Opioid agonist therapy discontinuation in British Columbia: a cross-sectional study of people who access harm reduction services

Abstract

Objectives

This study evaluates the prevalence and correlates of opioid agonist therapy (OAT) discontinuation across British Columbia (BC), using a sample of individuals who used substances and accessed harm reduction sites.

Design

This study uses data from the 2019 cross-sectional Harm Reduction Client Survey (HRCS).

Setting

The 2019 survey was administered from October to December at 22 harm reduction supply distribution sites across the 5 Regional Health Authorities of BC.

Participants

The 2019 HRCS was administered among individuals who used illicit substances in the past 6 months and were aged 19 years and above.

Primary and secondary outcome measures

The primary outcome was defined as self-reported discontinuation of OAT in the past 6 months. Measures of association (χ² and Fisher’s exact tests) and logistic regression models were used to assess the strength of association between OAT discontinuation and demographic, socioeconomic, accessibility, drug use and harm reduction correlates.

Results

Of the 194 participants included, 59.8% self-identified as cis man, 37.6% self-identified as Indigenous, 38.1% were aged 30–39 years and 43.8% had discontinued OAT in the past 6 months. Multivariable logistic regression analyses identified that those aged ≥50 years (AOR=0.12, 95% CI (0.03 to 0.45)) and those who took the survey in medium/large urban areas (AOR=0.27, 95% CI (0.07 to 0.98)) were significantly less likely to discontinue OAT, while those who experienced an overdose in the past 6 months were significantly more likely (AOR=3.77, 95% CI (1.57 to 9.03)) to have discontinued OAT in the past 6 months. Substance use, including opioids and stimulants, was similar among those who continued and discontinued OAT. Of the 73 participants who discontinued OAT and provided a reason, one-third reported discontinuing OAT because treatment was not effective, 27.4% could not get to the pharmacy during open hours, 23.3% could not make their clinic appointment and 15.1% reported challenges with transportation/travel.

Conclusions

OAT discontinuation prevention efforts for individuals using substances in BC need to address disparities in healthcare accessibility, especially in rural areas and among younger individuals. Continued access to harm reduction services can allow for safer consumption of substances for individuals enrolled in OAT programs.

Correspondence to Dr Jane A Buxton; [email protected]

Strengths and limitations of this study

• Provides insight into a unique sample of individuals with lived and living experience of substance use, who also access harm reduction services.

• Identifies factors associated with and reasons for opioid agonist therapy (OAT) discontinuation among people who have used drugs in British Columbia (BC).

• Uses cross-sectional data that prevent the establishment of temporal relationships.

• Is not representative of all people who are prescribed OAT, only those who attend harm reduction sites in the province of BC.

Introduction

Illicit drug toxicity was the leading cause of death among individuals aged 10–59 years in British Columbia (BC) from May 2022 to April 2024, which ranked as the second leading cause of potential years of life lost during this period.¹ Toxic illicit drugs have contributed to an unregulated drug poisoning emergency across North America, resulting in 2539 deaths reported in 2023 in BC alone.²

Provincial guidelines in BC recommend opioid agonist treatment (OAT) as the first-line therapy for opioid use disorder (OUD).³ Studies have demonstrated substantial reductions in opioid overdose mortality rates for those receiving OAT.⁴ However, discontinuing OAT has been identified as a high-risk period for overdose.⁵

In BC, buprenorphine/naloxone is the recommended initial treatment for patients with OUD, though methadone has been a successful medication and is at times preferred by patients.⁶ Other forms of OAT are considered when methadone and buprenorphine/naloxone are ineffective, contraindicated or not preferred.⁷ In November 2019, 22 949 individuals were dispensed OAT in BC; of them, 67.7% were dispensed methadone, 26.7% were dispensed buprenorphine/naloxone (Suboxone), 7.1% were dispensed slow-release oral morphine (Kadian) and less than 0.6% were dispensed injectable hydromorphone and diacetylmorphine (heroin) each.⁸

Individuals who use illicit substances face an elevated risk of overdose after discontinuing OAT.^{5 9} In BC, OAT retention rates have been low, with two 2020 retrospective cohort studies finding that less than 16% remain on OAT for over a year,¹⁰ with less than 40% retention rate before treatment induction, and over 50% of participants never reaching the minimum effective dose.¹¹ Factors associated with increased discontinuation among patients receiving OAT include limited access to healthcare services,¹⁰ injection drug use, incarceration in the past 12 months, recent receptive syringe or injection equipment sharing, being male,^12–14 self-identified indigeneity, younger age^{15 16} and homelessness.¹⁴

While OAT significantly reduces overdose mortality risk,⁵ individuals often continue to use illicit substances to manage medication side effects, inadequate dosing and withdrawal symptoms.¹⁷ Reported substance use patterns during OAT vary, with some Canadian studies indicating decreased use of heroin and illicit prescription opioids, but similar or increased use of powder cocaine, crack cocaine, crystal methamphetamine, cannabis and alcohol among those in OAT treatment.^{15 16 18}

This study aims to investigate OAT discontinuation prevalence and correlates among individuals using substances who access harm reduction supply distribution sites across BC. Identifying factors associated with discontinuation could inform harm reduction and help tailor treatment services.

Methods

Patient and public involvement

People with lived and living experience of substance use are involved at all stages of survey development, interpretation of findings and manuscript development. Harm Reduction Client Survey (HRCS) was developed through extensive collaboration with representative organisations, including First Nations Health Authority (FNHA) and people with lived and living experience of substance use, Vancouver Area Network of Drug Users (VANDU) and Professionals for Ethical Engagement of Peers (PEEP). This collaboration aims to ensure that questions are culturally safe and relevant and to avoid potentially triggering or stigmatising questions surrounding substance use, living circumstances or access to services. The survey is distributed in collaboration with trained staff and volunteers at each of the sites. PEEP provided input into the interpretation of study findings. Data from the survey are used to inform harm reduction planning, confirm emerging issues and evaluate as well as improve the quality of harm reduction services across the province.

Data sources

We used data from the 2019 BC HRCS which is a cross-sectional survey of eligible clients at participating harm reduction supply distribution sites who self-report having used illicit drugs in the past 6 months, are aged 19 years or older and can provide informed verbal consent. The HRCS began as a pilot in 2012 and continued annually until 2015 and then resumed in 2018 and 2019. Site selection for HRCS is based on a network that distributes supplies for safer sex and substance use as part of the provincial harm reduction program, and considers factors such as site suitability, willingness to participate, and capacity for recruitment and data collection. The HRCS is conducted under Harm Reduction Services at the BC Centre for Disease Control.

The 2019 survey was administered from October to December at 22 sites across the five Regional Health Authorities of BC.¹⁹ Trained staff and volunteers recruited participants at each site over 2 weeks. All data from the 2019 survey were managed and stored securely using the UBC’s Research Electronic Data Capture (REDCap) platform.^{20 21} Sites received $5 CAD per participant recruited and each participant received $10 CAD for participation as compensation for their time.²² Each participant provided informed verbal consent before filling out the survey. Additional details regarding data collection methods for the HRCS have been previously published.^{22 23}

Analytical sample

Participants were excluded from the analysis if they reported not using opioids, not trying to access OAT and not being prescribed OAT or preferred not to say (Survey Questions 36, 37a).²⁴ The primary outcome of interest was defined based on whether participants reported discontinuing OAT in the past 6 months (Survey Question 37b).²⁴ Figure 1 shows a flow chart illustrating how the final analytical sample was derived for the main outcome variable of OAT discontinuation.

Figure 1. Flow chart showing inclusion/exclusion criteria for determining the final analytical sample of HRCS participants.HRCS, Harm Reduction Client Survey; OAT, opioid agonist therapy.

The outcome questions were previously validated and included as part of the survey in prior years and were further modified based on consultations with on-site staff, research team members and people with lived and living experience of substance use.

Statistical analysis

Variables assessed for association with OAT discontinuation included demographics, socioeconomic status, access to services, drug use characteristics and OAT medications prescribed. For each variable, descriptive statistics were calculated and stratified by OAT discontinuation. Participants’ responses that were missing or that indicated ‘prefer not to say’ were retained but considered separately in the descriptive analyses to assess underreporting, particularly since many of the selected variables may be underreported due to the sensitive nature of the questions. A description of variables can be found in online supplemental appendix A. All variables were summarised as frequencies and proportions. P values were calculated using Pearson’s χ² or Fisher’s exact test when nonparametric testing was more appropriate, for the comparison of all categorical data.

A concept map (online supplemental appendix B) was developed using existing literature to select, link and categorise variables into separate blocks for inclusion in the multivariable models. Explanatory variables included as covariates in our final multivariable model were categorised into five groups: (1) demographic characteristics, (2) socioeconomic characteristics, (3) accessibility characteristics, (4) past 3-day drug use and (5) harms and harm reduction characteristics. For the multivariable analyses, all missing and ‘prefer not to say’ responses were grouped together as ‘unknown’. Additional response levels were combined for certain variables to increase the sample size. A description of variables can be found in online supplemental appendix C. Unadjusted ORs were calculated for all variables with newly defined levels, prior to testing for inclusion in the multivariable model (online supplemental appendix D). Stepwise covariate selection was used to determine the most parsimonious model, with model fit assessed using the Akaike Information Criterion (AIC).²⁵ The order in which the blocks and variables were added to the model was shuffled, and models were refit to confirm no effect on the final model. Variables supported by the literature with known patterns of association (ie, gender, housing status, urbanicity, stimulant use and alcohol use) were retained in the multivariable model regardless of their statistical significance or AIC value. Sensitivity analyses were conducted to ensure that this inclusion of variables did not affect the conclusions of the model (online supplemental appendix E). The explanatory merit of the model at each stage of block addition was estimated using McFadden’s likelihood ratio R².²⁶ Model fits were compared using likelihood ratio tests (LRT), with the first model (demographics block alone) compared with a null model consisting of no predictor variables and the outcome variable as the intercept.²⁷ LRTs were not used as measures to include or exclude variables, but rather as informative measures to compare models and to assess how the model changed with the addition of each block of variables. ORs, adjusted ORs (AORs) and 95% CIs are presented for the multivariable logistic regression model. All data manipulation and statistical analyses were conducted in R V.4.1.2 (1 November 2021).

Frequency distributions were used to describe the reported reasons for discontinuing OAT in the past 6 months. If a participant reported the reason as ‘other’, free-text responses were assessed using thematic analysis. Responses were categorised as either consistent with existing survey options or emerging themes that did not align with existing categories and were added to the list of possible reasons.

Results

Table 1 describes the demographics, socioeconomic, structural and accessibility characteristics of 194 study participants, 43.8% (n=85) of whom indicated that they had discontinued OAT in the past 6 months. The largest age group among participants was 30–39 years (38.1%, n=74), 59.8% (n=116) of participants identified as cis men and 37.6% (n=73) self-identified as Indigenous. Most of the sample reported being stably housed (70.1%, n=136), were experiencing unemployment (70.1%, n=136), and took the survey at sites in medium/large urban areas (70.6%, n=137). Bivariate analyses identified age as statistically significant (p<0.05) in association with OAT discontinuation, where participants aged 50 years and older had a higher proportion (82.9%) continuing OAT compared with those in other age groups.

Table 1

Demographic, socioeconomic, structural and access characteristics of included participants, stratified by continuation versus discontinuation of OAT in the past 6 months (n=194)

Characteristics	OAT status		Total (n=194) n (%)*	χ2
	Continued (n=109) n (%)†	Discontinued (n=85) n (%)†		P value‡
Gender				0.62
Cis woman§	38 (53.5%)	33 (46.5%)	71 (36.6%)
Cis man§	67 (57.8%)	49 (42.2%)	116 (59.8%)
Transgender and gender expansive¶	1 (33.3%)	2 (66.7%)	3 (1.5%)
Prefer not to say	0 (0.0%)	0 (0.0%)	0 (0.0%)
Missing	3 (75.0%)	1 (25.0%)	4 (2.1%)
Age category				<0.001**
19–29 years	17 (48.6%)	18 (51.4%)	35 (18.0%)
30–39 years	33 (44.6%)	41 (55.4%)	74 (38.1%)
40–49 years	23 (57.5%)	17 (42.5%)	40 (20.6%)
≥50 years	34 (82.9%)	7 (17.1%)	41 (21.1%)
Missing	2 (50.0%)	2 (50.0%)	4 (2.1%)
Indigenous identity††‡‡				0.33
First Nations	25 (48.1%)	27 (51.9%)	52 (26.8%)
Metis	14 (66.7%)	7 (33.3%)	21 (10.8%)
Non-Indigenous	63 (56.2%)	49 (43.8%)	112 (57.7%)
Prefer not to say	0 (0.0%)	0 (0.0%)	0 (0.0%)
Missing	7 (77.8%)	2 (22.2%)	9 (4.6%)
Stable housing§§				0.11
Yes	82 (60.3%)	54 (39.7%)	136 (70.1%)
No	27 (46.6%)	31 (53.4%)	58 (29.9%)
Prefer not to say	0 (0.0%)	0 (0.0%)	0 (0.0%)
Missing	0 (0.0%)	0 (0.0%)	0 (0.0%)
Currently employed¶¶				0.22
Yes	33 (63.5%)	19 (36.5%)	52 (26.8%)
No	73 (53.7%)	63 (46.3%)	136 (70.1%)
Prefer not to say	3 (75.0%)	1 (25.0%)	4 (2.1%)
Missing	0 (0.0%)	2 (100.0%)	2 (1.0%)
Urbanicity***				0.51
Medium/large urban	80 (58.4%)	57 (41.6%)	137 (70.6%)
Rural	9 (45.0%)	11 (55.0%)	20 (10.3%)
Small urban	20 (54.1%)	17 (45.9%)	37 (19.1%)
Health authority				1.00
Fraser Health	28 (57.1%)	21 (42.9%)	49 (25.3%)
Interior Health	25 (58.1%)	18 (41.9%)	43 (22.2%)
Island Health	16 (53.3%)	14 (46.7%)	30 (15.5%)
Northern Health	13 (56.5%)	10 (43.5%)	23 (11.9%)
Vancouver Coastal Health	27 (55.1%)	22 (44.9%)	49 (25.3%)

*Column percentages.

†Row percentages.

‡P values reflect the significance of χ² or Fisher’s exact test (where appropriate).

§A cis or cisgender person is one whose gender identity matches their sex assigned at birth.

¶Transgender and gender expansive includes people who identify as transgender men, transgender women or gender nonconforming people.

**P value significance level of ≤0.001.

††No participants who are identified as Inuit reported their OAT status.

‡‡We recognise that Indigenous identity is often a proxy for factors like intergenerational trauma, systemic racism and socioeconomic status.

§§Stable housing includes living in a private residence alone or with others, as well as other public residences such as hotels, shelters and rooming houses, and unstable housing includes not having a regular place to stay such as couch surfing, motor homes, recreational vehicle, trailers, tents, outside and street.

¶¶Current employment includes full-time employment, part-time employment and paid volunteering.

***Urbanicity of sites was derived using a classification system developed by the BC Ministry of Health specific to communities in BC, which combined definitions of urbanicity set by Statistics Canada with indicators of remoteness, population density and proximity to urban areas.⁵¹

BC, British Columbia; OAT, opioid agonist therapy.

Table 2 shows the types of drugs used in the past 3 days and the OAT medications received in the past 6 months by participants. Of the 194 participants, 57.7% (n=112) indicated being prescribed methadone in the past 6 months, 17.5% (n=34) indicated being prescribed buprenorphine/naloxone and 10.3% (n=20) reported being prescribed more than one type of OAT medication in the past 6 months. Most participants indicated some stimulant use in the past 3 days (78.9%, n=153), 69.6% (n=135) indicated crystal meth use and 20.6% (n=40) reported cocaine and/or crack use. Cannabis, tobacco and alcohol use was also commonly reported among participants at 53.6% (n=104), 85.6% (n=166) and 30.4% (n=59), respectively.

Table 2

Past 3-day drug use and OAT medication received among included participants, stratified by continuation versus discontinuation of OAT in the past 6 months (n=194)

Characteristics	OAT status		Total (n=194) n (%)*	χ2
	Continued (n=109) n (%)†	Discontinued (n=85) n (%)†		P value‡
Past 3-day methadone use				<0.01§
Yes	64 (77.1%)	19 (22.9%)	83 (42.8%)
No	11 (37.9%)	18 (62.1%)	29 (14.9%)
Missing	34 (41.5%)	48 (58.5%)	82 (42.3%)
Past 3-day buprenorphine use				0.35
Yes	8 (47.1%)	9 (52.9%)	17 (8.8%)
No	26 (50.0%)	26 (50.0%)	52 (26.8%)
Missing	75 (60.0%)	50 (40.0%)	125 (64.4%)
Past 3-day hydromorphone (Dilaudid) use				0.44
Yes	5 (55.6%)	4 (44.4%)	9 (4.6%)
No	23 (47.9%)	25 (52.1%)	48 (24.7%)
Missing	81 (59.1%)	56 (40.9%)	137 (70.6%)
Past 3-day oxycodone use				0.16
Yes	0 (0.0%)	2 (100.0%)	2 (1.0%)
No	27 (50.9%)	26 (49.1%)	53 (27.3%)
Missing	82 (59.0%)	57 (41.0%)	139 (71.6%)
Past 3-day morphine use				0.58
Yes	21 (61.8%)	13 (38.2%)	34 (17.5%)
No	21 (50.0%)	21 (50.0%)	42 (21.6%)
Missing	67 (56.8%)	51 (43.2%)	118 (60.8%)
Past 3-day any prescription opioids use				<0.01§
Yes	90 (72.0%)	35 (28.0%)	125 (64.4%)
No	3 (18.8%)	13 (81.2%)	16 (8.2%)
Missing	16 (30.2%)	37 (69.8%)	53 (27.3%)
Past 3-day heroin use				<0.01§
Yes	43 (41.7%)	60 (58.3%)	103 (53.1%)
No	10 (62.5%)	6 (37.5%)	16 (8.2%)
Missing	56 (74.7%)	19 (25.3%)	75 (38.7%)
Past 3-day fentanyl use				<0.01§
Yes	57 (47.9%)	62 (52.1%)	119 (61.3%)
No	7 (70.0%)	3 (30.0%)	10 (5.2%)
Missing	45 (69.2%)	20 (30.8%)	65 (33.5%)
Past 3-day heroin and/or fentanyl use¶				<0.01§
Yes	67 (48.6%)	71 (51.4%)	138 (71.1%)
No	4 (66.7%)	2 (33.3%)	6 (3.1%)
Missing	38 (76.0%)	12 (24.0%)	50 (25.8%)
Past 3-day any opioid use (prescribed and not prescribed)				1.00
Yes	101 (55.8%)	80 (44.2%)	181 (44.2%)
No	2 (66.7%)	1 (33.3%)	3 (1.5%)
Missing	6 (60.0%)	4 (40.0%)	10 (5.2%)
Past 3-day Xanax use				0.26
Yes	2 (28.6%)	5 (71.4%)	7 (3.6%)
No	27 (52.9%)	24 (47.1%)	51 (26.3%)
Missing	80 (58.8%)	56 (41.2%)	136 (70.1%)
Past 3-day benzodiazepines other than Xanax use				0.36
Yes	10 (47.6%)	11 (52.4%)	21 (10.8%)
No	23 (50.0%)	23 (50.0%)	46 (23.7%)
Missing	76 (59.8%)	51 (40.2%)	127 (65.5%)
Past 3-day any benzodiazepine use				0.35
Yes	12 (48.0%)	13 (52.0%)	25 (12.9%)
No	22 (50.0%)	22 (50.0%)	44 (22.7%)
Missing	75 (60.0%)	50 (40.0%)	125 (64.4%)
Past 3-day crystal meth use				0.10
Yes	69 (51.1%)	66 (48.9%)	135 (69.6%)
No	8 (66.7%)	4 (33.3%)	12 (6.2%)
Missing	32 (68.1%)	15 (31.9%)	47 (24.2%)
Past 3-day cocaine use				0.72
Yes	22 (55.0%)	18 (45.0%)	40 (20.6%)
No	21 (51.2%)	20 (48.8%)	41 (21.1%)
Missing	66 (58.4%)	47 (41.6%)	113 (58.2%)
Past 3-day crack use				0.85
Yes	21 (52.5%)	19 (47.5%)	40 (20.6%)
No	24 (55.8%)	19 (44.2%)	43 (22.2%)
Missing	64 (57.7%)	47 (42.3%)	111 (57.2%)
Past 3-day 3,4-methylenedioxymethamphetamine (MDMA) use				0.61
Yes	3 (50.0%)	3 (50.0%)	6 (3.1%)
No	28 (50.9%)	27 (49.1%)	55 (28.4%)
Missing	78 (58.6%)	55 (41.4%)	133 (68.6%)
Past 3-day other stimulants use**				0.35
Yes	9 (69.2%)	4 (30.8%)	13 (6.7%)
No	25 (49.0%)	26 (51.0%)	51 (26.3%)
Missing	75 (57.7%)	55 (42.3%)	130 (67.0%)
Past 3-day any stimulant use				0.22
Yes	82 (53.6%)	71 (46.4%)	153 (78.9%)
No	5 (83.3%)	1 (16.7%)	6 (3.1%)
Missing	22 (62.9%)	13 (37.1%)	35 (18.0%)
Past 3-day cannabis or hash use				0.25
Yes	53 (51.0%)	51 (49.0%)	104 (53.6%)
No	16 (66.7%)	8 (33.3%)	24 (12.4%)
Missing	40 (60.6%)	26 (39.4%)	66 (34.0%)
Past 3-day tobacco				0.23
Yes	91 (54.8%)	75 (45.2%)	166 (85.6%)
No	4 (44.4%)	5 (55.6%)	9 (4.6%)
Missing	14 (73.7%)	5 (26.3%)	19 (9.8%)
Past 3-day alcohol use				0.70
Yes	31 (52.5%)	28 (47.5%)	59 (30.4%)
No	25 (61.0%)	16 (39.0%)	41 (21.1%)
Missing	53 (56.4%)	41 (43.6%)	94 (48.5%)
OAT medications prescribed in the past 6/12 months				<0.01§
Methadone	67 (59.8%)	45 (40.2%)	112 (57.7%)
Buprenorphine/naloxone	15 (44.1%)	19 (55.9%)	34 (17.5%)
Slow-release oral morphine	16 (84.2%)	3 (15.8%)	19 (9.8%)
More than 1 OAT medication	4 (20.0%)	16 (80.0%)	20 (10.3%)
Missing	7 (77.8%)	2 (22.2%)	9 (4.6%)

*Column percentages.

†Row percentages.

‡P values reflect the significance of χ² or Fisher’s exact test (where appropriate).

§P value significance level of ≤0.01.

¶Heroin and fentanyl use were combined as a variable based on the knowledge that most street drugs sold as heroin contain fentanyl, and heroin use alone is uncommon.

**Stimulant use here refers to Ritalin/Adderall use.

OAT, opioid agonist therapy.

Table 3 shows descriptive statistics for the preferred mode of drug use, where 62.4% (n=121) indicated smoking/inhalation and 32.0% (n=62) indicated injection as their preferred method. Experiences of overdose in the past 6 months included 13.4% (n=26) experiencing an opioid overdose only, 4.6% (n=9) experiencing a stimulant overdose only and 4.1% (n=8) experiencing both stimulant and opioid overdose. For harm reduction variables, 57.2% (n=111) of participants indicated frequently accessing harm reduction supplies, 43.3% (n=84) indicated using overdose prevention sites (OPS) in the past 6 months and 75.8% (n=147) indicated owning a naloxone kit. Bivariate analyses identified that OAT discontinuation was significantly associated with having experienced an overdose in the past 6 months (p<0.01) and with using a supervised consumption site (SCS) in the past 6 months (p<0.05).

Table 3

Preferred mode of drug use, experiences of overdose and use of harm reduction services in the past 6 months among included participants, stratified by continuation versus discontinuation of OAT in the past 6 months (n=194)

Characteristics	OAT status		Total (n=194) n (%)*	χ2
	Continued (n=109) n (%)†	Discontinued (n=85) n (%)†		P value‡
Preferred mode of drug use				0.84
Injection	35 (56.5%)	27 (43.5%)	62 (32.0%)
Smoking/inhalation	67 (55.4%)	54 (44.6%)	121 (62.4%)
Other§	6 (66.7%)	3 (33.3%)	9 (4.6%)
Prefer not to say	0 (0.0%)	1 (100.0%)	1 (0.5%)
Missing	1 (100.0%)	0 (0.0%)	1 (0.5%)
Drug use alone¶				0.22
Yes	89 (54.3%)	75 (45.7%)	164 (84.5%)
No	19 (70.4%)	8 (29.6%)	27 (13.9%)
Prefer not to say	1 (33.3%)	2 (66.7%)	3 (1.5%)
Missing	0	0	0 (0.0%)
Experienced an overdose in the past 6 months				<0.01**
Stimulants only	3 (33.3%)	6 (66.7%)	9 (4.6%)
Opioids only	9 (34.6%)	17 (65.4%)	26 (13.4%)
Both stimulants and opioids	2 (25.0%)	6 (75.0%)	8 (4.1%)
No	91 (64.1%)	51 (35.9%)	142 (73.2%)
Don’t know	1 (50.0%)	1 (50.0%)	2 (1.0%)
Prefer not to say	0 (0.0%)	0 (0.0%)	0 (0.0%)
Missing	3 (42.9%)	4 (57.1%)	7 (3.6%)
Naloxone kit possession				0.80
Yes	84 (57.1%)	63 (42.9%)	147 (75.8%)
No	23 (53.5%)	20 (46.5%)	43 (22.2%)
Prefer not to say	0 (0.0%)	1 (100.0%)	1 (0.5%)
Missing	2 (66.7%)	1 (33.3%)	3 (1.5%)
Frequency of accessing harm reduction supplies				0.10
Frequent	56 (50.5%)	55 (49.5%)	111 (57.2%)
Occasional/never	52 (63.4%)	30 (36.6%)	82 (42.3%)
Prefer not to say	1 (100.0%)	0 (0.0%)	1 (0.5%)
Missing	0 (0.0%)	0 (0.0%)	0 (0.0%)
Used an overdose prevention site (OPS) in the past 6 months				0.01**
Yes	38 (45.2%)	46 (54.8%)	84 (43.3%)
No	70 (64.8%)	38 (35.2%)	108 (55.7%)
Prefer not to say	0 (0.0%)	0 (0.0%)	0 (0.0%)
Missing	1 (50.0%)	1 (50.0%)	2 (100.0%)

*Column percentages.

†Row percentages.

‡P values reflect the significance of χ² or Fisher’s exact test (where appropriate).

§Snorting and swallowing.

¶Refers to substance use without the presence of others.

**P value significance level of ≤0.01.

OAT, opioid agonist therapy.

Online supplemental appendix D describes the distribution and the unadjusted ORs of variables tested for inclusion in the multivariable model based on the concept map shown in online supplemental appendix B. Table 4 shows the multivariable model results after the addition of each block of variables to the model. AOR and McFadden’s pseudo-R² values are presented. The final column presents the included model, while the first column displays bivariate results and unadjusted OR values. After adjusting for other variables, the multivariable model revealed a positive association between having experienced an opioid and/or stimulant overdose in the past 6 months (relative to not having experienced an overdose) and OAT discontinuation (AOR=3.77, 95% CI (1.57 to 9.03)). Being aged ≥50 years (relative to 19–29 years old) was negatively associated with OAT discontinuation, after adjusting for other variables (AOR=0.12, 95% CI (0.03 to 0.45)). Additionally, having taken the survey in a medium/large urban area (relative to a rural community) was also negatively associated with OAT discontinuation after adjusting for other variables (AOR=0.27, 95% CI (0.07 to 0.98)). The final adjusted multivariable model (table 4) had a McFadden pseudo-R² value of 0.20, indicating moderate explanatory power.²⁶ The addition of demographic, drug use and harm reduction blocks significantly improved model fit. While the accessibility and socioeconomic blocks did not significantly contribute to model fit, they were kept for conceptual support from the literature (online supplemental appendix F).

Table 4

Estimated unadjusted ORs and adjusted ORs for correlates of OAT discontinuation among HRCS participants as determined by logistic regression

	OAT discontinuation†
	Simple bivariate	Final adjusted model
	OR (95% CI)	AOR (95% CI)‡
Demographic characteristics
Age (years)
19–29	–	–
30–39	1.17 (0.52, 2.63)	1.02 (0.39, 2.68)
40–49	0.70 (0.28, 1.74)	0.56 (0.19, 1.65)
≥50	0.19 (0.07, 0.56)**	0.12 (0.03, 0.45)**
Unknown	0.94 (0.12, 7.48)	0.97 (0.10, 9.72)
Gender
Cis man¶	–	–
Cis woman¶	1.19 (0.66, 2.15)	0.72 (0.35, 1.47)
Transgender and gender expansive††	2.73 (0.24, 31.02)	2.80 (0.20, 39.29)
Unknown	0.46 (0.05, 4.51)	1.25 (0.09, 16.87)
Socioeconomic characteristics
Stable housing‡‡
Yes	0.57 (0.31, 1.07)	1.08 (0.49, 2.36)
No	–	–
Accessibility characteristics
Urbanicity§§
Medium/large urban	0.58 (0.23, 1.50)	0.27 (0.07, 0.98)*
Small urban	0.70 (0.23, 2.07)	0.42 (0.09, 1.91)
Rural	–	–
Past 3-day drug use
Heroin and/or fentanyl¶¶
Yes	2.12 (0.38, 11.95)	0.59 (0.05, 6.63)
No	–	–
Unknown	0.63 (0.10, 3.89)	0.16 (0.01, 2.17)
Stimulants
Crystal meth	4.78 (0.54, 42.03)	8.05 (0.52, 124.60)
Other (crack, cocaine, etc, excluding crystal meth)	1.92 (0.18, 20.82)	5.52 (0.30, 100.58)
No	–	–
Unknown	2.95 (0.31, 28.14)	12.25 (0.64, 235.59)
Alcohol
Yes	1.41 (0.63, 3.17)	1.45 (0.52, 4.02)
No	---	---
Unknown	1.21 (0.57, 2.55)	1.63 (0.58, 4.58)
Harms and harm reduction characteristics
Opioid and/or stimulant overdose in the past 6 months
Yes	3.70 (1.79, 7.62)***	3.77 (1.57, 9.03)**
No	–	–
Unknown	2.23 (0.57, 8.68)	1.87 (0.42, 8.26)
OPS/SCS use in the past 6 months
Yes	2.20 (1.23, 3.94)**	1.80 (0.89, 3.65)
No	–	–
McFadden pseudo-R2		0.20

Reference categories are denoted by ‘–’.

*p<0.05, **p<0.01, ***p<0.0001.

†Final model size N=194.

‡Final model.

¶A cis or cisgender person is one whose gender identity matches their sex assigned at birth.

††Transgender and gender expansive includes people who are identified as transgender men, transgender women or gender nonconforming people.

‡‡Stable housing includes living in a private residence alone or with others as well as other public residences such as hotels, shelters and rooming houses, and unstable housing includes not having a regular place to stay.

§§Urbanicity of sites was derived using a classification system developed by the BC Ministry of Health specific to communities in BC, which combined definitions of urbanicity set by Statistics Canada with indicators of remoteness, population density and proximity to urban areas⁵¹.

¶¶Heroin and fentanyl use were combined as a variable based on the knowledge that most street drugs available as heroin contain a high percentage of fentanyl; therefore, it is difficult to ensure heroin use alone among the sample.

BC, British Columbia; HRCS, Harm Reduction Client Survey; LRT, likelihood ratio test; OAT, opioid agonist therapy.

Reported reasons for discontinuing OAT by 73 individuals are shown in Appendix G. 32.9% (n=24) stated ineffective treatment as their reason for discontinuing OAT. Access difficulties were frequently reported: 27.4% (n=20) were unable to get to the pharmacy during open hours; 23.3% (n=17) were unable to make their clinic appointment time; 15.1% (n=11) had challenges with transportation/travel and 9.6% (n=7) reported the clinic being too far away.

Discussion

Limited evidence exists on recent OAT discontinuation among people who use substances in BC, especially those seeking harm reduction services. Most studies focus on clinical trials or urban cohorts from Vancouver’s Downtown Eastside and Victoria. This study addresses this gap, examining OAT discontinuation among individuals who use substances across BC and are actively seeking harm reduction services. Our findings indicated high substance use rates among individuals on OAT in the past 6 months. Multivariable regression analyses indicated that after consideration of all variables, OAT discontinuation was positively associated with younger age, living in rural communities and experiences of opioid or stimulant overdose in the past 6 months.

In our study, individuals aged ≥50 years were 88% less likely to discontinue OAT than individuals aged 19–29 years. Youth in Canada exhibit the highest substance use disorder rates among all age groups.²⁸ Research has identified multiple risk factors contributing to elevated substance use rates among adolescents, such as brain development, peer pressure, living conditions, family dynamics and inadequate coping mechanisms for emotional stressors.^{29 30} Age has consistently been associated with retention outcomes in substance use treatment, with younger individuals typically experiencing lower retention rates.^{31 32} One of the main issues contributing to low rates of retention among youth receiving addiction treatment is the similarity of treatment regimens for adults and youth.^{31 32} The current treatment approach overlooks the diverse causes and motivations behind substance use in younger age groups.^{31 32} One way to address age-related risk factors for OAT discontinuation is by implementing youth-specific programs. Studies have shown that combining cognitive behavioural therapy with OAT can enhance treatment retention among young individuals.³² Despite recommendations in the Canadian healthcare system for psychosocial treatment alongside OAT, these recommendations are often not put into practice, leading to limited access to comprehensive care.⁷ To improve OAT retention rates for youth, it is crucial to deliver programs that offer psychosocial support tailored to individual coping strategies. These programs should complement opioid agonist medications and provide support for addressing various forms of substance use.

In our findings, accessing harm reduction services in a medium/large urban area was associated with a 0.27-fold decrease in the likelihood of discontinuing OAT in the past 6 months compared with those accessing in rural areas. We assumed that the survey location represented the participants’ residences and the location where participants accessed services. In Canada, limited funding for addiction treatment services in rural areas has led to reduced accessibility and longer wait times.³³ Moreover, rural living often leads to longer commutes for treatment, fewer available staff and concerns about stigma, confidentiality and safety,^{34 35} collectively contributing to lower access to addiction care and decreased retention rates.³⁶ Several Canadian studies have explored innovative solutions to improve addiction care accessibility in rural areas. A 2019 study in Kelowna and Kamloops, BC, assessed the use of two mobile SCS. The study found that over 90% of clients reported a positive experience but highlighted issues related to operating hours and service availability.³⁷ Another 2018 study in Ontario identified increased involvement of community pharmacists in providing medication-assisted treatment, such as methadone maintenance treatment, as a means to bridge service gaps and reduce stigma linked to rural addiction treatment clinics.³⁸ Despite these efforts, rural communities still struggle with disproportionately low access, especially to OAT. To enhance accessibility, it may be beneficial to identify rural residents and coordinate with local centres and staff to ensure appropriate service hours, representing a potential step towards improving access to addiction care in the province.

Our study revealed that individuals with opioid and/or stimulant overdose experiences in the past 6 months had a 3.77-fold higher likelihood of discontinuing OAT in the past 6 months compared with those without recent overdose incidents. However, our study’s cross-sectional nature makes it challenging to establish temporality. It is possible that those with prior overdose experiences are more prone to OAT discontinuation due to the care delivery process after an overdose event. Patients brought to the emergency room after an overdose event may be started with buprenorphine/naloxone, including a microdosing regimen.³⁹ Alternative treatment options may require outpatient clinic visits or entail longer wait times, leading some patients to discontinue treatment without proper follow-up⁴⁰; additionally, many patients may not be ready to initiate treatment at the time of hospital admission. In our study, many participants reported reasons for discontinuing OAT related to accessing their pharmacy or clinic appointments (online supplemental appendix G), leading to lower retention rates. We acknowledge that our study data are from 2019, substance use care and treatment options have since evolved, and factors like the COVID-19 pandemic and the availability of safer supply options may have influenced patients’ decisions to remain on OAT, particularly when the treatment may not be perceived as effective (online supplemental appendix G); however, insufficient dosing and lack of other support services may still impose barriers to treatment continuation. Recent studies have indicated that providing take-home doses of OAT and safer supply options can boost treatment retention rates, which was not an option at the time this survey was conducted.⁴¹ OAT discontinuation itself increases overdose risk because the effects of opioid agonists decrease, making unregulated opioids more dangerous.^{5 9} In our sample, some participants used opioids concurrently with OAT. Some physicians may discontinue OAT if urinalysis reveals nonprescribed opioid use, further elevating overdose risk. Thus, client-centred care and a collaborative approach that empowers patients to select the most appropriate care for their needs are crucial for improving treatment management and retention.

Several strategies can help identify and reduce overdose risks among individuals undergoing OAT, who continue to use substances. First, maintaining access to OPS and SCS is crucial, even for those actively engaged in OAT. In our sample, a significant portion of participants, that had continued OAT treatment, reported continued illicit substance use during treatment, with 48.6% reporting heroin and/or fentanyl use and 53.6% reporting stimulant use in the past 3 days. Discontinuing OAT can increase overdose risk due to reduced tolerance, highlighting the need for continued access to OPS/SCS. A 2021 study in Ontario, Canada found that individuals in outpatient methadone agonist therapy with shorter treatment durations faced a higher overdose risk, emphasising the importance of OPS/SCS during early treatment phases.⁴² Additionally, both emergency physicians and addiction specialists should work more closely with patients to implement a plan that works with their unique circumstances, paying particular attention to individuals with a history of overdose, OAT discontinuation, relapse and risk factors for low retention.³

Many participants in our sample reported using crystal meth, cocaine and crack in the past 3 days. Another 2019 study of HRCS participants found that over half of those who used opioids and stimulants in the past 3 days used them concurrently.¹⁷ Another study highlighted the prevalence of polysubstance use, including stimulants, among people who use opioids.⁴³ Various reasons for combining stimulants with opioids, such as self-medication, perceived reduction of overdose risk and balancing the effects of both substances.⁴⁴ Individuals with concurrent opioid and stimulant use are more likely to experience both fatal and nonfatal overdoses.^{17 45–49} Given that many of these individuals are engaged in OAT, tailored treatment services and harm reduction programmes are crucial to addressing their unique needs and reducing the elevated risk of overdose and other drug-related harms associated with concurrent opioid and stimulant use.

It is essential to recognise that OAT may not be the ultimate goal for every patient, and not every individual aims for complete abstinence. In our sample, some participants may have used OAT medications as a harm reduction strategy. The bivariate analyses showed positive associations between OPS use and OAT discontinuation in the past 6 months (table 3). This suggests important harm reduction steps taken by individuals to try and reduce risks related to substance use, particularly among those who may not have access to OAT or who may seek a safer alternative to using illicit substances. Considering the substantial number of individuals in our study who reported using illicit substances while on OAT, it is possible that OAT medications may be used as a harm reduction tool to alleviate cravings, withdrawal symptoms and the toxicity associated with illicit substance use. This issue is particularly important when positive urine tests result in OAT discontinuation by prescribers, removing the option to use OAT as a harm reduction measure.

Limitations

Our study had several limitations. First, we could not establish causality or temporality, which limited our ability to interpret findings, especially those related to overdose history and OAT discontinuation. Nonetheless, this study may serve as a foundation for future survey iterations and qualitative research with similar populations. Moreover, self-reported data introduced potential reporting bias due to social desirability and recall inaccuracy. Recall bias is likely to have primarily affected long-term questions regarding substance use in the past 6 months rather than those in the past 3 days. Meanwhile, sensitive inquiries about drug use over the past 3 days may still have been subject to reporting bias. Efforts were made to mitigate these biases by incorporating ‘missing’ or ‘prefer not to say’ responses into our analyses. Additionally, the survey’s location at harm reduction sites may have fostered a more comfortable environment for participants, reducing potential biases. However, the results may not generalise to all individuals who use substances in BC, as the HRCS primarily samples those accessing harm reduction supply distribution sites. The relatively small sample size in certain subgroups of variables may have further limited our ability to make contrasts within variables. Most individuals in our sample were actively using substances, regardless of their OAT engagement, which contrasts with some programmes that require negative urinalysis for continued treatment and may not be representative of all individuals enrolled in OAT programmes.⁵⁰

Conclusion

Our study characterised OAT discontinuation among individuals accessing harm reduction services across BC, revealing diverse personal and systemic factors that influence treatment retention. Factors such as younger age, living in rural communities and opioid or stimulant overdose were associated with an increased likelihood of OAT discontinuation. Structural interventions should address systemic issues such as unstable housing, socioeconomic stress and mental health comorbidities to offer long-term solutions for treatment discontinuation. Timely support, especially for youth, along with culturally sensitive, stigma-free harm reduction and psychosocial programmes, is crucial. Involving peers and those with lived and living experience is vital for inclusive research and policymaking, aiming to address inequities in the addiction care system.

The authors thank the survey participants for sharing their experiences through the Harm Reduction Client Survey, as well as harm reduction site coordinators and staff for their assistance with survey implementation and data collection. We also thank Professionals for Ethical Engagement of Peers (PEEP), Kurt Lock and Dr. Daniel Vigo for reviewing the manuscript and providing feedback on the interpretation of findings. The authors respectfully acknowledge that they live and work on the ancestral, traditional and unceded Indigenous territories, including the territories of the Sḵwx̱wú7mesh (Squamish), səl̓ilwətaɁɬ (Tsleil-Waututh) and xʷməθkʷəy̓əm (Musqueam) First Nations, and that the Harm Reduction Client Survey was conducted across the unceded traditional territories of over 200 First Nations.

Data availability statement

Data are available upon reasonable request.

Ethics statements

Patient consent for publication

Not applicable.

Ethics approval

This study involves human participants and has been approved by the University of British Columbia (UBC) Behavioural Research Ethics Board and other relevant local boards (H07-00570). Participants gave informed consent to participate in the study before taking part.

Footnote

Contributors KZ conducted the initial analysis, while LL, BK, MO and JAB provided data interpretation and feedback. JAB, the principal investigator, directed data interpretation and manuscript development. BG led data collection and project coordination. KP led data cleaning and dataset preparation for analysis. KZ drafted the manuscript. All authors (KZ, LL, BK, KP, BG, MO and JAB) provided constructive input, and read and approved the final manuscript before submission. JAB serves as the guarantor for the overall content.

Funding This work was supported by Health Canada’s Substance Use and Addictions Program (SUAP) (Grant #1819-HQ-000054).

Competing interests None declared.

Patient and public involvement Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.

Provenance and peer review Not commissioned; externally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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