Opioid agonist therapy (OAT) is a medical treatment for opioid use disorder, prescribed and monitored by a physician. This page explains what OAT is, the medications used, and how to get started.
Opioid agonist therapy, often shortened to OAT, is medication that treats opioid use disorder. Long-term opioid use changes how the brain responds to pain and stress, and stopping suddenly usually causes intense cravings and withdrawal. OAT uses a prescription medication that acts on the same receptors as other opioids, but in a controlled, steady way. This calms cravings and withdrawal without producing the same high, which gives your body and mind room to stabilize. It is not a quick fix — it is a medical treatment that a physician manages with you over time.
OAT is different from a short course of pills you take once and stop. Most people stay on OAT for months or years, and some stay on it long-term, because opioid use disorder is a chronic condition, similar to how diabetes or high blood pressure are managed with ongoing medication. Your dose is adjusted over time based on how you are doing, and you meet regularly with your physician to review progress. There is no fixed end date — you and your doctor decide together when, or if, tapering makes sense.
We offer three types of OAT medication: methadone, buprenorphine-naloxone, and a long-acting buprenorphine injection. Each works on the same brain receptors but differs in how it is taken, how quickly it takes effect, and how it interacts with other medications or health conditions. There is no single best option for everyone. During your assessment, the physician will ask about your opioid use history, other medications, physical and mental health, and what fits your daily life, then recommend the option that is safest and most likely to work for you.
Methadone is a full opioid agonist taken once a day, usually as a liquid. It has a long history of use in Ontario and is effective at reducing cravings and withdrawal for many people. Because the starting dose needs close monitoring, you will usually attend a pharmacy daily at first for supervised dosing, moving to take-home doses as your physician confirms it is safe. Read more on our Methadone Treatment in Toronto page for details on how the program works.
Buprenorphine-naloxone, sometimes known as Suboxone, is a partial opioid agonist with a lower risk of overdose than methadone, which often allows take-home doses sooner. A long-acting buprenorphine injection is also available for people who prefer not to take a daily pill; it is given roughly once a month once your dose is stable. Both options are explained in more detail on our Buprenorphine-Naloxone (Suboxone) Treatment and Injectable Buprenorphine Treatment pages, including who each option tends to suit.
Detox refers to the process of clearing opioids from your body, usually over several days, sometimes with medication to ease withdrawal symptoms. On its own, detox does not treat the underlying opioid use disorder — it only manages the physical withdrawal. Once the medication used during detox stops, cravings often return, and tolerance to opioids drops quickly. This means the risk of overdose is especially high in the days and weeks after detox, particularly if someone returns to using at their previous amount.
OAT takes a different approach. Instead of clearing opioids from your system and hoping cravings do not return, OAT keeps a steady, controlled level of medication in your body so cravings and withdrawal stay manageable over the long term. This lets you focus on other parts of your life — work, relationships, health — without opioid use disorder dominating your day. Many people who try detox alone relapse; OAT is generally recommended as the safer, more effective path for most people with an opioid use disorder, either instead of detox or after it.
OAT is supported by decades of clinical research and is recognized by Health Canada and the College of Physicians and Surgeons of Ontario (CPSO) as a standard, evidence-based treatment for opioid use disorder. Research consistently links OAT with a lower risk of fatal overdose, reduced illicit opioid use, and better retention in treatment compared with no medication or detox alone. It is used across Ontario in hospitals, community clinics, and family practices, not only in specialized addiction clinics.
OAT does not work the same for everyone, and it is not the only tool for recovery — many people also benefit from counselling, peer support, or treating other health conditions alongside it. Your physician will monitor how you respond, check in on side effects, and adjust your plan as needed. The goal is not just to stop opioid use, but to help you build a stable, functioning life while managing a chronic medical condition.
Your first visit starts with a conversation, not a lecture. The physician will ask about your opioid use, past treatment attempts, other medications, and physical and mental health, and will explain the OAT options in plain language. You are welcome to ask questions and share concerns, including fears about withdrawal, side effects, or what people close to you might think. Bring a list of any medications you currently take and your OHIP card if you have one; if you do not have OHIP yet, tell our staff when you book.
Once you and your physician choose a medication, you will get a prescription and instructions for your first doses, along with the name of a pharmacy that can dispense it — you can choose any pharmacy that offers OAT dispensing. Early follow-up visits are usually more frequent, often weekly, so your physician can adjust your dose and check how you are feeling. As your dose stabilizes and you and your doctor agree things are going well, visits typically become less frequent.
OAT is not something you go through alone. You will have a physician tracking your progress over time, and you can raise anything that comes up between visits, including side effects, cravings, or life stress that makes treatment harder. If at any point you want to change medications, adjust your dose, or eventually taper, that conversation happens with your physician, at your pace, based on how you are doing rather than on a fixed timeline.
Physician visits for OAT are covered by OHIP, so there is no charge to see the doctor. Medication costs depend on your insurance or drug coverage — the Ontario Drug Benefit and most private plans cover OAT medications, and staff can help you understand what applies to you. All appointments are booked in advance; we do not offer walk-in visits. Our phones are answered from 9:00 a.m. to 5:00 p.m., seven days a week, at 647-748-1337, or you can reach us at info@addictionclinictoronto.ca.
If you are in crisis right now, please do not wait for an appointment. Call ConnexOntario at 1-866-531-2600, available 24 hours a day, for confidential support and information on services near you, or call 911 if you or someone else is in immediate danger. Reaching out for help with opioid use, at any stage, is a reasonable and safe step to take.
Call 647-748-1337 or email info@addictionclinictoronto.ca to book an appointment at 55 Dundas St E, Toronto. Phones are answered 9:00 a.m. to 5:00 p.m., seven days a week.