectations, Body Pain Map, Medication Use, Pain Catastrophizing Scale [PCS], Patient-Reported Outcomes Measurement Information System [PROMIS] Measures, and Opioid Craving Scale). Immediately post treatment, a treatment satisfaction and acceptability measure is administered on a 0 (very dissatisfied) to 10 (completely satisfied) scale, with 3 of these items being the primary outcome (perceived usefulness, participant satisfaction, and likelihood of using the skills). At each remaining time point, the participants complete all study measures minus treatment expectations and satisfaction. Participants who do not have current OUD will be assessed for historical OUD, with presence of OUD (yes or no), and history of OUD (yes or no) reported separately. Feasibility threshold is set as an overall group treatment satisfaction rating of 8 of 10. In-depth qualitative interviews will be conducted with about 10 participants to obtain additional data on patient perceptions, satisfactions, needs, and wants. To assess preliminary efficacy, we will examine changes in pain catastrophizing, pain intensity, pain bothersomeness, sleep disturbance, pain interference, depression, anxiety, physical function, global impression of change, and opioid craving at 1 month post treatment. RESULTS: This project opened to enrollment in September 2021 and completed the recruitment in October 2023. The data collection was completed in February 2024. Results are expected to be published in late 2024. CONCLUSIONS: Results from this trial will inform the feasibility and preliminary efficacy of Empowered Relief in this population and will inform the design of a future randomized controlled trial testing web-based Empowered Relief in chronic pain and comorbid OUD. TRIAL REGISTRATION: ClinicalTrials.gov NCT05057988; https://clinicaltrials.gov/study/NCT05057988. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/53784.

Vaccines as Immunotherapies for Substance Use Disorders.

Substance use disorders (SUD) present a worldwide challenge with few effective therapies except for the relative efficacy of opioid pharmacotherapies, despite limited treatment access. However, the proliferation of illicit fentanyl use initiated a dramatic and cascading epidemic of lethal overdoses. This rise in fentanyl overdoses regenerated an interest in vaccine immunotherapy, which, despite an optimistic start in animal models over the past 50 years, yielded disappointing results in human clinical trials of vaccines against nicotine, stimulants (cocaine and methamphetamine), and opioids. After a brief review of clinical and selected preclinical vaccine studies, the "lessons learned" from the previous vaccine clinical trials are summarized, and then the newest challenge of a vaccine against fentanyl and its analogs is explored. Animal studies have made significant advances in vaccine technology for SUD treatment over the past 50 years, and the resulting anti-fentanyl vaccines show remarkable promise for ending this epidemic of fentanyl deaths.

Harm Reduction for Opioid Use Disorder: Strategies and Outcome Metrics.

Tweet: The authors discuss harm reduction strategies and associated outcome metrics in relation to the ongoing opioid crisis.

Transcriptional signatures of fentanyl use in the mouse ventral tegmental area.

Synthetic opioids such as fentanyl contribute to the vast majority of opioid-related overdose deaths, but fentanyl use remains broadly understudied. Like other substances with misuse potential, opioids cause lasting molecular adaptations to brain reward circuits, including neurons in the ventral tegmental area (VTA). The VTA contains numerous cell types that play diverse roles in opioid use and relapse; however, it is unknown how fentanyl experience alters the transcriptional landscape in specific subtypes. Here, we performed single nuclei RNA sequencing to study transcriptional programs in fentanyl-experienced mice. Male and female C57/BL6 mice self-administered intravenous fentanyl (1.5 µg/kg/infusion) or saline for 10 days. After 24 h abstinence, VTA nuclei were isolated and prepared for sequencing on the 10× platform. We identified different patterns of gene expression across cell types. In dopamine neurons, we found enrichment of genes involved in growth hormone signalling. In dopamine-glutamate-GABA combinatorial neurons, and some GABA neurons, we found enrichment of genes involved in Pi3k-Akt signalling. In glutamate neurons, we found enrichment of genes involved in cholinergic signalling. We identified transcriptional regulators for the differentially expressed genes in each neuron cluster, including downregulated transcriptional repressor Bcl6, and upregulated transcription factor Tcf4. We also compared the fentanyl-induced gene expression changes identified in mouse VTA with a published rat dataset in bulk VTA, and found overlap in genes related to GABAergic signalling and extracellular matrix interaction. Together, we provide a comprehensive picture of how fentanyl self-administration alters the transcriptional landscape of the mouse VTA that serves as the foundation for future mechanistic studies.