What is opioid agonist therapy?

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Opioid agonist therapy (OAT) is an evidence-based treatment approach. By preventing withdrawal and cravings, OAT can help people who want to reduce or stop using opioids. It can also support people to reduce harms related to the criminalization of drug use, supporting their health and well-being. 

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This article explains what OAT is, discusses challenges with availability and retention and highlights the importance of harm reduction and other services to supporting the health of individuals receiving OAT and helping them to achieve their goals.

Opioid agonist therapy (OAT) medications

OAT is an approach that involves taking long-acting medications recommended by Canadian guidelines for the treatment of opioid use disorder (OUD).1,2 There are three categories of OAT medications available in Canada:1,3–5

Oral OAT: Buprenorphine/naloxone (brand name Suboxone), methadone (brand names include Methadose, Metadol-D), and slow-release oral morphine (SROM; brand name Kadian). These medications are typically taken orally once a day. 

Extended-release OAT: Extended-release buprenorphine (brand name Sublocade). This medication is administered once a month by a healthcare provider, injected under the skin.6To start this medication, it is recommended that people be on a stable dose of oral buprenorphine/naloxone first.

Injectable OAT (iOAT): Injectable hydromorphone or diacetylmorphine (prescription heroin). These medications are self-administered within specialized clinics, usually up to three times a day.4 Access to iOAT is very limited in Canada.7,8

Prescribed alternatives (also known as safer supply) are another approach that may be available for some people at risk of drug toxicity. This approach involves providing short-acting opioids (e.g., hydromorphone tablets) as an alternative to unregulated substances, with the primary goal of reducing drug toxicity and other harms associated with unregulated drugs.9OAT medications such as methadone or SROM may be provided alongside prescribed alternatives to help prevent withdrawal.9 

What does the evidence say about OAT?

Evidence shows that OAT is more effective than other treatment approaches (e.g., counselling, stand-alone withdrawal management or detox, residential treatment without OAT) at:2

  • reducing opioid use
  • improving retention in treatment
  • reducing risk of overdose 

In addition, research suggests that OAT reduces harms and can support people’s health. OAT is associated with: 

  • reduced risk of all-cause mortality10
  • reduced sharing of injection supplies and reduced risk of hepatitis C and HIV transmission11,12
  • improved HIV treatment outcomes among people living with HIV13
  • reduced risk of skin and soft-tissue infections14 

Taken together, the evidence demonstrates that OAT is an effective approach that can help people who want to reduce their opioid use to achieve this goal, as well as reducing harms and supporting people’s health. 

Considerations for OAT prescribing

OAT may be provided in a number of different settings, including through primary care, community-based clinics, residential treatment centres, hospitals and prisons. Canadian guidelines suggest that OAT should be viewed as a long-term, open-ended treatment — meaning that it should continue for as long as the individual wants and be responsive to their goals and circumstances.5 Long-term relationships between providers and individuals receiving OAT can enable providers to develop trust with individuals, address other health issues and provide referrals to other services.1 

There are a number of factors to consider regarding which OAT medication(s) are prescribed for an individual, including:3,5 

  • the individual’s preferences and goals (e.g., whether they want to continue using unregulated opioids or other drugs, or reduce or stop their use)
  • the individual’s life circumstances (e.g., whether they can safely store medications at home, whether they can visit a pharmacy daily)
  • the individual’s previous experience with treatment (e.g., whether they have found one medication works better than another for them)
  • the prescriber’s professional background, experience and capacity 

Each OAT medication option has advantages and disadvantages (e.g., the time it takes to reach an adequate dose, the frequency of pharmacy or clinic visits, the risk of adverse events or side effects).1,3,5 Providers should explain these considerations to patients to help them come to a collaborative decision about which medication(s) may be best.1,3,5

Different medications may be better suited to different people at different times. People may choose to change medications to see what works best for them.1,3,5

What are the standards of care for people receiving OAT? 

The standards of care for people receiving OAT are multifaceted.1 Canadian guidelines recommend that people receiving OAT have access to a range of related services and supports, including the following:1,3,5

Harm reduction services: People receiving OAT should be regularly offered information about and referrals to harm reduction services, such as harm reduction supplies, safer drug use education, naloxone kits, overdose prevention education, and supervised consumption services (SCS).1,5

Psychosocial treatment: People receiving OAT should be offered psychosocial treatment (i.e., different types of counselling, motivational interviewing, contingency management).1,5 Psychosocial treatments can improve retention in OAT, which is associated with improved health outcomes.1 However, guidelines state that people should not be required to engage in these services to access OAT.1,5

People receiving OAT may also be offered psychosocial supports (i.e., social services and supports that can improve quality of life such as family services, housing, income assistance), both through multidisciplinary care teams (e.g., social workers, health navigators, peer support workers) and through referrals to other services where possible.1,3,5

Canadian guidelines state that people receiving OAT are entitled to certain standards of care.1 These standards of care include a person-centred approach that respects each person’s: 1

  • rights (e.g., to be involved in decisions about their care, to provide informed consent)
  • preferences (e.g., to treatment type and duration)
  • dignity (e.g., to be treated as a unique human being and to not be stigmatized and discriminated against)
  • experience (e.g., to receive treatment with a level of accessibility, flexibility and intensity that is appropriate given their goals, priorities, and life circumstances)1

Many of these standards of care are consistent with harm reduction principles.15 In fact, integrating harm reduction principles into treatment settings and processes can help ensure holistic care, improve the quality of life of the individual on OAT, and strengthen the relationship between the individual and the healthcare provider.3,5

What are the challenges with availability and retention?

It can be challenging for individuals to access OAT. Oral OAT is not equally accessible in every province and territory16,17 and there can be further barriers for people who live in rural and remote communities.17,18 While all physicians and some other healthcare providers can prescribe oral OAT (e.g., trained registered and psychiatric nurses in some provinces can prescribe buprenorphine/naloxone),17,19 many do not.20,21 Extended-release OAT is available only in some provinces and territories; however, its uptake is increasing, particularly in rural regions.22 Injectable OAT is available only in a handful of specialized clinics in cities across the country.7,8 

Evidence indicates that people who are on OAT for longer are more likely to experience improved health outcomes.1 However, estimates indicate that less than half of people who start OAT stay on it for more than six months and retention on OAT appears to decline over time.23,24 In some regions, the median time that people stay on some types of OAT is just five weeks.25 Several factors contribute to retention challenges: 

  • Strict program requirements such as daily pharmacy visits for oral OAT can create logistical burdens, especially for people with work and childcare responsibilities, unstable housing, or mobility or transportation challenges.24,26,27
  • Changes to the unregulated drug supply and drug use patterns (e.g., addition of sedatives to unregulated opioids, increased co-use of stimulants and opioids) may also impact OAT retention in various ways.28–30
  • Standard doses may not prevent withdrawal and cravings among people who use fentanyl, which can lead to disengagement from OAT.31–33
  • Stigma and discrimination from healthcare providers can create barriers. People report feeling judged or shamed when accessing OAT prescriptions, and the clinical practices of some providers, such as urine drug screening practices, can feel punitive.24,34

There can be additional barriers for individuals and communities who face structural inequities and/or compounded stigma related to substance use. These groups include people who live in rural and remote communities,18,35 people experiencing homelessness or housing insecurity,26 racialized people,36 Indigenous people,37 youth38 and people who are pregnant or parenting.39 

Framing opioid use and treatment in context

Canadian guidelines recommend OAT as effective, evidence-based treatment for people with a diagnosis of opioid use disorder (OUD).1,2 This medical framing implies that people who experience challenges with opioids have a disorder or a disease.1,2 Advocates for this medical framing argue that it reduces stigma by emphasizing that people with OUD deserve access to the same standards of care as those with other chronic health conditions.1,40,41 However, evidence suggests that this framing has not reduced stigma or improved care for people diagnosed with OUD.40,42 Furthermore, when challenges and harms that people experience with opioids are seen as primarily being associated with a medical disorder, underlying social and structural factors can be ignored.40,43 This can lead to approaches that seek to support individuals’ substance use goals without attending to broader circumstances in their lives. 

Complex interactions of individual, social and structural factors affect opioid use. Factors such as early childhood experiences, poverty, housing, gender, racism, colonialism and criminalization shape people’s lives, their substance use, their risk of harms and their decisions about OAT.40,43–46 Keeping this context in mind is important — OAT is seen by some people not as treatment for a disorder but as a way to reduce the risk of harms related to criminalization (e.g., as it reduces the need to purchase illegal opioids, which can expose people to overdose, arrest and other harms).47 Addressing criminalization and other social and structural factors that drive harms requires more than medications and medical treatments; it requires comprehensive, person-centred programs and changes to policies and systems.

Implications for service providers

Service providers can play an important role in supporting people to make decisions around OAT. It is critical that service providers recognize the complexity of opioid use and avoid making assumptions about what is best for an individual or judgments about their decisions. Service providers can provide support, help people to navigate barriers, and advocate for their needs, regardless of their goals.

Support that service providers can offer to people who want or are considering OAT:

  • They can provide education about different options. This includes being aware of the different OAT medications and the types of programs available locally (e.g., whether OAT providers work from a low-threshold approach or have a goal of abstinence). 
  • They can be prepared to provide referrals to OAT. This may include local or telehealth services. 
  • They can support individuals to consider what their goals are and help them to advocate for those goals with their healthcare provider.
  • They can support individuals to address barriers to starting OAT. 
  • They can support individuals to stay safe while waiting to start OAT. This includes providing access to harm reduction services such as harm reduction supplies, naloxone and overdose prevention services. 

Support that service providers can offer to people receiving OAT:

  • They can ensure that people are offered harm reduction education, supplies and naloxone and are aware of the harm reduction services (e.g., SCS) available locally. 
  • They can provide referrals to psychosocial treatments (e.g., counselling), if the individual is interested. 
  • They can provide referrals to appropriate psychosocial supports (e.g., housing, income), if the individual is interested. 
  • They can talk to the individual about what is working and what is not. Different OAT medications work better for different people. It may take time to find the right dose, and some people may try switching medications to see what works best for them.3
  • They can support people to address barriers related to staying on treatment. This may include support with transportation to a pharmacy or clinic, support with requirements to access take-home doses (e.g., safe medication storage) or support navigating relationships or challenges with others involved in their treatment (e.g., healthcare providers, pharmacists). 
  • They can advocate for continuity of care for the individual. If an individual starts OAT in one setting (e.g., community, residential treatment, prison, hospital), efforts may be necessary to ensure they maintain access to OAT if they move to another setting.1

Support that service providers can offer to people receiving OAT and wanting to stop treatment:

  • They can provide non-judgmental reminders that stopping OAT will cause their opioid tolerance to decrease quickly, which increases the risk of overdose if they use opioids. They can remind the individual about key overdose prevention strategies (e.g., not using alone, having naloxone available) and available harm reduction services (e.g., SCS) if they use drugs after discontinuing OAT.
  • They can support the individual to develop a plan for managing cravings and reducing harms associated with unregulated opioids after treatment. Individuals who want to stop taking OAT may wish to discuss options (e.g., a slow taper off of OAT, medications to help manage cravings) with their healthcare provider.
  • They can provide referrals to other available services, based on the individual’s goals. This may include other treatment programs, harm reduction services, and/or prescribed alternatives programs, if available.

Additional resources:

Addiction Treatment in Context: Principles for a System of Just, Accessible, and Voluntary Care – Canadian Drug Policy Coalition 

CATIE statement on safer supply – CATIE

CATIE statement on the need for a spectrum of substance use services – CATIE

References

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Externally reviewed by: Dr. Ahmed Bayoumi and Alex Rooyakkers

Production of this article has been made possible through a financial contribution from Health Canada's Substance Use and Addictions Program. The views expressed herein do not necessarily represent the views of Health Canada.

About the author(s)

Magnus Nowell is CATIE’s knowledge specialist in harm reduction. Magnus has previously worked in harm reduction research, community organizing and housing. He has a master’s degree in health promotion.