Determinants of selection into buprenorphine/naloxone among people initiating opioid agonist treatment in British Columbia

Sex differences in comorbid pain and opioid use disorder: A scoping review

Opioid use disorder (OUD) and chronic pain are commonly co-occurring disorders which can exacerbate each other. Sex/gender differences have been shown in aspects of the clinical course and biological underpinnings of both OUD and chronic pain. The purpose of this scoping review is to summarize literature which has addressed sex/gender differences in relation to the confluence of OUD and chronic pain. This review focused on peer-reviewed journal articles with human subjects and addressing (a) opioid misuse, chronic opioid use or opioid use disorder (OUD), (b) chronic or persistent pain and (c) sex/gender differences in relation to OUD and/or chronic pain. Of the 146 papers identified by the search strategy, 30 met the criteria for inclusion. Charting focused on a priori themes of chronic pain, opioid misuse/OUD and sex/gender in sample, predictor and outcome variables, and key study findings. The majority of research identified was cross-sectional in nature, and sex/gender differences and treatment effects were largely included as post-hoc analyses. Together, the results of this early work align with higher prevalence for OUD in men/males and chronic pain in women/females, while adding critical information with respect to potential sex/gender differences in the development and treatment of their co-occurrence across a range of biological and psychosocial factors. Findings underline the importance of considering sex and gender in the intersection of the development and treatment of OUD and chronic pain.

Comparative Analysis of Instrumental Variables on the Assignment of Buprenorphine/Naloxone or Methadone for the Treatment of Opioid Use Disorder

BACKGROUND

Instrumental variable (IV) analysis provides an alternative set of identification assumptions in the presence of uncontrolled confounding when attempting to estimate causal effects. Our objective was to evaluate the suitability of measures of prescriber preference and calendar time as potential IVs to evaluate the comparative effectiveness of buprenorphine/naloxone versus methadone for treatment of opioid use disorder (OUD).

METHODS

Using linked population-level health administrative data, we constructed five IVs: prescribing preference at the individual, facility, and region levels (continuous and categorical variables), calendar time, and a binary prescriber's preference IV in analyzing the treatment assignment-treatment discontinuation association using both incident-user and prevalent-new-user designs. Using published guidelines, we assessed and compared each IV according to the four assumptions for IVs, employing both empirical assessment and content expertise. We evaluated the robustness of results using sensitivity analyses.

RESULTS

The study sample included 35,904 incident users (43.3% on buprenorphine/naloxone) initiated on opioid agonist treatment by 1585 prescribers during the study period. While all candidate IVs were strong (A1) according to conventional criteria, by expert opinion, we found no evidence against assumptions of exclusion (A2), independence (A3), monotonicity (A4a), and homogeneity (A4b) for prescribing preference-based IV. Some criteria were violated for the calendar time-based IV. We determined that preference in provider-level prescribing, measured on a continuous scale, was the most suitable IV for comparative effectiveness of buprenorphine/naloxone and methadone for the treatment of OUD.

CONCLUSIONS

Our results suggest that prescriber's preference measures are suitable IVs in comparative effectiveness studies of treatment for OUD.

Characteristics, treatment patterns and retention with extended-release subcutaneous buprenorphine for opioid use disorder: A population-based cohort study in Ontario, Canada

BACKGROUND

Uptake and retention for opioid agonist treatment (OAT) remains low. Novel extended-release formulations may improve OAT accessibility by reducing the frequency of healthcare visits. Our aim was to examine uptake, characteristics, treatment patterns and retention of individuals initiating extended-release subcutaneous buprenorphine (BUP-ER), a monthly injectable OAT.

METHODS

We conducted a population-based cohort study among adults aged 18+ initiated on BUP-ER between February 3, 2020 and March 31, 2022 in Ontario, Canada. Using administrative health data, we defined continuous BUP-ER use based on repeat injections within a 56-day period and used Kaplan-Meier curves to estimate time on treatment. Among new BUP-ER recipients, we described individual and prescriber characteristics, healthcare utilization and treatment patterns.

RESULTS

2366 individuals initiated BUP-ER. The median time to BUP-ER discontinuation was 183 days (interquartile range: 66-428 days) and 52.0% of individuals were co-prescribed buprenorphine/naloxone at least once throughout the period of BUP-ER receipt. Among individuals who initiated on a dose of 300mg BUP-ER and had three or more injections, 18.8% continued to receive only 300mg doses (N=276 of 1470). Furthermore, 28.6% of those whose dose was reduced to 100mg (N=341 of 1194) had a subsequent dose increase to 300mg.

CONCLUSIONS

On average, people initiating BUP-ER discontinue within the first 6 months of treatment. While BUP-ER is likely providing an important OAT option, the high occurrence of discontinuation, supplementation with buprenorphine/naloxone, and frequent dose increases suggest inadequacy of current dosing recommendations among a proportion of individuals.

Does opioid agonist treatment reduce overdose mortality risk in people who are older or have physical comorbidities? Cohort study using linked administrative health data in New South Wales, Australia, 2002-17

AIMS

To quantify the association between opioid agonist treatment (OAT) and overdose death by age group; test the hypothesis that across different age groups, opioid overdose mortality is lowest during OAT with buprenorphine compared with time out of treatment or OAT with methadone; and test associations between OAT and opioid overdose mortality in the presence of chronic circulatory, respiratory, liver and kidney diseases.

DESIGN

Retrospective observational cohort study using linked administrative data.

SETTING

New South Wales, Australia.

PARTICIPANTS

A total of 37 764 people prescribed OAT, 1 August 2002 and 31 December 2017.

MEASUREMENTS

OAT exposure, opioid overdose mortality and key confounders were measured using linked population data sets on OAT entry and exit, hospitalization, mental health care, incarceration and mortality. ICD-10 codes were used to define opioid overdose mortality and chronic disease groups of interest.

FINDINGS

Relative to time out of treatment, time in OAT was associated with a lower risk of opioid overdose death across all age groups and chronic diseases. Among people aged 50 years and older, there was weak evidence that buprenorphine may be associated with greater protection against opioid overdose death than methadone [generalized estimating equation (GEE) adjusted incident rate ratio (aIRR) = 0.47; 95% confidence interval (CI) = 0.21, 1.02; marginal structural models (MSM) aIRR = 0.49; 95% CI = 0.17, 1.41]. Buprenorphine was associated with greater protection against overdose death than methadone for clients with circulatory (MSM aIRR = 0.27; 95% CI = 0.11, 0.67) or respiratory (MSM aIRR = 0.26; 95% CI = 0.07, 0.94) diseases, but not liver (MSM aIRR = 0.59; 95% CI = 0.14, 2.43) or kidney (MSM aIRR = 1.16; 95% CI = 0.31, 4.36) diseases.

CONCLUSIONS

Opioid agonist treatment (OAT) appears to reduce mortality risk in people with opioid use disorder who are older or who have physical comorbidities. Opioid overdose mortality during OAT with buprenorphine appears to be lower and reduced in clients with circulatory and respiratory diseases compared with OAT with methadone.

Opioid agonist therapy switching among individuals with prescription-type opioid use disorder: Secondary analysis of a pragmatic randomized trial

BACKGROUND

Engagement and retention in opioid agonist therapy (OAT) remains a challenge. This study evaluated the impact of initial randomized OAT allocation on subsequent switching among people with prescription-type opioid use disorder (POUD).

METHODS

Secondary analysis of a 24-week Canadian multicenter, pragmatic, randomized trial conducted between 2017 and 2020 comparing flexible take-home buprenorphine/naloxone versus supervised methadone models of care for POUD. We used Cox Proportional Hazards modeling to assess for impact of treatment assignment on time to OAT switching, adjusting for important confounders. For clinical correlates, we analyzed data from baseline questionnaires on demographic, substance use, and health factors as well as urine drug screen.

RESULTS

Of 272 randomized participants, 210 initiated OAT within 14 days per trial protocol, of whom 103 participants were randomized to buprenorphine/naloxone and 107 to methadone. Within 24-week follow-up, 41 (20.5%) of all participants switched OAT with 25 (24.3%, median 27 days, 88.4 per 100 person-years) and 16 participants (15.0%, median 53.5 days, 46.1 per 100 person-years) switching from buprenorphine/naloxone and methadone arms, respectively. In adjusted analysis, allocation to buprenorphine/naloxone was associated with significantly higher risk of switching (aHR = 2.31, 95% CI 1.22 - 4.38).

CONCLUSIONS

OAT switching was common in this sample of individuals with POUD, with individuals randomly allocated to buprenorphine/naloxone being more than twice as likely to switch versus methadone. This may reflect a stepped care approach in OUD management. More research is needed to evaluate overall retention and outcomes with the different observed risks of switching between methadone and buprenorphine/naloxone.

Patient Satisfaction With Standard Methadone and Flexible Buprenorphine/Naloxone Models of Care: Results From a Pragmatic Randomized Controlled Clinical Trial

INTRODUCTION

Patient satisfaction is a critical measure of quality of care across health disciplines because it may affect clinical outcomes.

OBJECTIVES

This study aimed to examine longitudinal patient satisfaction in individuals with opioid use disorder (OUD) randomized to receive either standard methadone or flexible buprenorphine/naloxone models of care, its predictors, and association with dropout/illicit drug use.

METHODS

This study assessed patient satisfaction, using the 8-item version of the Client Satisfaction Questionnaire (CSQ), as a secondary outcome of a large phase IV pragmatic randomized controlled trial (OPTIMA). The effectiveness of standard methadone model of care was compared with flexible take-home buprenorphine/naloxone dispensation model of care in patients with prescription-type OUD. Of 272 participants recruited and followed up for 24 weeks, 183 were eligible for this study.

RESULTS

Throughout the study, patients were "satisfied" with their treatment. The average CSQ score was not significantly different between weeks 4, 12, and 24 in the total sample (χ 2 = 0.35; P = 0.84). There was no significant difference in CSQ based on treatment assignment (methadone vs flexible buprenorphine/naloxone) either overall ( z = 0.87; P = 0.38) or over time (χ 2 = 0.65; P = 0.72). High levels of depression at baseline and decreased depressive symptoms over the follow-up period predicted positive changes in patient satisfaction ( P = 0.03 and P = <0.01, respectively). Satisfaction was significantly associated with treatment retention but not illicit drug use.

CONCLUSIONS

This study demonstrates that patients with OUD on either standard methadone or flexible buprenorphine were generally satisfied with their treatment, with no difference in patient satisfaction based on treatment allocation. Given the ongoing opioid crisis, strategies to improve patient satisfaction should be further explored.

Modeling the population-level impact of opioid agonist treatment on mortality among people accessing treatment between 2001 and 2020 in New South Wales, Australia

BACKGROUND AND AIMS

The individual-level effectiveness of opioid agonist treatment (OAT) in reducing mortality is well established, but there is less evidence on population-level benefits. We use modeling informed with linked data from the OAT program in New South Wales (NSW), Australia, to estimate the impact of OAT provision in the community and prisons on mortality and the impact of eliminating excess mortality during OAT initiation/discontinuation.

DESIGN

Dynamic modeling.

SETTING AND PARTICIPANTS

A cohort of 49 359 individuals who ever received OAT in NSW from 2001 to 2018.

MEASUREMENTS

Receipt of OAT was represented through five stages: (i) first month on OAT, (ii) short (1-9 months) and (iii) longer (9+ months) duration on OAT, (iv) first month following OAT discontinuation and (v) rest of time following OAT discontinuation. Incarceration was represented as four strata: (i) never or not incarcerated in the past year, (ii) currently incarcerated, (iii) released from prison within the past month and (iv) released from prison 1-12 months ago. The model incorporated elevated mortality post-release from prison and OAT impact on reducing mortality and incarceration.

FINDINGS

Among the cohort, mortality was 0.9 per 100 person-years, OAT coverage and retention remained high (> 50%, 1.74 years/episode). During 2001-20, we estimate that OAT provision reduced overdose and other cause mortality among the cohort by 52.8% [95% credible interval (CrI) = 49.4-56.9%] and 26.6% (95% CrI =22.1-30.5%), respectively. We estimate 1.2 deaths averted and 9.7 life-years gained per 100 person-years on OAT. Prison OAT with post-release OAT-linkage accounted for 12.4% (95% CrI = 11.5-13.5%) of all deaths averted by the OAT program, primarily through preventing deaths in the first month post-release. Preventing elevated mortality during OAT initiation and discontinuation could have averted up to 1.4% (95% CrI =  0.8-2.0%) and 3.0% (95% CrI = 2.1-5.3%) of deaths, respectively.

CONCLUSION

The community and prison opioid agonist treatment program in New South Wales, Australia appears to have substantially reduced population-level overdose and all-cause mortality in the past 20 years, partially due to high retention.

Characterizing opioid agonist treatment discontinuation trends in British Columbia, Canada, 2012-2018

BACKGROUND

Given the elevated risk of mortality immediately following opioid agonist treatment (OAT) discontinuation, determining the frequency and timing of OAT discontinuation can help guide the planning of services to facilitate uninterrupted OAT. We sought to describe weekly and monthly trends in OAT episode discontinuations in British Columbia to determine the potential resource needs for implementing support services.

METHODS

This population-based retrospective study utilized a provincial-level linkage of health administrative databases to identify all people with opioid use disorder (PWOUD) who received OAT between 01/2012-08/2018. We defined OAT episodes as continuous medication dispensations without interruptions in prescribed doses lasting ≥5 days for methadone and ≥6 days for buprenorphine/naloxone. We derived the percentage of PWOUD discontinuing OAT every month and we considered weekly discontinuations between 09/2017-08/2018, accounting for weeks during which monthly income assistance payments from social service programs occurred.

RESULTS

Our study included 37,207 PWOUD discontinuing 158,027 OAT episodes. Discontinuations were relatively stable month-to-month, increasing from 10.6 % to 14.9 % (2012-2018). The monthly percentage of discontinuations was 21.2 % for buprenorphine/naloxone and 10.0 % for methadone. Weekly discontinuations were greater in income disbursement weeks (816; IQR: 752, 901) compared to other weeks (655; IQR: 615, 683; p < 0.01).

CONCLUSIONS

We identified a high, and stable rate of monthly OAT discontinuations and a consistently higher rate of discontinuing treatment among PWOUD accessing buprenorphine/naloxone. There is an urgent need to develop the evidence base for interventions to support OAT engagement and to improve clinical management of OUD to address the opioid-related overdose crisis.

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

As treatment expansion in the opioid epidemic continues, it is important to examine how the makeup of individuals with opioid use disorder (OUD) is evolving. Treatment programs are increasingly utilizing buprenorphine, an effective OUD medication. This exploratory study examines sex and gender differences in psychosocial, clinical and substance use treatment characteristics of a clinical population in outpatient medication treatment for OUD with buprenorphine. This is a secondary data analysis from a cross-sectional survey study with retrospective medical record review conducted with patients recruited from an office-based opioid treatment clinic between July-September 2019. Participants on buprenorphine for at least 28 days at time of survey completion were included (n=133). Differences between men and women were explored with Pearson χ2 and Fisher's Exact Tests for categorical variables and T-Tests for continuous variables. The sample was 55.6% women and nearly three-fourths Black (70.7%). Mean days in current treatment episode was 431.6 (SD=244.82). Women were younger and more likely to be unemployed, identify as a sexual minority, and live alone with children than men. More women than men had a psychiatric comorbidity. Women reported more prescription opioid misuse while men had more heroin only opioid use. More men reported comorbid alcohol use and a history of drug overdose. One-third of participants reported recent discrimination in a healthcare setting due to substance use. As buprenorphine-based outpatient treatment programs continue to expand, present study findings support evaluation of the unique needs of men and women in order to better tailor OUD-related services and improve treatment outcomes.

Comparative effectiveness of buprenorphine-naloxone versus methadone for treatment of opioid use disorder: a population-based observational study protocol in British Columbia, Canada

INTRODUCTION

Despite a recent meta-analysis including 31 randomised controlled trials comparing methadone and buprenorphine for the treatment of opioid use disorder, important knowledge gaps remain regarding the long-term effectiveness of different treatment modalities across individuals, including rigorously collected data on retention rates and other treatment outcomes. Evidence from real-world data represents a valuable opportunity to improve personalised treatment and patient-centred guidelines for vulnerable populations and inform strategies to reduce opioid-related mortality. Our objective is to determine the comparative effectiveness of methadone versus buprenorphine/naloxone, both overall and within key populations, in a setting where both medications are simultaneously available in office-based practices and specialised clinics.

METHODS AND ANALYSIS

We propose a retrospective cohort study of all adults living in British Columbia receiving opioid agonist treatment (OAT) with methadone or buprenorphine/naloxone between 1 January 2008 and 30 September 2018. The study will draw on seven linked population-level administrative databases. The primary outcomes include retention in OAT and all-cause mortality. We will determine the effectiveness of buprenorphine/naloxone vs methadone using intention-to-treat and per-protocol analyses-the former emulating flexible-dose trials and the latter focusing on the comparison of the two medication regimens offered at the optimal dose. Sensitivity analyses will be used to assess the robustness of results to heterogeneity in the patient population and threats to internal validity.

ETHICS AND DISSEMINATION

The protocol, cohort creation and analysis plan have been approved and classified as a quality improvement initiative exempt from ethical review (Providence Health Care Research Institute and the Simon Fraser University Office of Research Ethics). Dissemination is planned via conferences and publications, and through direct engagement and collaboration with entities that issue clinical guidelines, such as professional medical societies and public health organisations.