Opioids and fentanyl

What they do

What opioids are, how they feel, and why fentanyl is different.

Opioids are drugs that relieve pain: codeine, morphine, oxycodone, hydromorphone, fentanyl, and heroin among them. They're medicines, and they're also made and sold illegally.

What they can do

• Pain: Pain relief: it's what they're for.
• High: Euphoria, which is part of why they're misused.
• Heavy: Drowsiness, dizziness and confusion.
• Sick: Nausea, vomiting and constipation.
• Breathing: Slower breathing, slowing further as the dose rises past what the body can handle.

Why fentanyl changed everything

Fentanyl is 20 to 40 times stronger than heroin and 100 times stronger than morphine, and a few grains can be enough to kill. It has no smell or taste, and it's mixed into heroin, cocaine and meth and pressed into fake pills made to look like oxycodone or Xanax, often without people knowing. Life-threatening effects can start within 2 minutes.

What's happening in the brain

A breathing rhythm slowed, a reward brake released, and a body that adapts. The model lights each one as you read.

The breathing rhythm

Every breath starts in a tiny cluster of neurons in the brainstem, the preBötzinger complex. In mice, its mu-opioid receptors are what let opioids depress breathing: remove them there and breathing was largely protected, while pain relief was untouched. It's why an overdose kills: breathing slows, then stops.

The reward brake

In the ventral tegmental area, dopamine neurons are normally held in check by neighbouring GABA neurons. Opioids silence those GABA neurons, releasing the dopamine cells, which send their signal on to the nucleus accumbens, the pathway behind reward and motivation.

With regular use the body adapts. Tolerance builds, so the same dose does less, and the body comes to depend on a steady supply, so stopping brings withdrawal. Both happen even with prescribed opioids. With fentanyl, dependence can develop within weeks of regular use.

Tolerance disappears faster than people think

Tolerance is lost after even a few days without opioids. Go back to a previous dose after a break — after detox, treatment, hospital or jail — and it can be an overdose.

The crisis in Canada

A poisoned drug supply, in numbers.

• 57,509 deaths since 2016: Apparent opioid poisoning deaths in Canada, January 2016 to March 2026.
• 96% were accidental: Of deaths in early 2026.
• 62% also involved a stimulant: Such as cocaine or meth, in early 2026.

In the first three months of 2026, 1,354 people died (a preliminary count); 70% were men. Fentanyl was involved in 36% of deaths and drugs made to mimic it, fentanyl analogues, in 70%. Fentanyl and drugs like it are increasingly found in other illegal drugs, so people often can't tell what, or how much, they're taking.

Recognising and reversing an overdose

The signs, the three steps, and why calling is safe.

Signs of an opioid overdose

• Can't be woken, even when shaken or shouted at.
• Slow, weak or no breathing; choking, gurgling or snoring sounds.
• Blue, purple or grey lips or nails; cold, clammy skin.
• Very small pupils.
• Extreme drowsiness, confusion, trouble walking or talking.

What to do

1. Call 911: Right away. An overdose is always an emergency.
2. Give naloxone: If you have it. It starts working in about 2 minutes; if there's no response after 2–3 minutes, give another dose.
3. Stay: Until help arrives. Follow the 911 operator and the instructions in the kit.

Naloxone wears off

Naloxone lasts about 30 to 120 minutes, and many opioids last longer, so someone can stop breathing again after they wake up. That's why calling 911 and staying still matters after it works.

Calling for help is protected

Since 2017, the Good Samaritan Drug Overdose Act has protected the person who calls 911, the person overdosing and anyone else there from charges of simple drug possession, and from breaching conditions about it in bail, probation or parole. It doesn't cover trafficking or outstanding warrants.

Carry a kit. Naloxone nasal spray and injection kits are at most pharmacies without a prescription, and free in most provinces and territories, including Ontario. It works on fentanyl overdoses too.

Lowering the risk

For anyone who uses, or is around people who do.

What lowers the risk

• Never use alone: have someone with you, or use an overdose prevention service.
• Don't mix opioids with alcohol or sedatives like benzodiazepines.
• After any break, your tolerance is lower: a dose you used to take can now kill.
• Assume any pill not from a pharmacy could contain fentanyl.
• Test strips can help, but a negative isn't a guarantee: they can miss stronger fentanyl-like drugs such as carfentanil.
• Carry naloxone, and make sure the people around you know where it is.

Dependence and treatment

Opioid use disorder is a medical condition, and its treatments save lives.

Opioid use disorder changes the brain and body in ways that make it hard to stop: cravings, using despite harm, opioids taking over thoughts and life. Not everyone who uses opioids develops it, and it's treatable. Even a short prescription carries some risk: the longer the first supply, the likelier people are to still be on opioids a year later, rising most sharply after day 5 and day 31.

• Methadone (A daily liquid opioid agonist, usually taken under supervision.): It prevents withdrawal and cuts cravings. Deaths ran at 11.3 per 1,000 people a year in methadone treatment against 36.1 out of it.
• Buprenorphine (Including buprenorphine/naloxone (Suboxone): a daily film or tablet, or a monthly injection.): Deaths ran at 4.3 per 1,000 people a year in treatment against 9.5 out of it.
• Slow-release morphine and injectable treatment (For people whom methadone or buprenorphine haven't helped.): Slow-release oral morphine, or supervised injectable diamorphine or hydromorphone; availability varies by province.
• Stopping abruptly (Going cold turkey, alone.): It can bring severe withdrawal and cravings that often lead back to use, at a lower tolerance, raising the risk of overdose.

The riskiest weeks

The first weeks of starting methadone, and the time just after leaving any treatment, carry particularly high risk of death. Keep naloxone close then.

Treatment works best alongside support: family, friends, peers, and a care team for housing, mental health and pain.

Talking about it

Words can push people to use alone. These ones help.

• Instead of "He's just an addict.", try "He's a person who uses drugs, and he has a treatable condition.". Slang like 'addict' and 'junkie' feeds stigma, and stigma makes people hide their use, use alone, and avoid help.
• Instead of "If you call 911, we'll all get arrested.", try "Call. The Good Samaritan Act protects us from possession charges.". It protects everyone there from simple possession charges when someone calls for help.
• Instead of "Methadone is just swapping one drug for another.", try "It's treatment, and it keeps people alive.". People in methadone treatment died at about a third of the rate of people out of it.

Put it into practice

Five real situations. Choose what you'd do, and see why.

• At a party, a friend is slumped on the couch. She won't wake when you shout, her lips are bluish, and she's making snoring sounds. What do you do? Call 911, give naloxone if anyone has it, and stay with her. Unresponsiveness, blue lips and snoring sounds are overdose signs; call 911, give naloxone, stay.
• Someone is overdosing, but your friend says not to call 911 because everyone has drugs on them. What's true? The Good Samaritan Act protects everyone there from simple possession charges, so call. It covers the caller, the person overdosing and others present.
• You give naloxone. Two minutes later he wakes up, says he's fine and wants to leave before the ambulance comes. What should happen? Stay with him until help arrives: naloxone can wear off before the opioid does. Naloxone lasts about 30–120 minutes, and opioids often last longer, so breathing can stop again.
• Your cousin just finished a month in detox. She says if she uses once, she'll just take her old amount. Why is that so dangerous? Her tolerance is gone: her old dose could now be an overdose. Tolerance is lost after even a few days off, and restarting at a previous dose raises overdose risk.
• A friend offers you a "Percocet" he bought from someone online to help you sleep. What's the risk? Pills not from a pharmacy can be counterfeit and contain fentanyl, and a few grains can kill. Counterfeit pills made to look like oxycodone often contain fentanyl, and a few grains can be enough to kill.