Provider costs of treating opioid dependence with extended-release buprenorphine in Australia.

INTRODUCTION: The costs of providing medication-assisted treatment for opioid dependence can determine its scale of provision. To provide estimates of the costs of extended-release buprenorphine (BUP-XR), we performed a bottom-up costing analysis of provider operational treatment costs. METHODS: Data were collected in a single-arm open label trial of BUP-XR injections conducted in specialist public drug treatment services and primary care private practices in three Australian states (the CoLAB study). The unit costs of resources used for each activity were combined with quantities used at each participating facility to arrive at the average annual cost per client. RESULTS: One hundred participants across the six health facility sites received monthly subcutaneous BUP-XR injections administered by a health-care practitioner. The average cost of providing 1 year of treatment per participant was $6656 ($6026-$8326). Screening cost (initial assessment and medical history) was $282 while monthly follow-up appointments cost $531 per client. The main cost driver was the monthly treatment costs accounting for 79% of the average annual client cost, with medication costs comprising 95% of this cost. DISCUSSION AND CONCLUSION: With medication costs making up the largest proportion of treatment costs, treatment using BUP-XR has the potential to free up other health system resources, for example, staff time. The costs reported in this study can be used in an economic evaluation to estimate the net benefit or cost-effectiveness of BUP-XR especially when compared to other opioid agonist treatments.

Hepatitis C treatment outcome among people in prison: The SToP-C study.

BACKGROUND AND AIMS: Hepatitis C virus (HCV) burden is higher among people in prison given high prevalence of injecting drug use. This study evaluated direct-acting antiviral (DAA) treatment outcome in prisons. METHODS: The Surveillance and Treatment of Prisoners with hepatitis C (SToP-C) study enrolled individuals incarcerated in four Australian prisons (2017-2019). Participants with detectable HCV RNA were offered sofosbuvir-velpatasvir for 12 weeks. Sustained virological response (SVR) was assessed in intention-to-treat (ITT; participants commencing treatment and due for SVR assessment before study close) and per-protocol (PP; participants with documented treatment completion and SVR assessment) populations. RESULTS: Among 799 participants with HCV, 324 (41%) commenced treatment (94% male; median age, 32 years; median duration of incarceration, 9 months). In ITT population (n = 310), 201 had documented treatment completion (65% [95% CI: 59-70]), and 137 achieved SVR (ITT-SVR: 44% [95% CI: 39-50]). In PP population (n = 143), 137 achieved SVR (PP-SVR: 96% [95% CI: 91-98]). Six participants had quantifiable HCV RNA at SVR assessment from treatment failure (n = 2) or reinfection (n = 4). Release or inter-prison transfer was common reasons for no documented treatment completion (n = 106/109 [97%]) and no SVR assessment (n = 57/58 [98%]). In ITT analysis, longer incarceration was associated with increased SVR (adjusted OR per month 1.03 [95% CI: 1.01-1.04]). CONCLUSION: Among participants who completed DAA treatment and were assessed for SVR, treatment outcome was consistent with non-prison clinical studies. However, most individuals did not complete treatment or lacked study-documented treatment outcome due to release or transfer. Strategies to accommodate dynamic prisoner populations are required to ensure continuity of HCV care, including treatment completion and post-treatment care.

Development of an evidence-based hepatitis C education program to enhance public health literacy in the Australian prison sector: The Hepatitis in Prisons Education program (HepPEd).

BACKGROUND: Australia's prisons have a high chronic hepatitis C (HCV) prevalence (8 %). Antiviral therapies and prison-based hepatitis services are available, but only a minority of those eligible are being treated. Improving the HCV public health literacy of the prison sector via targeted education may overcome key barriers to scale-up treatment. This paper describes the: i) HCV public health literacy of the prison setting; ii) barriers and solutions for HCV education and service engagement; iii) HCV education program co-design and development processes; and iv) HepPEd resources. METHODS: A national needs assessment was conducted to analyse the HCV public health literacy of the target audience groups in the prisons (healthcare providers; custodial officers; people in prison) to inform development of a prison-specific HCV education program (HepPEd). Structured interviews were conducted with key informants (n = 40). Three National Steering Committees, one for each target group, were convened to co-design and develop HepPEd. RESULTS: Only healthcare providers involved with hepatitis care were considered to have 'good' to 'very good' HCV health literacy (including knowledge, attitudes, and capabilities), with all other groups considered less favourably. Key barriers identified included being time poor (healthcare providers), poor motivation (custodial officers) and stigma (people in prison). Peer education delivery was considered a key facilitator for custodial officers and people in prison. A suite of multi-modal resources addressing the perceived gaps in HCV health literacy was developed, with a broad theme of 'Let's talk about hep C'. Delivery of HepPEd was designed to overcome key barriers and utilise facilitators for each group. CONCLUSIONS: Significant gaps in HCV health literacy were perceived amongst the target audience groups. The comprehensive co-design and development processes utilised in HepPEd suggest the program will be well-placed to improve the HCV public health literacy of the prison sector and thereby enhance HCV testing and treatment rates amongst people in prison.

A phase 3 randomised double-blind placebo-controlled trial of mirtazapine as a pharmacotherapy for methamphetamine use disorder: a study protocol for the Tina Trial.

BACKGROUND: There are no approved pharmacotherapies for methamphetamine use disorder. Two preliminary phase 2 randomised controlled trials have found mirtazapine, a tetracyclic antidepressant, to be effective in reducing methamphetamine use. The proposed Tina Trial is the first phase 3 placebo-controlled randomised trial to examine the effectiveness and safety of mirtazapine as an outpatient pharmacotherapy for methamphetamine use disorder. METHODS: This is a multi-site phase 3 randomised, double-blind, placebo-controlled parallel trial. Participants are randomly allocated (1:1) to receive either mirtazapine (30 mg/day for 12 weeks) or matched placebo, delivered as a take-home medication. The target population is 340 people aged 18-65 years who have moderate to severe methamphetamine use disorder. The trial is being conducted through outpatient alcohol and other drug treatment clinics in Australia. The primary outcome is measured as self-reported days of methamphetamine use in the past 4 weeks at week 12. Secondary outcomes are methamphetamine-negative oral fluid samples, depressive symptoms, sleep quality, HIV risk behaviour and quality of life. Other outcomes include safety (adverse events), tolerability, and health service use. Medication adherence is being monitored using MEMS® Smart Caps fitted to medication bottles. DISCUSSION: This trial will provide information on the safety and effectiveness of mirtazapine as a pharmacotherapy for methamphetamine use disorder when delivered as an outpatient medication in routine clinical practice. If found to be safe and effective, this trial will support an application for methamphetamine use disorder to be included as a therapeutic indication for the prescription of mirtazapine. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry ACTRN12622000235707. Registered on February 9, 2022.

96-week retention in treatment with extended-release subcutaneous buprenorphine depot injections among people with opioid dependence: Extended follow-up after a single-arm trial.

BACKGROUND: The most recent formulation of buprenorphine treatment is extended-release depot injections (BUP-XR) that are administered subcutaneously by health care professionals. This study aimed to observe treatment outcomes of BUP-XR delivered in standard practice during a 96-week follow-up period in a community setting. METHODS: This study is an extension of the CoLAB study, a prospective single-arm, multicentre, open label trial (N=100, 7 sites in Australia) among people with opioid dependence who received monthly injections of BUP-XR to evaluate the retention in treatment. Participants were followed for 96 weeks, comprising 48 weeks of the CoLAB study followed by a 48-week extension. RESULTS: Of 100 participants at baseline, 47 were retained on BUP-XR at 96 weeks. The median time retained on monthly depot was 90 weeks. Heroin use (adjusted OR=0.19, P=0.012) in the month prior to baseline was associated with lower odds of retention on BUP-XR. Older age at first opioid use (adjusted OR= 1.08, P=0.009) and longer duration in OAT at baseline (adjusted OR= 1.12, P=0.001) were associated with increased retention. Prevalence of past four-weeks opioid use was estimated at 4% at 96 weeks of treatment (prevalence 0.04, 95%CI: 0.00-0.11) compared to 15% at baseline. Quality of life and medication treatment satisfaction improved over time for those retained in treatment. CONCLUSION: This is one of the few studies to describe long term (96 week) retention in treatment with BUP-XR in a community setting. It displayed retention rates with 47% of participants completing 96 weeks of treatment with BUP-XR. Patient reported outcomes suggest improvements in client wellbeing. FUNDING: Indivior.

Incidence of hepatitis C virus infection in the prison setting: The SToP-C study.

People in prison are at high risk of HCV given high injecting drug use prevalence. This study evaluated HCV incidence and associated injecting drug use characteristics in prison. The SToP-C study enrolled people incarcerated in four Australian prisons. Participants were tested for HCV at enrolment and then every 3-6 months (October-2014 to November-2019). Participants eligible for this analysis included those at-risk of HCV primary infection (anti-HCV negative) or re-infection (anti-HCV positive, HCV RNA negative) with follow-up assessment. A total of 1643 eligible participants were included in analyses (82% male; median age 33 years; 30% injected drugs in prison; 1818 person-years of follow-up). Overall HCV incidence was 6.11/100 person-years (95%CI: 5.07-7.35), with higher rate of re-infection (9.34/100 person-years; 95%CI: 7.15-12.19) than primary infection (4.60/100 person-years; 95%CI: 3.56-5.96). In total population (n = 1643), HCV risk was significantly higher among participants injecting drugs in prison [vs. no injecting; adjusted hazard ratio (aHR): 10.55, 95%CI: 5.88-18.92), and those who were released and re-incarcerated during follow-up (vs. remained incarcerated; aHR: 1.60, 95%CI: 1.03-2.49). Among participants who injected recently (during past month, n = 321), HCV risk was reduced among those receiving high-dosage opioid agonist therapy (OAT), i.e. methadone ≥60 mg/day or buprenorphine ≥16 mg/day, (vs. no OAT, aHR: 0.11, 95%CI: 0.02-0.80) and increased among those sharing needles/syringes without consistent use of disinfectant to clean injecting equipment (vs. no sharing, HR: 4.60, 95%CI: 1.35-15.66). This study demonstrated high HCV transmission risk in prison, particularly among people injecting drugs. High-dosage OAT was protective, but improved OAT coverage and needle/syringe programmes to reduce sharing injecting equipment are required.

A 'one-stop-shop' point-of-care hepatitis C RNA testing intervention to enhance treatment uptake in a reception prison: The PIVOT study.

BACKGROUND & AIMS: Prisons are key venues for scaling-up hepatitis C virus (HCV) testing and treatment. Complex clinical pathways and frequent movements of people in prison remain barriers to HCV care. This study evaluated the impact of a 'one-stop-shop' point-of-care HCV RNA testing intervention on treatment uptake compared with standard of care among people recently incarcerated in Australia. METHODS: PIVOT was a prospective, non-concurrent, controlled study comparing HCV treatment uptake during 'standard of care' (n = 239; November 2019-May 2020) and a 'one-stop-shop' intervention (n = 301; June 2020-April 2021) in one reception prison in Australia. The primary endpoint was uptake of direct-acting antiviral treatment at 12 weeks from enrolment. Secondary outcomes included the time taken from enrolment to each stage in the care cascade. RESULTS: A total of 540 male participants were enrolled. Median age (29 vs. 28 years) and history of injecting drug use (48% vs. 42%) were similar between standard of care and intervention phases. Among people diagnosed with current HCV infection (n = 18/63 in the standard of care phase vs. n = 30/298 in the intervention phase), the proportion initiating direct-acting antiviral treatment within 12 weeks from enrolment in the intervention phase was higher (93% [95% CI 0.78-0.99] vs. 22% [95% CI 0.64-0.48]; p <0.001), and the median time to treatment initiation was shorter (6 days [IQR 5-7] vs. 99 days [IQR 57-127]; p <0.001) compared to standard of care. CONCLUSIONS: The 'one-stop-shop' intervention enhanced treatment uptake and reduced time to treatment initiation among people recently incarcerated in Australia, thereby overcoming key barriers to treatment scale-up in the prison sector. IMPACT AND IMPLICATIONS: This study provides important insights for policymakers regarding optimal HCV testing and treatment pathways for people newly incarcerated in prisons. The findings will improve health outcomes in people in prison with chronic HCV infection by increasing testing and treatment, thereby reducing infections, liver-related morbidity/mortality, and comorbidities. The findings will change clinical practice, clinical guidelines, and international guidance, and will inform future research and national and regional strategies, in particular regarding point-of-care testing, which is being rapidly scaled-up in various settings globally. The economic impact will likely include health budget savings resulting from reduced negative health outcomes relating to HCV, and health system efficiencies resulting from the introduction of simplified models of care. CLINICAL TRIALS REGISTRATION: This study is registered at Clinicaltrials.gov (NCT04809246).

Can a new formulation of opiate agonist treatment alter stigma?: Place, time and things in the experience of extended-release buprenorphine depot.

INTRODUCTION: Stigma has corrosive effects on all aspects of care and can undermine individual and population health outcomes. Addiction-related stigma has implications for opiate agonist treatment (OAT) and the people who receive, provide and fund it. It is important to understand how stigma is made in OAT and the political purposes that it serves, in order to change the relations of stigma and avoid the reproduction of stigma in the delivery of new treatment formulations, such as extended release buprenorphine (BUP-XR). METHODS: Semi-structured qualitative interviews were conducted at two time points with participants in a prospective single-arm, multicentre, open-label trial of monthly BUP-XR. Thirty-six participants (25 men, 11 women) were interviewed, and of these 32 participated in a second interview to explore their experience of transition from other treatment to BUP-XR. RESULTS: Participants were highly aware of the of the social and material effects of stigma through the negative stereotypes attached to OAT and those who receive it. Participants narrated examples of how stigma governed as a biopower in the relations and practices of OAT provision at numerous levels: structural (such as in public discourse about OAT and the people who receive it, in media, in perceptions about the decisions of investment in medical technologies); organisational (policies about legitimate access to OAT); interpersonal (with health workers) and individual (self-identities). BUP-XR allowed greater freedom and normalcy for clients. The experience of BUP-XR drew attention to the stigmatising potential of time, place and things associated with other OAT requiring daily (or frequent) dosing, accentuating how stigma comes to be materialised as a relational effect of everyday practices. CONCLUSIONS: Receiving BUP-XR allowed participants to avoid some of the everyday biopolitical powers of other forms of OAT and to reshape self-identities. The altering of relations between time, place and things associated with other forms of OAT allowed participants to feel as though they "pass as normal" . However, the negative public discourse and stigma of OAT is a potential threat to BUP-XR to realise its potential for individual and population benefits.

Hepatitis C Virus Reinfection Following Direct-Acting Antiviral Treatment in the Prison Setting: The SToP-C Study.

BACKGROUND: Injection drug use (IDU) following treatment for hepatitis C virus (HCV) infection may lead to reinfection, particularly if access to harm reduction services is suboptimal. This study assessed HCV reinfection risk following direct-acting antiviral therapy within Australian prisons that had opioid agonist therapy (OAT) programs but did not have needle and syringe programs (NSPs). METHODS: The Surveillance and Treatment of Prisoners With Hepatitis C (SToP-C) study enrolled people incarcerated in 4 prisons between 2014 and 2019. Participants treated for HCV were followed every 3-6 months to identify reinfection (confirmed by sequencing). Reinfection incidence and associated factors were evaluated. RESULTS: Among 388 participants receiving treatment, 161 had available posttreatment follow-up and were included in analysis (92% male; median age, 33 years; 67% IDU in prison; median follow-up 9 months). Among those with recent (in the past month) IDU (n = 71), 90% had receptive needle/syringe sharing. During 145 person-years (PY) of follow-up, 18 cases of reinfection were identified. Reinfection incidence was 12.5/100 PY (95% confidence interval [CI]: 7.9-19.8) overall, increasing to 28.7/100 PY (95% CI: 16.3-50.6) among those with recent IDU and needle/syringe sharing. In adjusted analysis, recent IDU with needle/syringe sharing was associated with increased reinfection risk (adjusted hazard ratio [aHR], 4.74 [95% CI: 1.33-16.80]; P = .016) and longer HCV testing interval with decreased risk (ie, chance of detection; aHR, 0.41 per each month increase [95% CI: .26-.64]; P < .001). CONCLUSIONS: A high rate of HCV reinfection was observed within prison. Posttreatment surveillance and retreatment are -essential to limit the impact of reinfection. High-coverage OAT and NSPs should be considered within prisons. CLINICAL TRIALS REGISTRATION: NCT02064049.

Outcomes of a single-arm implementation trial of extended-release subcutaneous buprenorphine depot injections in people with opioid dependence.

BACKGROUND: Opioid agonist treatment (OAT) is an effective intervention for opioid dependence. Extended-release buprenorphine injections (BUP-XR) may have additional potential benefits over sublingual buprenorphine. This single-arm trial evaluated outcomes among people receiving 48 weeks of BUP-XR in diverse community healthcare settings in Australia, permitting examination of outcomes when BUP-XR is delivered in standard practice. METHODS: Participants were recruited from a network of specialist public drug treatment services, primary care and some private practices in three states. Following a minimum 7 days on 8-32 mg of sublingual buprenorphine (±naloxone), participants received monthly subcutaneous BUP-XR injections administered by a healthcare practitioner and completed monthly research interviews. The primary endpoint was retention in treatment at 48 weeks. FINDINGS: Participants (n = 100) were 28% women, mean age 44 years with a long history of OAT (median 5.8 years); heroin was the most common opioid of concern (58%). Treatment retention at 24 and 48 weeks was 86% and 75%, respectively. Participants with past-month injecting drug use (OR 0.23; 95%CI: 0.09-0.61) or heroin use (OR 0.23; 95%CI: 0.08-0.65) at baseline had lower odds of being retained in treatment to 48 weeks. Reductions in multiple forms of extra-medical drug use were observed. Improvements in quality of life, participation in employment, and treatment satisfaction measures were also observed. INTERPRETATION: This real-world implementation study of BUP-XR demonstrated high retention and treatment satisfaction. This study provides important additional data on the uptake and experience of clients, with relevance for policy makers, health service planners, administrators, and practitioners. FUNDING: Indivior. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT03809143.

Evaluating the Prevention Benefit of HCV Treatment: Modeling the SToP-C Treatment as Prevention Study in Prisons.

BACKGROUND AND AIMS: Between 2014 and 2019, the SToP-C trial observed a halving in HCV incidence in four Australian prisons following scale-up of direct-acting antiviral (DAA) therapy. However, the contribution of HCV treatment to this decline is unclear because the study did not have a control group. We used modeling to consider this question. APPROACH AND RESULTS: We parameterized and calibrated a dynamic model of HCV transmission in prisons to data from each SToP-C prison on incarceration dynamics, injecting drug use, HCV prevalence trends among prison entrants, baseline HCV incidence before treatment scale-up, and subsequent HCV treatment scale-up. The model projected the decrease in HCV incidence resulting from increases in HCV treatment and other effects. We assessed whether the model agreed better with observed reductions in HCV incidence overall and by prison if we included HCV treatment scale-up, and its prevention benefits, or did not. The model estimated how much of the observed decrease in HCV incidence was attributable to HCV treatment in prison. The model projected a decrease in HCV incidence of 48.5% (95% uncertainty interval [UI], 41.9-54.1) following treatment scale-up across the four prisons, agreeing with the observed HCV incidence decrease (47.6%; 95% CI, 23.4-64.2) from the SToP-C trial. Without any in-prison HCV treatment, the model indicated that incidence would have decreased by 7.2% (95% UI, -0.3 to 13.6). This suggests that 85.1% (95% UI, 72.6-100.6) of the observed halving in incidence was from HCV treatment scale-up, with the remainder from observed decreases in HCV prevalence among prison entrants (14.9%; 95% UI, -0.6 to 27.4). CONCLUSIONS: Our results demonstrate the prevention benefits of scaling up HCV treatment in prison settings. Prison-based DAA scale-up should be an important component of HCV elimination strategies.

Evaluation of hepatitis C treatment-as-prevention within Australian prisons (SToP-C): a prospective cohort study.

BACKGROUND: Limited empirical evidence exists for the effectiveness of hepatitis C virus (HCV) treatment-as-prevention. The Surveillance and Treatment of Prisoners with hepatitis C (SToP-C) study aimed to assess the effect of HCV treatment-as-prevention in the prison setting. METHODS: SToP-C was a prospective study, including a before-and-after analysis, within a cohort of people incarcerated in two maximum-security prisons (male) and two medium-security prisons (one male, one female) in New South Wales, Australia. All prison inmates aged at least 18 years were eligible for enrolment. After HCV testing, participants were monitored for risk behaviours and HCV infection, among three sub-populations: uninfected (HCV antibody-negative); previously infected (HCV antibody-positive, HCV RNA-negative); and infected (HCV antibody and HCV RNA-positive). Uninfected participants were followed up every 3-6 months to detect HCV primary infection and previously infected participants were followed up every 3-6 months to detect re-infection. Participants with HCV infection were assessed for treatment, initially standard-of-care treatment (administered by prison health services) from 2014 to mid-2017, then direct-acting antiviral (DAA) treatment scale-up from mid-2017 onwards (12 weeks of sofosbuvir plus velpatasvir, administered through SToP-C). Participants were followed up until study closure in November, 2019. The primary study outcome was HCV incidence before and after DAA treatment scale-up among participants at risk of HCV primary infection or re-infection. This study is registered with ClinicalTrials.gov, NCT02064049. FINDINGS: Between Oct 30, 2014, and Sept 30, 2019, 3691 participants were enrolled in the SToP-C study. 719 (19%) participants had detectable HCV RNA, 2240 (61%) were at risk of primary HCV infection, and 725 (20%) were at risk of re-infection at baseline. DAA treatment was initiated in 349 (70%) of 499 eligible participants during the treatment scale-up period. The HCV incidence analysis comprised 1643 participants at risk of HCV infection or re-infection during longitudinal follow-up (median age 33 years [IQR 27-42]; 1350 [82%] male). 487 (30%) of 1643 participants reported injecting drugs in prison. HCV incidence decreased from 8·31 per 100 person-years in the pre-treatment scale-up period to 4·35 per 100 person-years in the post-treatment scale-up period (incidence rate ratio [IRR] 0·52 [95% CI 0·36-0·78]; p=0·0007). The incidence of primary infection decreased from 6·64 per 100 person-years in the pre-treatment scale-up period to 2·85 per 100 person-years in the post-treatment scale-up period (IRR 0·43 [95% CI 0·25-0·74]; p=0·0019), whereas the incidence of re-infection decreased from 12·36 per 100 person-years to 7·27 per 100 person-years (0·59 [0·35-1·00]; p=0·050). Among participants reporting injecting drugs during their current imprisonment, the incidence of primary infection decreased from 39·08 per 100 person-years in the pre-treatment scale-up period to 14·03 per 100 person-years in the post-treatment scale-up period (IRR 0·36 [95% CI 0·16-0·80]; p=0·0091), and the incidence of re-infection decreased from 15·26 per 100 person-years to 9·34 per 100 person-years (0·61 [0·34-1·09]; p=0·093). The adjusted analysis (adjusted for age, Indigenous Australian ethnicity, duration of stay in prison, previous imprisonment, injecting drug use status, and prison site) indicated a significant reduction in the risk of HCV infection between the pre-DAA treatment scale-up and post-DAA treatment scale-up periods (adjusted hazard ratio 0·50 [95% CI 0·33-0·76]; p=0·0014). INTERPRETATION: DAA treatment scale-up was associated with reduced HCV incidence in prison, indicative of a beneficial effect of HCV treatment-as-prevention in this setting. These findings support broad DAA treatment scale-up within incarcerated populations. FUNDING: Australian National Health and Medical Research Council Partnership Project Grant and Gilead Sciences.

Open-label, multicentre, single-arm trial of monthly injections of depot buprenorphine in people with opioid dependence: protocol for the CoLAB study.

INTRODUCTION: Opioid agonist treatment is effective for opioid dependence and newer extended-release buprenorphine (BUP-XR) injections represent a significant development. The Community Long-Acting Buprenorphine (CoLAB) study aims to evaluate client outcomes among people with opioid dependence receiving 48 weeks of BUP-XR treatment, and examines the implementation of BUP-XR in diverse community healthcare settings in Australia. METHODS AND ANALYSIS: The CoLAB study is a prospective single-arm, multicentre, open-label trial of monthly BUP-XR injections in people with opioid dependence. Participants are being recruited from a network of general practitioner and specialist drug treatment services located in the states of New South Wales, Victoria and South Australia in Australia. Following a minimum 7 days on 8-32 mg of sublingual buprenorphine (±naloxone), participants will receive monthly subcutaneous BUP-XR injections administered by a healthcare practitioner at intervals of 28 days (-2/+14 days). The primary endpoint is participant retention in treatment at 48 weeks after treatment initiation. Secondary endpoints will evaluate dosing schedule variations, craving, withdrawal, substance use, health and well-being, and client-reported treatment experience. Qualitative and costing substudies will examine implementation barriers and facilitators at the client and provider level. ETHICS AND DISSEMINATION: The study has received ethics approval from the St Vincent's Hospital Sydney Human Research Ethics Committee (Ref. HREC/18/SVH/221). The findings will be disseminated via publication in peer-reviewed journals, presentations at national and international scientific conferences, and in relevant community organisation publications and forums. TRIAL REGISTRATION NUMBER: NCT03809143 PROTOCOL IDENTIFIER: CoLAB1801, V.4.0 dated 01 August 2019.