What Is Fentanyl?
Fentanyl is a synthetic opioid used in medicine to treat severe pain, and it is at the centre of Canada’s overdose crisis. It is strong. A dose measured in micrograms can be enough to stop someone breathing, which is why it causes so many accidental deaths when it shows up in the street drug supply.
This page explains what fentanyl is, how it affects the body, how to recognize addiction, what to do during an overdose, and how treatment works in Canada. If you are worried about your own use or someone you love, there is a way out, and help is available across Ontario and the rest of the country.
What fentanyl is used for
Doctors prescribe fentanyl for serious pain, often after surgery or for people living with advanced cancer. In a medical setting it is given as a slow-release skin patch, a lozenge, an injection, or a nasal spray. Brand names include Duragesic, Actiq, and Sublimaze.
Its strength is the reason for the slow-release patch. Fentanyl can be about 100 times stronger than morphine and roughly 50 times stronger than heroin. Used carefully under supervision, it controls pain that weaker drugs cannot. Outside that setting, the same strength makes it dangerous.
Why street fentanyl is so dangerous
Most fentanyl deaths are accidental. Illegally made fentanyl is often mixed into other drugs such as heroin, cocaine, or counterfeit pills, so people take it without knowing it is there. Two pills that look identical can contain very different amounts, and there is no way to judge a safe dose by sight.
The Public Health Agency of Canada attributes the large majority of opioid-related deaths in recent years to fentanyl and related substances. The death of the musician Prince in 2016 brought wider attention to how quickly it can kill, but most of the people lost are not famous, and many never intended to take fentanyl at all.
What fentanyl does to the body
Opioids attach to receptors in the brain that control pain and emotion. In the right dose, fentanyl reduces pain. In too high a dose, it slows breathing and heart rate until the brain is starved of oxygen, which can lead to coma or death.
Because it is so potent, dependence can form fast. Someone may feel they need the drug after only a short period of use. Common effects of recreational use include a brief intense high, drowsiness, confusion, nausea, and slowed breathing. You can read more about this drug class on our opioid addiction page.
Signs of fentanyl addiction
Opioid addiction does not always start on the street. It often begins with a prescription that slowly stops working the way it did, leading a person to take more, or to look for something stronger.
Signs worth paying attention to include:
- Taking more than a doctor prescribed, or taking opioids that were not prescribed
- Using opioids to get ahead of pain before it starts
- Getting the same prescription from several doctors
- Money going missing or constant money problems
- Withdrawing from family, secrecy, and mood swings
- Changes in sleep
If several of these sound familiar, it is worth talking to someone. Our drug and alcohol helpline can help you figure out the next step, and an intervention is sometimes the right way to start that conversation.
Fentanyl overdose: what it looks like and what to do
Call 911 first. An overdose is a medical emergency.
Signs of an opioid overdose include:
- Slow, shallow, or stopped breathing
- Blue or grey lips and nails, or blue inside the lips for people with darker skin
- Loss of consciousness and very small pupils
- Cold, clammy skin
- Gurgling or snoring sounds
Naloxone reverses an opioid overdose if it is given in time. It blocks opioid receptors and can restart normal breathing within minutes. Because fentanyl is so strong, more than one dose may be needed. Free naloxone kits are available at pharmacies and public health units across most of Canada. Read more in our guide to naloxone. Canada’s Good Samaritan Drug Overdose Act offers some legal protection to people who call for help during an overdose.
Fentanyl withdrawal
Withdrawal is not usually life threatening on its own, but it is hard, and the fear of it keeps many people using. Because fentanyl leaves the body quickly, symptoms can start within hours of the last dose. Our complete guide to the fentanyl withdrawal timeline and symptoms walks through what to expect day by day and how to get through it safely.
They can include muscle and bone aches, trouble sleeping, sweating and chills, nausea, vomiting and diarrhea, a racing heart, and shaking. Medically supervised detox makes this safer and more bearable, and it is the recommended way to come off opioids rather than quitting alone.
How fentanyl addiction is treated
Treatment usually combines medication with counselling.
Opioid agonist therapy uses methadone or buprenorphine to ease withdrawal and cravings without the intense high. These are still opioids, but they are taken in steady, controlled doses so a person can stabilize and slowly taper down. You can read more on our methadone treatment page.
Alongside medication, counselling and rehab programs help people understand what drives their use and build habits that hold up after treatment ends. Recovery rarely follows a straight line, and the people who do best are usually the ones who get support for the long haul, including the family members and caregivers around them.
Getting help in Ontario and across Canada
You do not have to sort this out by yourself. We can match you with detox, opioid agonist therapy, and residential or outpatient treatment near you. Start with our Ontario rehab directory or speak to an advisor through our helpline.
Frequently asked questions
Can you get addicted to fentanyl after one use?
Not usually after a single dose, but dependence can build quickly with repeated use because of how potent it is.
How much fentanyl is dangerous?
There is no reliable safe amount with street fentanyl, because the strength of any given pill or powder is unknown. Even a very small amount can be fatal.
Is fentanyl legal in Canada?
Pharmaceutical fentanyl is legal when prescribed by a doctor. Illegally made fentanyl, and possession without a prescription, is not.
